Be prepared for more requests David, several other pages are missing as well ;=).
Albert

I'll email it directly in two seconds, since attachments tend to be dropped
from the mailing list.

I just scanned the two pages into one tif file. Chopping it up is left as
an exercise for the reader. ;-)

If someone else wants a copy let me know, I can mail it..

David

------------------------------------

Yahoo! Groups Links

?

Hi Herbert,

I assumed that myself.

The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?

The manuals, both the op and service, say on page 1-7 and 1-3 respectively:

"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."

Bet never gets back to the topic, WITH the memory back-up applied.

Any thoughts?

Best regards,

Bogdan

--- In TekScopes@..., "Herbert" wrote:
>
> Hi Bogdan,
>
> it is normal for the HM62256B to keep the data down to approx. 1V.
> I think what zou see is, that the system does not recognnize the power off phase .
>
> Herbert
>
>
> --- In TekScopes@..., "bogroca" wrote:
> >
> > Hi all,
> >
> > After replacing the ROMs (document to come soon), I got on to the RAM.
> >
> > Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
> >
> > First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
> >
> > ...It booted directly in the "stored" mode with the right wave displayed.
> >
> > I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
> >
> > One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
> >
> > Sorry for the long post and thank you inadvance!
> >
> > Bogdan
> >
>

Hi Bogdan,

it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .

Herbert


--- In TekScopes@..., "bogroca" wrote:

Hi all,

After replacing the ROMs (document to come soon), I got on to the RAM.

Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.

First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...

...It booted directly in the "stored" mode with the right wave displayed.

I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.

One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.

Sorry for the long post and thank you inadvance!

Bogdan

?

Hi all out there,

in all the manual copies of the "Using the Waveform Calculator - 7854" available on the web the pages 6-22 and 6-23 are missing.
Does somebody have a paper version and can scan those two pages ???
I would than correct the manual and provide it to the manuals respositories in the web !

Thanks in advance

Herbert

I'll email it directly in two seconds, since attachments tend to be dropped
from the mailing list.

I just scanned the two pages into one tif file. Chopping it up is left as
an exercise for the reader. ;-)

If someone else wants a copy let me know, I can mail it..

David

?

6-21 contains the section "Observing the waveform memories at power-up" ?

If so, I've a dead tree copy I can scan.....

On Mon, Jan 21, 2013 at 7:28 AM, Herbert measurement@...> wrote:
> Hi all out there,
>
> in all the manual copies of the "Using the Waveform Calculator - 7854" available on the web the pages 6-22 and 6-23 are missing.
> Does somebody have a paper version and can scan those two pages ???
> I would than correct the manual and provide it to the manuals respositories in the web !
>
> Thanks in advance
>
> Herbert
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>

Hi all out there,

in all the manual copies of the "Using the Waveform Calculator - 7854" available on the web the pages 6-22 and 6-23 are missing.
Does somebody have a paper version and can scan those two pages ???
I would than correct the manual and provide it to the manuals respositories in the web !

Thanks in advance

Herbert




------------------------------------

Yahoo! Groups Links

Hi all,

After replacing the ROMs (document to come soon), I got on to the RAM.

Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.

First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...

...It booted directly in the "stored" mode with the right wave displayed.

I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.

One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.

Sorry for the long post and thank you inadvance!

Bogdan

It may fix some of the U800s that have failed:



Please search this forum:

"U800 baking"

This has been discussed ad nauseam.

--Victor

--- In TekScopes@... <mailto:TekScopes%40yahoogroups.com>, Jeff Machesky wrote:

Removing the heat from the plastic should in turn drop the temperature
of the metal fin some. Now does that produce undesirable thermal

shifts,

no idea. In my case I'm pulling heat from a little of both, but mostly
the plastic.

So what does baking the chip actually fix? I know some IC's are
sensitive to humidity, but this is usually only just before the high
temperature of a reflow oven. The trapped moisture can cause defects
when heated.

Jeff

On 1/20/2013 6:07 PM, Dave C wrote:

Last time 'round on this topic I designed a heatsink that contacts
only the metal tab parts of U800, not the plastic body. This is the
intended (I think) means of getting the heat out of the chip.

The drawing of this heatsink is in the Tekscopes files page on the
Yahoo Groups web site. Look for a folder titled "U800". Its in there.

Dave

-=-=-=-

On 20 January 2013, at 2:05 PM, Jeff Machesky wrote:

Is all of this heat related? One of the first things I did when

getting

my 2465BDM was strap a very large heat sink to the U800 chip

with good

quality thermal compound and very secure mounting. It's larger

then the

chip. It runs just over room temperature with the case on. I

measured it

with a type K probe through the vents and touching the middle of the
heat sink with a dab of thermal compound over a half hour or so

time

frame.

I do notice mine drifts a tiny tiny bit on warm up, one or two

mm to

the

left. It later snaps back about 1mm to the right.

Jeff

Has someone actually counterfeited 2N3904s? How desperate did they
have to be?

On Sun, 20 Jan 2013 17:19:02 -0800 (PST), Jim wrote:

I hope they're not counterfeit ....

You should test a few to see where Ft seems to be.

73
Jim N6ITQ?

---

From: David
To: TekScopes@...
Sent: Sunday, January 20, 2013 7:24 PM
Subject: Re: [TekScopes] Re: Type 184 Time Mark Generator Transistor Question

Has someone actually counterfeited 2N3904s?? How desperate did they
have to be?

On Sun, 20 Jan 2013 17:19:02 -0800 (PST), Jim <n6otq@...> wrote:

>I hope they're not counterfeit ....
>
>You should test a few to see where Ft seems to be.
>
>73
>Jim N6ITQ?


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? ?

Removing the heat from the plastic should in turn drop the temperature
of the metal fin some. Now does that produce undesirable thermal shifts,
no idea. In my case I'm pulling heat from a little of both, but mostly
the plastic.

So what does baking the chip actually fix? I know some IC's are
sensitive to humidity, but this is usually only just before the high
temperature of a reflow oven. The trapped moisture can cause defects
when heated.

Jeff

On 1/20/2013 6:07 PM, Dave C wrote:

Last time 'round on this topic I designed a heatsink that contacts
only the metal tab parts of U800, not the plastic body. This is the
intended (I think) means of getting the heat out of the chip.

The drawing of this heatsink is in the Tekscopes files page on the
Yahoo Groups web site. Look for a folder titled "U800". Its in there.

Dave

-=-=-=-

On 20 January 2013, at 2:05 PM, Jeff Machesky wrote:

Is all of this heat related? One of the first things I did when getting
my 2465BDM was strap a very large heat sink to the U800 chip with good
quality thermal compound and very secure mounting. It's larger then the
chip. It runs just over room temperature with the case on. I

measured it

with a type K probe through the vents and touching the middle of the
heat sink with a dab of thermal compound over a half hour or so time

frame.

I do notice mine drifts a tiny tiny bit on warm up, one or two mm to

the

left. It later snaps back about 1mm to the right.

Jeff

I hope they're not counterfeit ....

You should test a few to see where Ft seems to be.

73
Jim N6ITQ

---

From: "andersen_bill@..."
To: TekScopes@...
Sent: Sunday, January 20, 2013 7:04 PM
Subject: [TekScopes] Re: Type 184 Time Mark Generator Transistor Question

Well, I just ordered a bag of 100 2N3904's for $4.

Hopefully all goes well

B
--- In TekScopes@..., "andersen_bill@..."? wrote:
>
> I am repairing a 184 that has had transistors removed from the countdown board.
>
> I am looking at;
>
> Q104
>
> Q114
>
> Q134
>
> SM says "selected from 2N3251"
>
> I can get 2N3251A's local.
>
> I looked at the data sheets. Specs are close. Looks like the A has higher ratings.
>
> Does anyone know if they will work or do I need the non A part?
>
> TIA
>
> B
>




------------------------------------

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