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Re: TX802 troubleshooting

 


Hi PeWe,

Op zo 5 feb. 2023 om 11:46 schreef PeWe <ha-pewe@...>:
Since my friend (tech) and me started to do inhouse repairs and service for all my gear many years ago, we never ever had to replace ALL capacitors in any machine, regardless of brand and type.
You have more experience here than me but this is also my experience. Only once have I had to do a recap of a power supply, and that was a JD990 that was failing to boot, and it had a clear 50Hz ripple on its 5V line.
?
Necessary service was usually battery change and soldering in battery holders, replacing a by roadies physically damaged display, tact switch replacements and PSU overhaul for REV-7.
Big fan of tact switch replacement. Not a fan of battery holders because the new battery should last 10-20 years and a holder can fail mechanically. Soldering it in is more reliable IMO.
?
Ribbon cables and sockets are often culprits ...
When cables and sockets aren?t available anymore, removing socket and solder the ribbon directly to the board was the simple solution.
Funny enough this is why I also think batteries should be soldered. :)

Because of how the TX802 is organized this cannot be a cable problem. The fault is happening on the main board and it does not involve data that goes through a cable.

The ROMs sit in non-precision sockets so that is suspicious. But if either of the CPUs was reading corrupt ROM instruction data it would be very likely that the CPU would crash. Still, replacing the ROMs is relatively cheap and non-destructive so I'm willing to try it.
?
So, PSU and ALL connections (soldering joints, sockets, plugs, ribbon cables) have to work 100% perfect before replacing anything else.
In an earlier email I wrote I suddenly saw a 1.5V ripple on the 5V line. It turned out that it was coming from a USB power supply sitting in the same power strip as the TX802. When I unplug that USB power supply the ripple goes away, and the bad behavior stays. I probably don't need to recap the PSU after all.

Finding the cause of failure is the most difficult and time consuming,- and I won?t replace anything before being sure what it really is.
Thank you, I agree very strongly with this. This is why I have been pushing back on blanket suggestions of recaps etc.

The common buyer and user of used vintage gear is often not able to identify cause of failure because of lack of tech skills and missing tools for diagnostics (and repair).
To save time it?s sometimes better buying a 2nd used machine and swap boards, then use the better one for work and the other for parts in future.
Yes it seems to be common for people to be enthusiastic and overestimate their chances of success. I know from experience what you are talking about.

I have sunk a lot of time into a broken DX7II that I had to give up on; I ended up buying another one and keeping the broken one for parts. I have experience with fault finding and repair on analog synthesizers. I know that my chances of success are much lower on a digital synth like the TX802 because of the proprietary IC's and because I don't have a logic analyzer. With an analog synth I can chase the control voltages using a single oscilloscope probe but in a digital synth the "control voltages" are byte streams and for that you need a logic analyzer.

I took on this challenge anyway because the TX802 service manual has a lot of good information, including a full schematic, and because I enjoy the fault finding.

My best guess at the moment is a partially broken SRAM on the secondary CPU. The SRAM probablye does not contain instructions so corrupt data would not immediately cause a crash. It's not expensive to replace and I have a heat gun so I will be able to neatly remove the old SRAM IC.

I see activity with my scope on all the SRAM pins that should have activity so I don't think it's a broken trace. Also, shorts on the address or data lines would corrupt data read from ROM too and then there would be a crash.
?
Cheers, Jacob


Re: TX802 troubleshooting

 


If you have to replace a bad cap on a PCB...., what makes you think that the other ones, with same age and build quality, are in perfect working condition?

In my experience, replacing all capacitors, beyond the psu ones, makes a night and day difference not only to my ears, you get a trustable working machine with glorious sound for years to come.

It's about the sound, in the end, and reliability.

This is my way, and not necessarily the way for everybody.

As example, JP-8000 may put some light.





Peace
José Juan?







El dom, 5 feb 2023, 12:02, Martin Tarenskeen <m.tarenskeen@...> escribió:
On Feb 4, 2023, at 5:31, José Juan wrote:

"Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear."

From reactions from some of the more experienced experts here I think I can conclude that statement highly exxagerated?

MT



Verzonden vanaf mijn Huawei mobiele telefoon


-------- Oorspronkelijk bericht --------
Onderwerp: Re: [YamahaDX] TX802 troubleshooting
Van: PeWe
Aan: [email protected],danforcz@...
Cc:


Hi Daniel !

I agree 100%!

Since my friend (tech) and me started to do inhouse repairs and service for all my gear many years ago, we never ever had to replace ALL capacitors in any machine, regardless of brand and type.
Especially the old Yamaha gear was and still is very reliable.
I?m 1st owner,- and my TX816 is still intact, my DX7mkII never failed and younger devices like TG77 and TG500 work flawlessly.
Needles to say the same rules for the KX-76, KX-5, D-1500 and REV-7.
Necessary service was usually battery change and soldering in battery holders, replacing a by roadies physically damaged display, tact switch replacements and PSU overhaul for REV-7.
The TX816 might need a single new LED on one of the TF-1 modules and I think about replacing the original PSU w/ this one (if at all) ...


WHEN we had to replace aged capacitors in other gear,- these belonged to the PSU always.
AKAI S-1000 PSU capacitors leaked in both machines, S-1100 PSUs are different and didn?t.

Ribbon cables and sockets are often culprits ...
When cables and sockets aren?t available anymore, removing socket and solder the ribbon directly to the board was the simple solution.
That happened w/ a Oberheim DPX-1 not playing a tone, not loading disks and showing cryptic stuff in display.

So, PSU and ALL connections (soldering joints, sockets, plugs, ribbon cables) have to work 100% perfect before replacing anything else.

Well, this thread is about TX802 which I don?t use, but I?d say, repair and service on electronic gear of that era isn?t soooo special and urgently depending on brand/model.
Finding the cause of failure is the most difficult and time consuming,- and I won?t replace anything before being sure what it really is.
The common buyer and user of used vintage gear is often not able to identify cause of failure because of lack of tech skills and missing tools for diagnostics (and repair).
To save time it?s sometimes better buying a 2nd used machine and swap boards, then use the better one for work and the other for parts in future.

:-)

P.

Am 04.02.2023 um 03:37 schrieb Daniel Forró via :
It is not recommended to replace all caps, only the bad ones. Service experts say: If it works, leave it so.

Daniel Forró

On Feb 4, 2023, at 5:31, José Juan <josejuangallego@...> wrote:

Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.




Virenfrei.




Re: TX802 troubleshooting

 

On Feb 4, 2023, at 5:31, José Juan wrote:

"Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear."

From reactions from some of the more experienced experts here I think I can conclude that statement highly exxagerated?

MT



Verzonden vanaf mijn Huawei mobiele telefoon


-------- Oorspronkelijk bericht --------
Onderwerp: Re: [YamahaDX] TX802 troubleshooting
Van: PeWe
Aan: [email protected],danforcz@...
Cc:


Hi Daniel !

I agree 100%!

Since my friend (tech) and me started to do inhouse repairs and service for all my gear many years ago, we never ever had to replace ALL capacitors in any machine, regardless of brand and type.
Especially the old Yamaha gear was and still is very reliable.
I?m 1st owner,- and my TX816 is still intact, my DX7mkII never failed and younger devices like TG77 and TG500 work flawlessly.
Needles to say the same rules for the KX-76, KX-5, D-1500 and REV-7.
Necessary service was usually battery change and soldering in battery holders, replacing a by roadies physically damaged display, tact switch replacements and PSU overhaul for REV-7.
The TX816 might need a single new LED on one of the TF-1 modules and I think about replacing the original PSU w/ this one (if at all) ...


WHEN we had to replace aged capacitors in other gear,- these belonged to the PSU always.
AKAI S-1000 PSU capacitors leaked in both machines, S-1100 PSUs are different and didn?t.

Ribbon cables and sockets are often culprits ...
When cables and sockets aren?t available anymore, removing socket and solder the ribbon directly to the board was the simple solution.
That happened w/ a Oberheim DPX-1 not playing a tone, not loading disks and showing cryptic stuff in display.

So, PSU and ALL connections (soldering joints, sockets, plugs, ribbon cables) have to work 100% perfect before replacing anything else.

Well, this thread is about TX802 which I don?t use, but I?d say, repair and service on electronic gear of that era isn?t soooo special and urgently depending on brand/model.
Finding the cause of failure is the most difficult and time consuming,- and I won?t replace anything before being sure what it really is.
The common buyer and user of used vintage gear is often not able to identify cause of failure because of lack of tech skills and missing tools for diagnostics (and repair).
To save time it?s sometimes better buying a 2nd used machine and swap boards, then use the better one for work and the other for parts in future.

:-)

P.

Am 04.02.2023 um 03:37 schrieb Daniel Forró via groups.io:
It is not recommended to replace all caps, only the bad ones. Service experts say: If it works, leave it so.

Daniel Forró

On Feb 4, 2023, at 5:31, José Juan <josejuangallego@...> wrote:

Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.




Virenfrei.


Re: TX802 troubleshooting

 

开云体育

Hi Daniel !

I agree 100%!

Since my friend (tech) and me started to do inhouse repairs and service for all my gear many years ago, we never ever had to replace ALL capacitors in any machine, regardless of brand and type.
Especially the old Yamaha gear was and still is very reliable.
I?m 1st owner,- and my TX816 is still intact, my DX7mkII never failed and younger devices like TG77 and TG500 work flawlessly.
Needles to say the same rules for the KX-76, KX-5, D-1500 and REV-7.
Necessary service was usually battery change and soldering in battery holders, replacing a by roadies physically damaged display, tact switch replacements and PSU overhaul for REV-7.
The TX816 might need a single new LED on one of the TF-1 modules and I think about replacing the original PSU w/ this one (if at all) ...


WHEN we had to replace aged capacitors in other gear,- these belonged to the PSU always.
AKAI S-1000 PSU capacitors leaked in both machines, S-1100 PSUs are different and didn?t.

Ribbon cables and sockets are often culprits ...
When cables and sockets aren?t available anymore, removing socket and solder the ribbon directly to the board was the simple solution.
That happened w/ a Oberheim DPX-1 not playing a tone, not loading disks and showing cryptic stuff in display.

So, PSU and ALL connections (soldering joints, sockets, plugs, ribbon cables) have to work 100% perfect before replacing anything else.

Well, this thread is about TX802 which I don?t use, but I?d say, repair and service on electronic gear of that era isn?t soooo special and urgently depending on brand/model.
Finding the cause of failure is the most difficult and time consuming,- and I won?t replace anything before being sure what it really is.
The common buyer and user of used vintage gear is often not able to identify cause of failure because of lack of tech skills and missing tools for diagnostics (and repair).
To save time it?s sometimes better buying a 2nd used machine and swap boards, then use the better one for work and the other for parts in future.

:-)

P.

Am 04.02.2023 um 03:37 schrieb Daniel Forró via groups.io:
It is not recommended to replace all caps, only the bad ones. Service experts say: If it works, leave it so.

Daniel Forró

On Feb 4, 2023, at 5:31, José Juan <josejuangallego@...> wrote:

Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.




Virenfrei.


Re: TX802 troubleshooting

 

开云体育

Here is that alternative version together with patch names:?


Daniel Forró


On Feb 5, 2023, at 11:34, Daniel Forró via <danforcz@...> wrote:

You can find Eprom data also here:


If it doesn’t work, I can send you it as well.

BTW, one of Eprom keeps preset patches data, somebody did different selection. I have this version, too.

Good luck.

Daniel Forró



On Feb 5, 2023, at 4:04, contact@... wrote:

Hi Grant,


Op za 4 feb. 2023 om 14:54 schreef grantpbt <grantbt@...>:

Two things to avoid: dismissing input from Daniel Forro and making
assumptions. This is first and foremost electronic troubleshooting.
I am not dismissing Daniel's input, I am reacting to his suggestions.
I really appreciate that Daniel refers to actual problems that others
have had with the TX802, such as the output muting transistors.

Check all the Power Supply voltages. I have seen an increasing number of
Yamaha PSU failures which are happening because a LOT of the Yamaha
designs use a Switch Mode PS. I have been able to repair some of the
PSUs, but not all. There are many threads online discussing this or that
synth or effects unit needing PSU repairs and various successes and
failures.
Logical analysis clearly shows that the problem is in the digital
domain. Everything from the EGM chip on down functions correctly. So
the only power line that matters here is the 5V digital supply. I have
checked that, with an oscilloscope, and it looks fine.

Take a look at the block diagram of the TX802 on page 4/5 of the
service manual. Everything from the EGM on down is working correctly.
That also implies that the "master oscillator" works correctly: if it
didn't, you would never get clean sine waves (at the correct pitch!)
out of the outputs.

If you look on the left of the block diagram you see that the "master
MPU" runs on its own clock crystal. It is responsible for receiving
MIDI. If that clock was not running, or not running at the right rate,
incoming MIDI data would be garbled. MIDI works fine so I know that
clock crystal is fine.

I am not pro-cap replacement, but as far as the PSU is concerned this is
a common problem with them.
I agree. But this just doesn't look like a PSU problem. Remember that
the main CPU works fine. The synth responds to MIDI, I can use all the
buttons in the interface, the display works, there is no garbled text
in it. It does not crash.

The BIN files are everywhere.
I wish that were true. I have spent a lot of time looking already. The
only source I can find for the BIN files is
, where you have
to pay $10 a pop.

Do you know where to find them? The ROMs are called XB223, XB224 and XB536.

I agree that a byte for byte comparison is the right thing to do but I
only have those checksums. And unfortunately, that page does not have
the checksums for TX802 v1.2, which is what I have.


Reseating the EPROM was a good move. Sockets get dirty. Bad connections
cause a myriad of problems. Look at the schematics and Service Manual.
Thanks, I have spent a lot of time looking at the service manual
before I even posted here. That is how I know about the EGM and OPS2
chips.

Most of the Yamaha FM products have a huge similarity and some of the
Service Manuals are very helpful, others less so.
Thanks, I agree.

The DX7II is a close relative of the TX802. I have spent a lot of time
reading its service manual too. In spite of them having the same sound
generator ICs, the architectures of the two are different. In the
DX7II the primary CPU drives the EGM/OPS2 and the secondary CPU
handles keyboard inputs etc. In the TX802, the secondary CPU drives
the EGM/OPS. This makes the flow of data quite different. You can
clearly see this if you compare the block diagrams in the respective
service manuals.

The DX7/DX9 service manual has some high level information about the
EGS and OPS sound generator IC's. The IC's in the TX802/DX7II are
different however. For example, the old EGS has an 8 bit input address
bus. The new EGM has only a 5 bit address bus. We have to guess what
the inputs to the EGM exactly are.

The weird thing is that the EGM is getting input data that is mostly
correct (amplitude envelope rates are correct, amplitude L4 is
correct, pitch EG works correctly) and only incorrect in some places:
the output level and L1/L2/L3 of the operator amplitude envelopes.

I see no evidence on my scope that they are broken, but I think I will
try replacing the RAM chip of the secondary CPU and the 74HC138
address decoder that enables the EGM and OPS2 IC's. If I can get hold
of the bin files I will also replace the ROMs because it's easy to do.

Jacob









Re: TX802 troubleshooting

 

开云体育

You can find Eprom data also here:


If it doesn’t work, I can send you it as well.

BTW, one of Eprom keeps preset patches data, somebody did different selection. I have this version, too.

Good luck.

Daniel Forró



On Feb 5, 2023, at 4:04, contact@... wrote:

Hi Grant,


Op za 4 feb. 2023 om 14:54 schreef grantpbt <grantbt@...>:

Two things to avoid: dismissing input from Daniel Forro and making
assumptions. This is first and foremost electronic troubleshooting.
I am not dismissing Daniel's input, I am reacting to his suggestions.
I really appreciate that Daniel refers to actual problems that others
have had with the TX802, such as the output muting transistors.

Check all the Power Supply voltages. I have seen an increasing number of
Yamaha PSU failures which are happening because a LOT of the Yamaha
designs use a Switch Mode PS. I have been able to repair some of the
PSUs, but not all. There are many threads online discussing this or that
synth or effects unit needing PSU repairs and various successes and
failures.
Logical analysis clearly shows that the problem is in the digital
domain. Everything from the EGM chip on down functions correctly. So
the only power line that matters here is the 5V digital supply. I have
checked that, with an oscilloscope, and it looks fine.

Take a look at the block diagram of the TX802 on page 4/5 of the
service manual. Everything from the EGM on down is working correctly.
That also implies that the "master oscillator" works correctly: if it
didn't, you would never get clean sine waves (at the correct pitch!)
out of the outputs.

If you look on the left of the block diagram you see that the "master
MPU" runs on its own clock crystal. It is responsible for receiving
MIDI. If that clock was not running, or not running at the right rate,
incoming MIDI data would be garbled. MIDI works fine so I know that
clock crystal is fine.

I am not pro-cap replacement, but as far as the PSU is concerned this is
a common problem with them.
I agree. But this just doesn't look like a PSU problem. Remember that
the main CPU works fine. The synth responds to MIDI, I can use all the
buttons in the interface, the display works, there is no garbled text
in it. It does not crash.

The BIN files are everywhere.
I wish that were true. I have spent a lot of time looking already. The
only source I can find for the BIN files is
, where you have
to pay $10 a pop.

Do you know where to find them? The ROMs are called XB223, XB224 and XB536.

I agree that a byte for byte comparison is the right thing to do but I
only have those checksums. And unfortunately, that page does not have
the checksums for TX802 v1.2, which is what I have.


Reseating the EPROM was a good move. Sockets get dirty. Bad connections
cause a myriad of problems. Look at the schematics and Service Manual.
Thanks, I have spent a lot of time looking at the service manual
before I even posted here. That is how I know about the EGM and OPS2
chips.

Most of the Yamaha FM products have a huge similarity and some of the
Service Manuals are very helpful, others less so.
Thanks, I agree.

The DX7II is a close relative of the TX802. I have spent a lot of time
reading its service manual too. In spite of them having the same sound
generator ICs, the architectures of the two are different. In the
DX7II the primary CPU drives the EGM/OPS2 and the secondary CPU
handles keyboard inputs etc. In the TX802, the secondary CPU drives
the EGM/OPS. This makes the flow of data quite different. You can
clearly see this if you compare the block diagrams in the respective
service manuals.

The DX7/DX9 service manual has some high level information about the
EGS and OPS sound generator IC's. The IC's in the TX802/DX7II are
different however. For example, the old EGS has an 8 bit input address
bus. The new EGM has only a 5 bit address bus. We have to guess what
the inputs to the EGM exactly are.

The weird thing is that the EGM is getting input data that is mostly
correct (amplitude envelope rates are correct, amplitude L4 is
correct, pitch EG works correctly) and only incorrect in some places:
the output level and L1/L2/L3 of the operator amplitude envelopes.

I see no evidence on my scope that they are broken, but I think I will
try replacing the RAM chip of the secondary CPU and the 74HC138
address decoder that enables the EGM and OPS2 IC's. If I can get hold
of the bin files I will also replace the ROMs because it's easy to do.

Jacob





Re: TX802 troubleshooting

 

I should have included some sound samples in my first post because
they make it clearer what is going on. Let me post them now.

Here is the sound of an init patch:


Init patch, with the algorithm changed to 32:


Init patch, with slow R1 and R4 rates on all operators:


Init patch with some pitch envelope:


Note how there is silence before and after the notes. And that this TX
can make clean sounds if you choose an algorithm without any
modulators.


Op za 4 feb. 2023 om 21:33 schreef contact via groups.io
<contact@...>:


José, the caps on my TX802 all look like new. No bulging, no leaking.
There would be nothing to see in a photo.

That does not mean they are all still good though. That 1.5V ripple is
not supposed to be there.

Op za 4 feb. 2023 om 21:16 schreef José Juan <josejuangallego@...>:

"I will recap the PSU."

-> essential starting point imho.

Please take photos of retired bad caps.

Here you can see what I found on my TX16W:



Good luck and go on!
José Juan









Re: TX802 troubleshooting

 

José, the caps on my TX802 all look like new. No bulging, no leaking.
There would be nothing to see in a photo.

That does not mean they are all still good though. That 1.5V ripple is
not supposed to be there.

Op za 4 feb. 2023 om 21:16 schreef José Juan <josejuangallego@...>:


"I will recap the PSU."

-> essential starting point imho.

Please take photos of retired bad caps.

Here you can see what I found on my TX16W:



Good luck and go on!
José Juan








Re: TX802 troubleshooting

 

"I will recap the PSU."

-> essential starting point imho.

Please take photos of retired bad caps.

Here you can see what I found on my TX16W:



Good luck and go on!
José Juan?









Re: TX802 troubleshooting

 

Thank you John!

I wouldn't say I'm fighting a problem: I'm trying to solve an
interesting challenge. For me this is fun.

Grant, thank you for insisting on looking at the PSU. I took a closer
look and I see a recurring ripple of about 1.5V peak to peak occurring
at about 25 kHz. Somehow I remember that that is the frequency of the
switch mode PSU in these Yamaha boxes but I can't find the source.
(There are PSU details in the TX7 service manual but they don't
mention the switching frequency.)

I think I missed this ripple earlier on because I was looking at the
address lines, and my oscilloscope trigger level was set too low to
catch this ripple. I was trying to see the logic transitions.

Wherever this ripple is coming from, 1.5V is unacceptable. I will recap the PSU.

Op za 4 feb. 2023 om 20:29 schreef John Williston <john@...>:


I thought I would write a quick note of encouragement for Jacob. I’m sorry you’re fighting such an odd problem, but as someone who reads the list, I appreciate your posting the details. This is a learning experience for all of us watching.


On Sat, Feb 4 2023 at 11:04, contact <contact@...> wrote:

Hi Grant,

Op za 4 feb. 2023 om 14:54 schreef grantpbt <grantbt@...>:
Two things to avoid: dismissing input from Daniel Forro and making assumptions. This is first and foremost electronic troubleshooting.

I am not dismissing Daniel's input, I am reacting to his suggestions. I really appreciate that Daniel refers to actual problems that others have had with the TX802, such as the output muting transistors.

Check all the Power Supply voltages. I have seen an increasing number of Yamaha PSU failures which are happening because a LOT of the Yamaha designs use a Switch Mode PS. I have been able to repair some of the PSUs, but not all. There are many threads online discussing this or that synth or effects unit needing PSU repairs and various successes and failures.

Logical analysis clearly shows that the problem is in the digital domain. Everything from the EGM chip on down functions correctly. So the only power line that matters here is the 5V digital supply. I have checked that, with an oscilloscope, and it looks fine.

Take a look at the block diagram of the TX802 on page 4/5 of the service manual. Everything from the EGM on down is working correctly. That also implies that the "master oscillator" works correctly: if it didn't, you would never get clean sine waves (at the correct pitch!) out of the outputs.

If you look on the left of the block diagram you see that the "master MPU" runs on its own clock crystal. It is responsible for receiving MIDI. If that clock was not running, or not running at the right rate, incoming MIDI data would be garbled. MIDI works fine so I know that clock crystal is fine.

I am not pro-cap replacement, but as far as the PSU is concerned this is a common problem with them.

I agree. But this just doesn't look like a PSU problem. Remember that the main CPU works fine. The synth responds to MIDI, I can use all the buttons in the interface, the display works, there is no garbled text in it. It does not crash.

The BIN files are everywhere.

I wish that were true. I have spent a lot of time looking already. The only source I can find for the BIN files is
, where you have to pay $10 a pop.

Do you know where to find them? The ROMs are called XB223, XB224 and XB536.

I agree that a byte for byte comparison is the right thing to do but I only have those checksums. And unfortunately, that page does not have the checksums for TX802 v1.2, which is what I have.

Reseating the EPROM was a good move. Sockets get dirty. Bad connections cause a myriad of problems. Look at the schematics and Service Manual.

Thanks, I have spent a lot of time looking at the service manual before I even posted here. That is how I know about the EGM and OPS2 chips.

Most of the Yamaha FM products have a huge similarity and some of the Service Manuals are very helpful, others less so.

Thanks, I agree.

The DX7II is a close relative of the TX802. I have spent a lot of time reading its service manual too. In spite of them having the same sound generator ICs, the architectures of the two are different. In the DX7II the primary CPU drives the EGM/OPS2 and the secondary CPU handles keyboard inputs etc. In the TX802, the secondary CPU drives the EGM/OPS. This makes the flow of data quite different. You can clearly see this if you compare the block diagrams in the respective service manuals.

The DX7/DX9 service manual has some high level information about the EGS and OPS sound generator IC's. The IC's in the TX802/DX7II are different however. For example, the old EGS has an 8 bit input address bus. The new EGM has only a 5 bit address bus. We have to guess what the inputs to the EGM exactly are.

The weird thing is that the EGM is getting input data that is mostly correct (amplitude envelope rates are correct, amplitude L4 is correct, pitch EG works correctly) and only incorrect in some places: the output level and L1/L2/L3 of the operator amplitude envelopes.

I see no evidence on my scope that they are broken, but I think I will try replacing the RAM chip of the secondary CPU and the 74HC138 address decoder that enables the EGM and OPS2 IC's. If I can get hold of the bin files I will also replace the ROMs because it's easy to do.

Jacob


Re: TX802 troubleshooting

 

开云体育

I thought I would write a quick note of encouragement for Jacob. I’m sorry you’re fighting such an odd problem, but as someone who reads the list, I appreciate your posting the details. This is a learning experience for all of us watching.


On Sat, Feb 4 2023 at 11:04, contact <contact@...> wrote:

Hi Grant,

Op za 4 feb. 2023 om 14:54 schreef grantpbt <grantbt@...>:
>

Two things to avoid: dismissing input from Daniel Forro and making assumptions. This is first and foremost electronic troubleshooting.

I am not dismissing Daniel's input, I am reacting to his suggestions. I really appreciate that Daniel refers to actual problems that others have had with the TX802, such as the output muting transistors.

Check all the Power Supply voltages. I have seen an increasing number of Yamaha PSU failures which are happening because a LOT of the Yamaha designs use a Switch Mode PS. I have been able to repair some of the PSUs, but not all. There are many threads online discussing this or that synth or effects unit needing PSU repairs and various successes and failures.

Logical analysis clearly shows that the problem is in the digital domain. Everything from the EGM chip on down functions correctly. So the only power line that matters here is the 5V digital supply. I have checked that, with an oscilloscope, and it looks fine.

Take a look at the block diagram of the TX802 on page 4/5 of the service manual. Everything from the EGM on down is working correctly. That also implies that the "master oscillator" works correctly: if it didn't, you would never get clean sine waves (at the correct pitch!) out of the outputs.

If you look on the left of the block diagram you see that the "master MPU" runs on its own clock crystal. It is responsible for receiving MIDI. If that clock was not running, or not running at the right rate, incoming MIDI data would be garbled. MIDI works fine so I know that clock crystal is fine.

I am not pro-cap replacement, but as far as the PSU is concerned this is a common problem with them.

I agree. But this just doesn't look like a PSU problem. Remember that the main CPU works fine. The synth responds to MIDI, I can use all the buttons in the interface, the display works, there is no garbled text in it. It does not crash.

The BIN files are everywhere.

I wish that were true. I have spent a lot of time looking already. The only source I can find for the BIN files is
http://www.musictechnologiesgroup.com/mtg_eproms.htm, where you have to pay $10 a pop.

Do you know where to find them? The ROMs are called XB223, XB224 and XB536.

I agree that a byte for byte comparison is the right thing to do but I only have those checksums. And unfortunately, that page does not have the checksums for TX802 v1.2, which is what I have.

Reseating the EPROM was a good move. Sockets get dirty. Bad connections cause a myriad of problems. Look at the schematics and Service Manual.

Thanks, I have spent a lot of time looking at the service manual before I even posted here. That is how I know about the EGM and OPS2 chips.

Most of the Yamaha FM products have a huge similarity and some of the Service Manuals are very helpful, others less so.

Thanks, I agree.

The DX7II is a close relative of the TX802. I have spent a lot of time reading its service manual too. In spite of them having the same sound generator ICs, the architectures of the two are different. In the DX7II the primary CPU drives the EGM/OPS2 and the secondary CPU handles keyboard inputs etc. In the TX802, the secondary CPU drives the EGM/OPS. This makes the flow of data quite different. You can clearly see this if you compare the block diagrams in the respective service manuals.

The DX7/DX9 service manual has some high level information about the EGS and OPS sound generator IC's. The IC's in the TX802/DX7II are different however. For example, the old EGS has an 8 bit input address bus. The new EGM has only a 5 bit address bus. We have to guess what the inputs to the EGM exactly are.

The weird thing is that the EGM is getting input data that is mostly correct (amplitude envelope rates are correct, amplitude L4 is correct, pitch EG works correctly) and only incorrect in some places: the output level and L1/L2/L3 of the operator amplitude envelopes.

I see no evidence on my scope that they are broken, but I think I will try replacing the RAM chip of the secondary CPU and the 74HC138 address decoder that enables the EGM and OPS2 IC's. If I can get hold of the bin files I will also replace the ROMs because it's easy to do.

Jacob


Re: TX802 troubleshooting

 

Hi Grant,


Op za 4 feb. 2023 om 14:54 schreef grantpbt <grantbt@...>:

Two things to avoid: dismissing input from Daniel Forro and making
assumptions. This is first and foremost electronic troubleshooting.
I am not dismissing Daniel's input, I am reacting to his suggestions.
I really appreciate that Daniel refers to actual problems that others
have had with the TX802, such as the output muting transistors.

Check all the Power Supply voltages. I have seen an increasing number of
Yamaha PSU failures which are happening because a LOT of the Yamaha
designs use a Switch Mode PS. I have been able to repair some of the
PSUs, but not all. There are many threads online discussing this or that
synth or effects unit needing PSU repairs and various successes and
failures.
Logical analysis clearly shows that the problem is in the digital
domain. Everything from the EGM chip on down functions correctly. So
the only power line that matters here is the 5V digital supply. I have
checked that, with an oscilloscope, and it looks fine.

Take a look at the block diagram of the TX802 on page 4/5 of the
service manual. Everything from the EGM on down is working correctly.
That also implies that the "master oscillator" works correctly: if it
didn't, you would never get clean sine waves (at the correct pitch!)
out of the outputs.

If you look on the left of the block diagram you see that the "master
MPU" runs on its own clock crystal. It is responsible for receiving
MIDI. If that clock was not running, or not running at the right rate,
incoming MIDI data would be garbled. MIDI works fine so I know that
clock crystal is fine.

I am not pro-cap replacement, but as far as the PSU is concerned this is
a common problem with them.
I agree. But this just doesn't look like a PSU problem. Remember that
the main CPU works fine. The synth responds to MIDI, I can use all the
buttons in the interface, the display works, there is no garbled text
in it. It does not crash.

The BIN files are everywhere.
I wish that were true. I have spent a lot of time looking already. The
only source I can find for the BIN files is
, where you have
to pay $10 a pop.

Do you know where to find them? The ROMs are called XB223, XB224 and XB536.

I agree that a byte for byte comparison is the right thing to do but I
only have those checksums. And unfortunately, that page does not have
the checksums for TX802 v1.2, which is what I have.


Reseating the EPROM was a good move. Sockets get dirty. Bad connections
cause a myriad of problems. Look at the schematics and Service Manual.
Thanks, I have spent a lot of time looking at the service manual
before I even posted here. That is how I know about the EGM and OPS2
chips.

Most of the Yamaha FM products have a huge similarity and some of the
Service Manuals are very helpful, others less so.
Thanks, I agree.

The DX7II is a close relative of the TX802. I have spent a lot of time
reading its service manual too. In spite of them having the same sound
generator ICs, the architectures of the two are different. In the
DX7II the primary CPU drives the EGM/OPS2 and the secondary CPU
handles keyboard inputs etc. In the TX802, the secondary CPU drives
the EGM/OPS. This makes the flow of data quite different. You can
clearly see this if you compare the block diagrams in the respective
service manuals.

The DX7/DX9 service manual has some high level information about the
EGS and OPS sound generator IC's. The IC's in the TX802/DX7II are
different however. For example, the old EGS has an 8 bit input address
bus. The new EGM has only a 5 bit address bus. We have to guess what
the inputs to the EGM exactly are.

The weird thing is that the EGM is getting input data that is mostly
correct (amplitude envelope rates are correct, amplitude L4 is
correct, pitch EG works correctly) and only incorrect in some places:
the output level and L1/L2/L3 of the operator amplitude envelopes.

I see no evidence on my scope that they are broken, but I think I will
try replacing the RAM chip of the secondary CPU and the 74HC138
address decoder that enables the EGM and OPS2 IC's. If I can get hold
of the bin files I will also replace the ROMs because it's easy to do.

Jacob


Re: TX802 troubleshooting

 

Two things to avoid: dismissing input from Daniel Forro and making assumptions. This is first and foremost electronic troubleshooting.

Check all the Power Supply voltages. I have seen an increasing number of Yamaha PSU failures which are happening because a LOT of the Yamaha designs use a Switch Mode PS. I have been able to repair some of the PSUs, but not all. There are many threads online discussing this or that synth or effects unit needing PSU repairs and various successes and failures.

Look at the waveforms being discussed here with a scope. Don't have these tools? Why not? a decent DMM can be had for less than $100. A brand new excellent scope for under $400. At some point one realizes they don't have the knowledge, skills or tools. This is fine for learning, but don't expect infinite patience from online help.

I am not pro-cap replacement, but as far as the PSU is concerned this is a common problem with them. Definitely check the OS checksum, even better would be a CRC or a direct BIN file comparison.? The BIN files are everywhere.

Reseating the EPROM was a good move. Sockets get dirty. Bad connections cause a myriad of problems. Look at the schematics and Service Manual. Most of the Yamaha FM products have a huge similarity and some of the Service Manuals are very helpful, others less so.

On 2/4/2023 1:24 AM, contact@... wrote:
Op za 4 feb. 2023 om 03:44 schreef Daniel Forro <danforcz@...>:
Have your tried to replace OS Eproms?
I have re-seated them, if that is what you mean. I have an EPROM
reader so I could read their contents and compare the checksums with
those listed on .
I don't find it a promising direction though. If an EPROM was
corrupted there would be crashes, or more other things that go wrong.


Have you done diagnostics test?
Yes.


There were some reports about noise at the outputs in some series of TX802 - solved by replacing opamps.
As I mentioned in my first post, if I take an init patch and change
the algorithm to 32 then I get a perfectly clean sound. That rules out
any problems in the output stages.

Problems with sound quality can be also caused by muting transistors. Somebody deactivated them or pull out, somebody replaced them.
If the muting transistors were bad they would be bad all the time.
They don't know what FM algorithm I'm using.


Check the signal from the output to DAC, to find if the problem is in analog circuit or digital circuit.
As I wrote above, I already know the DAC is fine. It would not be able
to produce clean sine waves with algorithm 32 if it was broken.


Check all crystals, too.
If the crystals were misbehaving many other things would be wrong.
MIDI reception would be messed up. There would be weird sound
artifacts on the outputs. The outputs can produce clean sine waves
with algorithm 32 and the crystals don't know about the algorithm.


Re: TX802 troubleshooting

 

Op za 4 feb. 2023 om 03:44 schreef Daniel Forro <danforcz@...>:
Have your tried to replace OS Eproms?
I have re-seated them, if that is what you mean. I have an EPROM
reader so I could read their contents and compare the checksums with
those listed on .
I don't find it a promising direction though. If an EPROM was
corrupted there would be crashes, or more other things that go wrong.


Have you done diagnostics test?
Yes.


There were some reports about noise at the outputs in some series of TX802 - solved by replacing opamps.
As I mentioned in my first post, if I take an init patch and change
the algorithm to 32 then I get a perfectly clean sound. That rules out
any problems in the output stages.

Problems with sound quality can be also caused by muting transistors. Somebody deactivated them or pull out, somebody replaced them.
If the muting transistors were bad they would be bad all the time.
They don't know what FM algorithm I'm using.


Check the signal from the output to DAC, to find if the problem is in analog circuit or digital circuit.
As I wrote above, I already know the DAC is fine. It would not be able
to produce clean sine waves with algorithm 32 if it was broken.


Check all crystals, too.
If the crystals were misbehaving many other things would be wrong.
MIDI reception would be messed up. There would be weird sound
artifacts on the outputs. The outputs can produce clean sine waves
with algorithm 32 and the crystals don't know about the algorithm.


Re: TX802 troubleshooting

 

Op za 4 feb. 2023 om 03:39 schreef Daniel Forró via groups.io
<danforcz@...>:
It is not recommended to replace all caps, only the bad ones. Service experts say: If it works, leave it so.
I'm with Daniel on this. I have no trouble replacing capacitors myself
but I don't want to solder and desolder on the board without good
reason.

There are no tantalum capacitors in the TX802. Because it's mostly
digital there are also very few electrolytics. There is no point in me
replacing DC blocking capacitors on the headphone output if there is a
problem in the digital domain. There is one capacitor next to the EGM
which I've already replaced with no result.


Re: TX802 troubleshooting

 

Op za 4 feb. 2023 om 05:12 schreef raj juggapah <rajdata01@...>:
I have a DX 7 initial version
Could we move this discussion to its own thread? It has nothing to do
with the TX802 problem this thread started with


Re: TX802 troubleshooting

 

Hi Brian

Good to hear fron you as well

For sure am with you and the group as this keyboard is here to stay for the next century for sure !!

I will send the display messages

Thanks for your support

With kind regards
Raj

On Saturday, February 4, 2023, 08:27:43 AM GMT+4, Brian <briantolson@...> wrote:


I was about to say the same thing almost .. more information please Raj, what do you have on the display for a start?

?

Good to hear you’re still with the group Daniel, funny, I was just thinking about you this morning and wondering what had happened to the DX group.

This was before I saw the original post about the TX802

?

Regards,

Brian.

?

?

From: Daniel Forró via groups.io
Sent: Saturday, 4 February 2023 3:21 PM
To: [email protected]; rajdata01@...
Subject: Re: [YamahaDX] TX802 troubleshooting

?

It can be anything, your description is not enough to do proper diagnostics.

?

Is it totally dead, no display?

?

Start with checking fuses, PSU voltages, replacing bad electrolytic caps in PSU, replacing battery, cleaning and reseating all connectors and IC’s in sockets.

?

When you get some display, do diagnostics test, load patch data and play.

?

Later you can consider replacing OS Eprom for the latest one.

?

Daniel Forro

?



On Feb 4, 2023, at 13:10, raj juggapah via <rajdata01@...> wrote:

?

Dear All

?

Help please !!!

?

I have a DX 7 initial version

?

Problem ...No sound generated at all ....is it a battery change that is required or else

?

Please extend your help .

Many Thanks

?

With kind regards,

Raj

From Mauritius

?

?

?

On Saturday, February 4, 2023, 02:15:04 AM GMT+4, <contact@...> wrote:

?

?

Nothing gets changed in the patch. This is not like a memory corruption problem.

What is happening is that what the display says does not match the
sound the machine makes. For example, the display says all output
levels are zero except OP1 with 99. I can save this just fine, that is
not the problem. The sound that comes out the machine is just not what
the display says.

The main CPU is responsible for editing and patch storage. The
secondary ("slave") CPU is responsible for sending the currently
playing sounds into the EGM, and the algorithm into the OPS2. This is
where the problem must be.

Using a software MIDI editor tells me nothing about what goes on with
the EGM. The MIDI editor can only talk to the main CPU and the main
CPU thinks everything is fine.

I suspect that the output levels and the L1, L2 and L3 levels are
combined because changing L1, L2 and L3 does nothing, just like
changing output levels do nothing

Changing L4 does work; if I set it to 99 on a carrier I get the drone
sound you would expect.

The other thing that _does_ work is setting envelope rates. If I take
an init patch and set R1 of OP2 and OP3 to 0, then I get the proper
sound (single operator sine wave).

My best guess is still that some but not all of the 32 bytes that go
into the EGM get corrupted. And it's always the same bytes that get
corrupted.

Op vr 3 feb. 2023 om 21:45 schreef belzrebuth s via
<belzrebuth=[email protected]>:


>
> I would troubleshoot with a midi editor like SoundQuest or whatever to see exactly what gets changed realtime.
>
> With an init patch you may be missing something.
>
> If you get the other operator levels back to zero do they stay at zero after saving?
>
> Can you make a patch? from scratch set levels back to zero and then set them like 10 20 30 then save and recall that patch?
>
> If you're able to recall that patch I would compare the original and the modified one (modified by the machine I mean) to verify my findings.
>
> If it's indeed *only* the OP output levels that get scrambled only then I would proceed further chasing that error.
>
> In fact one could take it even further and take a screenshot of a patch with ALL values set in a custom way and check what else gets changed before going into a single direction.
>
> On 2/3/2023 10:31 PM, José Juan wrote:
>
> Hi,
>
> I did a full recap of the TX802, and it sounded awesome afterwards.
>
> Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.
>
> To change all capacitors is a PITA, but the machine gets new expected life.
>
> Just my suggest. Not every tech guy is capable of doing that without damaging the unit.
>
> Good luck, and take care.
>
> JJ
>
> El vie, 3 feb 2023, 21:24, <contact@...> escribió:
>>
>> Hello group,
>>
>> I would like to share a troubleshooting story I am in the middle of.
>>
>> I bought a broken TX802 on the internet. I knew it was broken when I bought it, I felt like taking a chance. The seller said it worked but has "digital noise".
>>
>> It turns out this TX802 is in pretty good shape. Everything works except that the sounds are wrong. There appears to be something wrong with the output levels of the operators.
>>
>> If I make an init sound, I am supposed to get a single operator sine wave with an organ envelope. The user interface shows the expected parameters. But when I play it, I get more or less the sound of algorithm 1 with all operators at 99. A harsh overmodulated FM sound. When I then change the algorithm to 32, I get a clean sine wave sound.
>>
>> It's a fascinating puzzle for me. Almost all the explanations I can come up with would make the TX sound more broken than it actually does. The EGM and OPS2 chips cannot be broken because they can make clean sounds. (I have a DX7II which is my reference.) Data is getting corrupted only in a very specific place, which happens to affect the output levels.
>>
>> My best guess at the moment is that there is a problem with the chip enable line of the EGM chip that causes it to latch bad output level data when it should not be reading data in the first place. But I have not seen evidence of that yet on my oscilloscope.
>>
>> I don't know if anyone else finds this interesting, but if there is someone who finds it interesting, they are probably on this list. :)
>>
>> Cheers, Jacob
>>
>>
>>
>>
>
>
>
>
>
>





?

?





Re: TX802 troubleshooting

 

Many Thanks Daniel

Hints are perfect

Display

When I select cartridge ...it says.........not ready which is fine as I did not insert the cartridge.

Back on normal it says something which i will share with you and possible you can furher direcgt me

Many Thanks again Bro

With kind regards
Raj

On Saturday, February 4, 2023, 08:21:59 AM GMT+4, Daniel Forró via groups.io <danforcz@...> wrote:


It can be anything, your description is not enough to do proper diagnostics.

Is it totally dead, no display?

Start with checking fuses, PSU voltages, replacing bad electrolytic caps in PSU, replacing battery, cleaning and reseating all connectors and IC’s in sockets.

When you get some display, do diagnostics test, load patch data and play.

Later you can consider replacing OS Eprom for the latest one.

Daniel Forro


On Feb 4, 2023, at 13:10, raj juggapah via <rajdata01@...> wrote:

Dear All

Help please !!!

I have a DX 7 initial version

Problem ...No sound generated at all ....is it a battery change that is required or else

Please extend your help .
Many Thanks

With kind regards,
Raj
From Mauritius



On Saturday, February 4, 2023, 02:15:04 AM GMT+4, <contact@...> wrote:


Nothing gets changed in the patch. This is not like a memory corruption problem.

What is happening is that what the display says does not match the
sound the machine makes. For example, the display says all output
levels are zero except OP1 with 99. I can save this just fine, that is
not the problem. The sound that comes out the machine is just not what
the display says.

The main CPU is responsible for editing and patch storage. The
secondary ("slave") CPU is responsible for sending the currently
playing sounds into the EGM, and the algorithm into the OPS2. This is
where the problem must be.

Using a software MIDI editor tells me nothing about what goes on with
the EGM. The MIDI editor can only talk to the main CPU and the main
CPU thinks everything is fine.

I suspect that the output levels and the L1, L2 and L3 levels are
combined because changing L1, L2 and L3 does nothing, just like
changing output levels do nothing

Changing L4 does work; if I set it to 99 on a carrier I get the drone
sound you would expect.

The other thing that _does_ work is setting envelope rates. If I take
an init patch and set R1 of OP2 and OP3 to 0, then I get the proper
sound (single operator sine wave).

My best guess is still that some but not all of the 32 bytes that go
into the EGM get corrupted. And it's always the same bytes that get
corrupted.

Op vr 3 feb. 2023 om 21:45 schreef belzrebuth s via
<belzrebuth=[email protected]>:

>
> I would troubleshoot with a midi editor like SoundQuest or whatever to see exactly what gets changed realtime.
>
> With an init patch you may be missing something.
>
> If you get the other operator levels back to zero do they stay at zero after saving?
>
> Can you make a patch? from scratch set levels back to zero and then set them like 10 20 30 then save and recall that patch?
>
> If you're able to recall that patch I would compare the original and the modified one (modified by the machine I mean) to verify my findings.
>
> If it's indeed *only* the OP output levels that get scrambled only then I would proceed further chasing that error.
>
> In fact one could take it even further and take a screenshot of a patch with ALL values set in a custom way and check what else gets changed before going into a single direction.
>
> On 2/3/2023 10:31 PM, José Juan wrote:
>
> Hi,
>
> I did a full recap of the TX802, and it sounded awesome afterwards.
>
> Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.
>
> To change all capacitors is a PITA, but the machine gets new expected life.
>
> Just my suggest. Not every tech guy is capable of doing that without damaging the unit.
>
> Good luck, and take care.
>
> JJ
>
> El vie, 3 feb 2023, 21:24, <contact@...> escribió:
>>
>> Hello group,
>>
>> I would like to share a troubleshooting story I am in the middle of.
>>
>> I bought a broken TX802 on the internet. I knew it was broken when I bought it, I felt like taking a chance. The seller said it worked but has "digital noise".
>>
>> It turns out this TX802 is in pretty good shape. Everything works except that the sounds are wrong. There appears to be something wrong with the output levels of the operators.
>>
>> If I make an init sound, I am supposed to get a single operator sine wave with an organ envelope. The user interface shows the expected parameters. But when I play it, I get more or less the sound of algorithm 1 with all operators at 99. A harsh overmodulated FM sound. When I then change the algorithm to 32, I get a clean sine wave sound.
>>
>> It's a fascinating puzzle for me. Almost all the explanations I can come up with would make the TX sound more broken than it actually does. The EGM and OPS2 chips cannot be broken because they can make clean sounds. (I have a DX7II which is my reference.) Data is getting corrupted only in a very specific place, which happens to affect the output levels.
>>
>> My best guess at the moment is that there is a problem with the chip enable line of the EGM chip that causes it to latch bad output level data when it should not be reading data in the first place. But I have not seen evidence of that yet on my oscilloscope.
>>
>> I don't know if anyone else finds this interesting, but if there is someone who finds it interesting, they are probably on this list. :)
>>
>> Cheers, Jacob
>>
>>
>>
>>
>
>
>
>
>
>











Re: TX802 troubleshooting

 

开云体育

I was about to say the same thing almost .. more information please Raj, what do you have on the display for a start?

?

Good to hear you’re still with the group Daniel, funny, I was just thinking about you this morning and wondering what had happened to the DX group.

This was before I saw the original post about the TX802

?

Regards,

Brian.

?

?

From: Daniel Forró via groups.io
Sent: Saturday, 4 February 2023 3:21 PM
To: [email protected]; rajdata01@...
Subject: Re: [YamahaDX] TX802 troubleshooting

?

It can be anything, your description is not enough to do proper diagnostics.

?

Is it totally dead, no display?

?

Start with checking fuses, PSU voltages, replacing bad electrolytic caps in PSU, replacing battery, cleaning and reseating all connectors and IC’s in sockets.

?

When you get some display, do diagnostics test, load patch data and play.

?

Later you can consider replacing OS Eprom for the latest one.

?

Daniel Forro

?



On Feb 4, 2023, at 13:10, raj juggapah via <rajdata01@...> wrote:

?

Dear All

?

Help please !!!

?

I have a DX 7 initial version

?

Problem ...No sound generated at all ....is it a battery change that is required or else

?

Please extend your help .

Many Thanks

?

With kind regards,

Raj

From Mauritius

?

?

?

On Saturday, February 4, 2023, 02:15:04 AM GMT+4, <contact@...> wrote:

?

?

Nothing gets changed in the patch. This is not like a memory corruption problem.

What is happening is that what the display says does not match the
sound the machine makes. For example, the display says all output
levels are zero except OP1 with 99. I can save this just fine, that is
not the problem. The sound that comes out the machine is just not what
the display says.

The main CPU is responsible for editing and patch storage. The
secondary ("slave") CPU is responsible for sending the currently
playing sounds into the EGM, and the algorithm into the OPS2. This is
where the problem must be.

Using a software MIDI editor tells me nothing about what goes on with
the EGM. The MIDI editor can only talk to the main CPU and the main
CPU thinks everything is fine.

I suspect that the output levels and the L1, L2 and L3 levels are
combined because changing L1, L2 and L3 does nothing, just like
changing output levels do nothing

Changing L4 does work; if I set it to 99 on a carrier I get the drone
sound you would expect.

The other thing that _does_ work is setting envelope rates. If I take
an init patch and set R1 of OP2 and OP3 to 0, then I get the proper
sound (single operator sine wave).

My best guess is still that some but not all of the 32 bytes that go
into the EGM get corrupted. And it's always the same bytes that get
corrupted.

Op vr 3 feb. 2023 om 21:45 schreef belzrebuth s via
<belzrebuth=[email protected]>:


>
> I would troubleshoot with a midi editor like SoundQuest or whatever to see exactly what gets changed realtime.
>
> With an init patch you may be missing something.
>
> If you get the other operator levels back to zero do they stay at zero after saving?
>
> Can you make a patch? from scratch set levels back to zero and then set them like 10 20 30 then save and recall that patch?
>
> If you're able to recall that patch I would compare the original and the modified one (modified by the machine I mean) to verify my findings.
>
> If it's indeed *only* the OP output levels that get scrambled only then I would proceed further chasing that error.
>
> In fact one could take it even further and take a screenshot of a patch with ALL values set in a custom way and check what else gets changed before going into a single direction.
>
> On 2/3/2023 10:31 PM, José Juan wrote:
>
> Hi,
>
> I did a full recap of the TX802, and it sounded awesome afterwards.
>
> Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.
>
> To change all capacitors is a PITA, but the machine gets new expected life.
>
> Just my suggest. Not every tech guy is capable of doing that without damaging the unit.
>
> Good luck, and take care.
>
> JJ
>
> El vie, 3 feb 2023, 21:24, <contact@...> escribió:
>>
>> Hello group,
>>
>> I would like to share a troubleshooting story I am in the middle of.
>>
>> I bought a broken TX802 on the internet. I knew it was broken when I bought it, I felt like taking a chance. The seller said it worked but has "digital noise".
>>
>> It turns out this TX802 is in pretty good shape. Everything works except that the sounds are wrong. There appears to be something wrong with the output levels of the operators.
>>
>> If I make an init sound, I am supposed to get a single operator sine wave with an organ envelope. The user interface shows the expected parameters. But when I play it, I get more or less the sound of algorithm 1 with all operators at 99. A harsh overmodulated FM sound. When I then change the algorithm to 32, I get a clean sine wave sound.
>>
>> It's a fascinating puzzle for me. Almost all the explanations I can come up with would make the TX sound more broken than it actually does. The EGM and OPS2 chips cannot be broken because they can make clean sounds. (I have a DX7II which is my reference.) Data is getting corrupted only in a very specific place, which happens to affect the output levels.
>>
>> My best guess at the moment is that there is a problem with the chip enable line of the EGM chip that causes it to latch bad output level data when it should not be reading data in the first place. But I have not seen evidence of that yet on my oscilloscope.
>>
>> I don't know if anyone else finds this interesting, but if there is someone who finds it interesting, they are probably on this list. :)
>>
>> Cheers, Jacob
>>
>>
>>
>>
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Re: TX802 troubleshooting

 

开云体育

It can be anything, your description is not enough to do proper diagnostics.

Is it totally dead, no display?

Start with checking fuses, PSU voltages, replacing bad electrolytic caps in PSU, replacing battery, cleaning and reseating all connectors and IC’s in sockets.

When you get some display, do diagnostics test, load patch data and play.

Later you can consider replacing OS Eprom for the latest one.

Daniel Forro


On Feb 4, 2023, at 13:10, raj juggapah via <rajdata01@...> wrote:

Dear All

Help please !!!

I have a DX 7 initial version

Problem ...No sound generated at all ....is it a battery change that is required or else

Please extend your help .
Many Thanks

With kind regards,
Raj
From Mauritius



On Saturday, February 4, 2023, 02:15:04 AM GMT+4, <contact@...> wrote:


Nothing gets changed in the patch. This is not like a memory corruption problem.

What is happening is that what the display says does not match the
sound the machine makes. For example, the display says all output
levels are zero except OP1 with 99. I can save this just fine, that is
not the problem. The sound that comes out the machine is just not what
the display says.

The main CPU is responsible for editing and patch storage. The
secondary ("slave") CPU is responsible for sending the currently
playing sounds into the EGM, and the algorithm into the OPS2. This is
where the problem must be.

Using a software MIDI editor tells me nothing about what goes on with
the EGM. The MIDI editor can only talk to the main CPU and the main
CPU thinks everything is fine.

I suspect that the output levels and the L1, L2 and L3 levels are
combined because changing L1, L2 and L3 does nothing, just like
changing output levels do nothing

Changing L4 does work; if I set it to 99 on a carrier I get the drone
sound you would expect.

The other thing that _does_ work is setting envelope rates. If I take
an init patch and set R1 of OP2 and OP3 to 0, then I get the proper
sound (single operator sine wave).

My best guess is still that some but not all of the 32 bytes that go
into the EGM get corrupted. And it's always the same bytes that get
corrupted.

Op vr 3 feb. 2023 om 21:45 schreef belzrebuth s via
<belzrebuth=[email protected]>:

>
> I would troubleshoot with a midi editor like SoundQuest or whatever to see exactly what gets changed realtime.
>
> With an init patch you may be missing something.
>
> If you get the other operator levels back to zero do they stay at zero after saving?
>
> Can you make a patch? from scratch set levels back to zero and then set them like 10 20 30 then save and recall that patch?
>
> If you're able to recall that patch I would compare the original and the modified one (modified by the machine I mean) to verify my findings.
>
> If it's indeed *only* the OP output levels that get scrambled only then I would proceed further chasing that error.
>
> In fact one could take it even further and take a screenshot of a patch with ALL values set in a custom way and check what else gets changed before going into a single direction.
>
> On 2/3/2023 10:31 PM, José Juan wrote:
>
> Hi,
>
> I did a full recap of the TX802, and it sounded awesome afterwards.
>
> Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.
>
> To change all capacitors is a PITA, but the machine gets new expected life.
>
> Just my suggest. Not every tech guy is capable of doing that without damaging the unit.
>
> Good luck, and take care.
>
> JJ
>
> El vie, 3 feb 2023, 21:24, <contact@...> escribió:
>>
>> Hello group,
>>
>> I would like to share a troubleshooting story I am in the middle of.
>>
>> I bought a broken TX802 on the internet. I knew it was broken when I bought it, I felt like taking a chance. The seller said it worked but has "digital noise".
>>
>> It turns out this TX802 is in pretty good shape. Everything works except that the sounds are wrong. There appears to be something wrong with the output levels of the operators.
>>
>> If I make an init sound, I am supposed to get a single operator sine wave with an organ envelope. The user interface shows the expected parameters. But when I play it, I get more or less the sound of algorithm 1 with all operators at 99. A harsh overmodulated FM sound. When I then change the algorithm to 32, I get a clean sine wave sound.
>>
>> It's a fascinating puzzle for me. Almost all the explanations I can come up with would make the TX sound more broken than it actually does. The EGM and OPS2 chips cannot be broken because they can make clean sounds. (I have a DX7II which is my reference.) Data is getting corrupted only in a very specific place, which happens to affect the output levels.
>>
>> My best guess at the moment is that there is a problem with the chip enable line of the EGM chip that causes it to latch bad output level data when it should not be reading data in the first place. But I have not seen evidence of that yet on my oscilloscope.
>>
>> I don't know if anyone else finds this interesting, but if there is someone who finds it interesting, they are probably on this list. :)
>>
>> Cheers, Jacob
>>
>>
>>
>>
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>
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>
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