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Ron,
Ok now try to clear 04 diagnostic with
EXER 3 as described in other post I sent. Calibration may need to be done if values aren’t correct.

Craig, all pinouts of U2101 have intact connection to the next component and the resistor ladder resistors ohm correctly including connection to +10V Ref. The C2010 measures 15.8 ?F.

pac085, I received an Amazon XGPro T48. Doesn’t seem to work at all. Version 12.75 software reads everything FF, says it PROG’s - nothing written. v12.85 software only gives programmer not connected. Not a fan.

I copied the Qservice startup .bin file and did start up; it’s a little different result. I still have a Test 04 error, but when cleared with A/B only two trace lines, but no gibberish on readout.

Thx, Ron

Hi all,

I had a breakthrough over the weekend with my balky 492P. Rapping the VR module with a rubber screwdriver handle brought back the missing ~20 dBm of amplitude in fits and starts, so I replaced it with a spare and it seemed fine, working as expected with reference levels.

I was super excited until I started it up the next day and it had crapped out again: on the -20 dBm reference level, a -20 dBm signal is 2-3 divisions down from the top. Sadly, I did not check 110 MHz IF output power while it was working, so have no idea if I was on the right track with that.

Having resurrected (for now) my new HP 5350B counter,[1] I was curious to measure the LO frequencies.

The 1st LO on manual sweep can vary from 1.894 to 6.680 GHz. The service manual says the YIG has a tuning range of 2.072 to 6.35 GHz,[2] so I guess this is okay?

The 2nd LO maxes out at 2178 MHz in band 1. This is an old 492 with the cavity 2nd LO that has a tuning slug in the side, but it cannot be adjusted to 2182 MHz per the service manual.[3] If I disconnect the cable on the +10 dBm output of the 2nd LO, though (which goes to the four-cavity filter of the 2nd converter), the front panel output of the LO is at 2182 MHz as expected.

At this point, my guess is a bad 2nd LO, but apparently the Shaper and Bias board next to it tunes and sweeps(?) the 2nd LO. I left out a cal step of adjusting 1st LO and 2nd LO Sweep,[4] so maybe that warrants a closer look, as I thought the 2nd LO operated at a fixed frequency. None of this explains why it worked for a while on Saturday, though; some temperature dependency is all I can think of.

thanks,
Adam

[1] The counter reads 999.9998 MHz on the 1 ns output on my TG501
[2] page 5-5 of 492P service manual for SN B029999 and below
[3] page 3-45 ibid
[4] page 3-44 ibid

I appreciate it H?kan. Information on the rack mount versions of the 500 series is pretty hard to come by.

I agree, WR probe may not be useful especially if you have a LA. With WR option back case have a BNC for trigger output. It is possible to re-wire it for 10MHz input for better CTT time resolution. Even it may not be that useful if you already have a frequency counter.

Yes, I have a Racal Dana 1998 with higher resolution, high stability option and GPSDO.
I would not bother with messing with option 1E (even if it seems easy to do) if it was just for 8 digit precision/resolution. If it were for the scope timebase it would be another story, but it seems apparently impossible.

In that case Dallas -> FRAM change is not applicable, at least it is not a drop in replacement. Your board has an accessible battery, if you are careful and supply a secondary power source you can change the battery without losing contents. You could even decide to put a battery holder for future replacement.

Yes, but having a battery it's really pissing me off, provided all the mess it causes. It reminds me about Icom IC-751A transceiver (and family), it has the MCU program loaded in SRAM(!), if you lose the battery charge, the radio becomes a paperweight.


Anyway I would like to go from SRAM to FRAM.
If this would not be possible eventually I could change the battery.

Having an EPROM burned would allow me to regenerate values in SRAM if something goes bad during the battery surgery operation.
Temporarily substituting the firmware eprom with this one that has a program and my cal data in it to populate again the SRAM.

I have the BOM, once it will be clear to me that/if my 2465B can support a FRAM I will decide how to proceed.

Giuseppe Marullo
IW2JWW - JN45RQ

That’s awesome, Craig! Greatly appreciated. I was thinking it was U2550 on schematic <1>, like a dope. I’ll run through it later tonight.

Thx, Ron

On Tue, Mar 18, 2025 at 07:00 AM, Giuseppe Marullo[iw2jww] wrote:

I don't have a eeprom programmer but I will buy one if needed.

I'd like to see more discussion about using a Pi, to program the FRAM.
The logic levels... AFAIK.. are compatible.
Could do it in Python.
Why not?
--
Roy Thistle

Ron,
I have added pictures to photo area albums. Review this album.

/g/TekScopes/album?id=301356

Craig

Hi Giueppe,
My comments are below.

On Tue, Mar 18, 2025 at 07:00 AM, Giuseppe Marullo[iw2jww] wrote:

>the 6 pin LEMO connector at the back for WR probe, assuming someone
>didn't swap the boards inside.
I have the connector(not the probe), just I don't know how useful the
probe it could be in today's world. I have a separate DSLogic LA for
digital debugging.

I agree, WR probe may not be useful especially if you have a LA. With WR option back case have a BNC for trigger output. It is possible to re-wire it for 10MHz input for better CTT time resolution. Even it may not be that useful if you already have a frequency counter.

My scope is low serial one, there is no Dallas.

What is not clear to me is if the FRAM mod is suitable for a low serial,
and if eventually I could use the DALLAS on a low serial model.

In that case Dallas -> FRAM change is not applicable, at least it is not a drop in replacement. Your board has an accessible battery, if you are careful and supply a secondary power source you can change the battery without losing contents. You could even decide to put a battery holder for future replacement.

I have dumped the EXT 2 values and I would like to get rid of any
battery if possible but I am open to all the available options, possibly
validated by someone else.

I don't have a eeprom programmer but I will buy one if needed.
Thanks for the help!

With Dallas chip carefully desoldering it keeps the contents and you can read back the data. With your board you can't read the SRAM once it is removed. I don't have any experience with low serial A5 boards and I don't know if others have modifications for battery backed SRAM. I recommend supplying a secondary power source, then carefully removing old battery without shorting supplies and replacing with a new one. Then repeat in another 10-20 years :) I don't think EEPROM programmer will be of much use.

Ozan

Thanks Ozan,

That picture doesn't look like a 2465B. Timebase knob and trigger

area looks different.
So it was indeed a 2465 manual, just not the "B variant". That explains why I was never able to find such a panel on a 2465B on the internet.

You can check if you have CTT and WR by pressing "MEASURE". If you

Yes I have:

have "COUNTER" menu at top right you have CTT. In addition if you

press ><MORE>
Yes I have but you also need to click on CONFIGURE before having it display WR-RADIX:

There is a test mode (Buffer exercise F1) that shows list of options but it doesn't distinguish between CTT vs CTT+WR. Another indicator is

Didn't try that, I am scared I would initiate some CAL routine, even if I double checked that P501 is in NO CAL position. At this point, it seems I do have:
OPTION 5
OPTION 6 + 9
So I won't check further.

the 6 pin LEMO connector at the back for WR probe, assuming someone didn't swap the boards inside.

I have the connector(not the probe), just I don't know how useful the probe it could be in today's world. I have a separate DSLogic LA for digital debugging.

Regarding Dallas NVRAM replacement: I recently removed a 34 year old

My scope is low serial one, there is no Dallas.

What is not clear to me is if the FRAM mod is suitable for a low serial, and if eventually I could use the DALLAS on a low serial model.

I have dumped the EXT 2 values and I would like to get rid of any battery if possible but I am open to all the available options, possibly validated by someone else.

I don't have a eeprom programmer but I will buy one if needed.
Thanks for the help!

Giueppe Marullo
IW2JWW - JN45RQ

On Mon, Mar 17, 2025 at 10:45 AM, Giuseppe Marullo[iw2jww] wrote:

Thanks Alex,
1) could you please confirm that your 2465B has a low serial?

Forgot to mention my scope is above 50K SN.

2) Could you be so kind and send me *exact* Mouse BOM for it?

Here are the links I have on file:
Hope they still work, Mouser's AI is once again blocking me on this browser for being "outdated" and probably not being able to fully track my steps, so could not check them.

Aries 28-650000-10 adapter


DS1225AD-150 NVRAM


FM16W08 FRAM


DIP28 LOW PROFILE SOCKET

I could buy the GQ4X4 + eraser,

You don't need to buy any separate eraser, the programmer can clear the chips when necessary.

pac1085, I copied the original 1991 SRAM data to buffer, then put it on the new SRAM. That generated the 04 Fail. I then put the 1991 SRAM back in the A5, it also failed. The data had been changed on the SRAM in both cases. I rewrote the data back to what it was when the original 1991 SRAM was initially removed, put it in the 2465b and the result was another 04 Fail and another overwrite by the DUT.

I have the .bin data from a Qservice generic “startup” 2465b SRAM. I can certainly try that.

Craig, “Can you just go beyond the error and get a normal display?”

I get 4 CRT lines and gibberish on the bottom of the screen. Can you explain to me where on the schemtic “resistor ladder circuits with your ohm meter ahead of the DAC chip” is?

Thx, Ron

On Mon, Mar 17, 2025 at 06:17 PM, Giuseppe Marullo[iw2jww] wrote:

Yes, but according to the manual,should have a different designation,
not "A/B TRIG" but "A/B MENU", also B TRIG options seems different.

Options manual at

and my 2465B with option 9 (CTT/WR) shows "A/B TRIG"

...
This is an image(awful) of the manual:

That picture doesn't look like a 2465B. Timebase knob and trigger area looks different.

Anyway, I will try to activate the function to see if it works, simply
pressing the A/B Trig won't work, probably I need something connected.

You can check if you have CTT and WR by pressing "MEASURE". If you have "COUNTER" menu at top right you have CTT. In addition if you press <MORE> and see "WR-RADIX" menu you have CTT+word recognizer. If you have any errors during boot up you can clear most of them temporarily by pressing A/B TRIG button.

There is a test mode (Buffer exercise F1) that shows list of options but it doesn't distinguish between CTT vs CTT+WR. Another indicator is the 6 pin LEMO connector at the back for WR probe, assuming someone didn't swap the boards inside.

Regarding Dallas NVRAM replacement: I recently removed a 34 year old Dallas NVRAM from a 2465B, it still showed 3.1V battery voltage. They last quite a bit longer than 10 years. I recommend a low profile precision socket and another Dallas part from a reliable source like Digikey/Mouser. I also did the FRAM change for a scope few years back, it doesn't have low voltage detection so it may get corrupted one day. Recently I added a coincell battery holder to another Dallas chip and I like it better than the FRAM solution.

Ozan

To second that I can add the fact that any crt TV will behave like this: EHT too low will produce "picture too big" whereas EHT loo high will show a reduced picture size. Was very common to deal with through the early 1970s when Philips ctv with PD500 and PD510 EHT regulation triode valves were popular in Europe. Still have some
Joe

Thank you -I obviously had an early download.
This versn is much more helpful, especially as it shows how to put the
bits back together (all those screws !!)
Thanks again.
Tim


On Mon, 17 Mar 2025 at 23:14, Ke-Fong Lin via groups.io <anotherlin=
[email protected]> wrote:

Hi,

The manual doesn't look like the "interim" one:



They've updated the pdf file I guess.
I also have the pdf from Artek, it looks identical.

Best regards,

I guess a simple explanation would be that the higher the accelerating voltage is, the faster the electrons go from the gun to the screen, and spend less time passing the deflection plates, therefore the deflection plates have less influence in changing the direction of the electrons. So the higher the EHT voltage, the lesser the deflection is

<Space>
John

Ron,
Well I have used my GQ4x4 for many years and it works fine for me. But you shouldn't have to keep heating your solder joints if you had quick solder flow on each pin. Seems strange that the original NVRAM that was ok when you unsoldered doesn't work but It could have gotten messed up in the process. Can you just go beyond the error and get a normal display? Review the resistor ladder circuits with your ohm meter ahead of the DAC chip.
I know this may not be helpful, in years past I used to send all my A5’s to QService for repair and probably over 50% of the NVRAM chips he tried to copy he couldn't get data saved, he is very qualified in repair of these modules. But now I do the work myself and I haven't had an issue saving and reprogramming data. But I also replace caps and any other resistors needed to correct ladder circuit. So it’s probably not your programmer.

I remember frying some diodes during lunch on a brand new 575 in a class. Teacher walked by and said what are you doing? I and classmate said burning up some diodes. Good, good, he said, knowing we were learning. Try some sacrificial junctions. Turn up the drive and see huge loops from the heating.

Not sure what you mean regarding the accessory boards/widgets. This is the exact package I bought:
I bought the one with the extras since I wanted them for other things in the future, retro pcs etc, but none of them are needed for this purpose.
You never attempted to write the original Dallas chip right? Just read it once?

Somewhere on eevblog (and maybe in this group) people have posted their bin files, you can restore someone else's 2464B cal data to your new Dallas chip just to validate functionality/rule out the read from your old chip. I've seen posts from other people on forums of their old chips losing their data after being desoldered.

Good luck!!