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Few additional notes about "leaked" EPROMs data recovery.

CMOS chips 27Cxxx allow quite deep lowering of Vcc, some to almost 3.3V level, and sometimes incompletely erased chips that tested blank by regular programmer can reveal (almost) complete data at very low Vcc. NMOS chips (27xxx) is turning to "all zeros" at much higher Vcc levels.

Same trick worked for me when I tried to recover "leaked" 2816 calibration EEPROM from Marconi 2955 service monitor that I had in the past (it was Xicor part if memory serves me correctly).


73 de UA3ATQ/KI7XJ (there was typo in callsign in previous message) ;)

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Best regards,
Yuri ? ? ? ? ? ? ? ? ? ? ? ? ?mailto:yuri@...

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Hello,

Friday, July 29, 2022, 0:23:21, wspx472 wrote:

After sitting a couple of months, my 8924C now displays a "ROM Checksum Error". I also have an "E" model I bought mostly as an organ donor for the "C" model. I put the A16 card from the "E" model in the "C" model and now it boots, but thinks it is an "E" model. It is also showing hardware failures. ._,_._,_

Is there regular 27(C)xxx EPROMs? Sometimes I was able to extract original data from "leaked" EPROM chips by multiple reading at lower than standard supply voltage (I have EPROM programmer with customisable voltages and pulse widths in addition to standard profiles for EPROMS from different manufacturers). "Programmed" bit (charged gate capacitor) reads as 0, while discharged gate capacitors reads as "1". With time, capacitors discharge and some may go below threshold at regular Vcc. So, gradually decrease supply voltage and do multiple readings, to see as many "unstable/floating" zeros as you can (for manual work chip compare function may do, if locations and data of mismatches is clearly shown). At some voltage whole chip will start to read as zeros, so be careful if you will try to automate this process.

After you recombine all "lost" zeros to image files, program blank chips with this files and try if checksum is ok. Do not erase originals, sometime you need to dig for more "lost" zero bits.

73 de UA3ATQ/KI7XI

--
Best regards,
Yuri ? ? ? ? ? ? ? ? ? ? ? ? ?mailto:yuri@...

After sitting a couple of months, my 8924C now displays a "ROM Checksum Error". I also have an "E" model I bought mostly as an organ donor for the "C" model. I put the A16 card from the "E" model in the "C" model and now it boots, but thinks it is an "E" model. It is also showing hardware failures.

I transferred the 2 socketed memory ICs from the "C" model card into the "E" model card in hopes of making it once again realize it is a "C" model. It seems which model it is, is stored some place else, because it still thinks it is an "E" model. I have ordered a used A16 card off eBay in hopes of fixing it.

The A17 card from the "E" model has a bad battery. A replacement has been ordered. If I can't get the "C" model going, I hope to at least get the "E" model usable.

Has anyone else has a similar experience? Where on the A16 card is the model stored? The cards look identical.

I have an 8924C with the same problem. Looking like it is the boot ROM. HP part number 08920-87168. They seem to be unobtanium. Anyone know where I might find one?
I did try an A16 board from an "E" model, and it does boot, sort of. It now says it is an "E" model, and gives self test failures.

the error 200 means that one of the boards is not communicating or holding the serial bus down.

you may want to run the diagnostics and see what it says.? The?MSDIAGS3 will run the self test and you can see the errors there or look at the messages

kind of a PITA to troubleshoot unless you have another unit to test boards in.

The 8924 has a ton of boards in there for the cellular stuff?

If it no longer has the power-on settings saved, this suggests that the memory battery needs replacing.? Then with a new battery, to make it again act like an 8920 on power-up you can follow the instructions here:

As to the other error message, I am not an expert on this unit, but the assembly level service manual indicates that it is a serial bus communication error associated with "any non-optional assembly" and that : "This checks the ability of the Controller to communicate with any hardware on the bus."? Not that specific, unfortunately.

I would suggest re-seating various connectors, etc., that may have been disturbed during the power supply repair.? It has been years since I took mine apart to work on the power supply so I can't remember any specifics of the disassembly.

It also wouldn't hurt to try re-seating all of the modules, even if you didn't remove them for the power supply repair.? Sometimes, this fixes strange problems.

The manual can be downloaded from:



There may be further relevant information in the manual.? It's about 600 pages and I just checked for the error message in question.

Hope this is of some help.?

KE6CD

So I recapped my HP8924C power supply because I had the intermittent wouldn't power on issue. But since then I lost my power on default settings and was presented with the cell site call screen instead. My self tests now fail with error 0200 and the input power shows between 3.25 - 3.5 watts with nothing connected. Self tests point to a problem with the input module but it was working just fine before I recapped the power supply.?

I tried another power supply that I also recapped but I am getting the same results

I am suspecting one of the voltages coming out of the power supply may be slightly off, but also the power supply won't run with no load connected.?

Anyone have any pointers on what to look for?



Thank you!

Alberto,?

I hope you found the files that you needed. If not, just subscribe to the group. I believe A.18.10 FW requires a newer memory board than what I have. Let us know if you are successful.?

Greg

Hello Greg,

Thank you for your kind reply. In fact, I was not subscribed to the specific group, hence I could not find the folder with files.

Just in case you are aware of details, my 8920A is currently A.06.12, I assume there are no issues to upgrade to A.14.14, but it looks like A.18.10 may not be suitable as the notes refer to an upgraded memory I am sure is not built in.

I will try to repair this unit a.s.a.p., so that I can also upgrade firmware accordingly.

Regards, thank you again!

Alberto

On 05/12/2022 6:49 PM, Jeff Otterson wrote:

Just to close the loop on this, I sent my 8921A to Amtronix.? Rick got it all fixed, and also replaced the electrolytics in the power supply, semi-affordably.? I'm happy.

Glad Rick got you fixed up. He's always treated me fairly.

The hardest part about shipping 892x's to Rick is the packing and shipping costs. I have a box that has made a few trips back and forth to Amtronix that I save just for that purpose.

Bob...

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Hello Greg,

I also happen to have my 8920A under repair, and I'd like to upgrade FW A.06.12 to a more recent one. Do you have any download links for later firmware?

Thank you in advance.

Alberto

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Just to close the loop on this, I sent my 8921A to Amtronix.? Rick got it all fixed, and also replaced the electrolytics in the power supply, semi-affordably.? I'm happy.

73

Jeff n1kdo

Thanks everyone

From the manuals , I think that G8RPI is correct, It would be a spectrum analyzer with a 5 KHz resolution on the screen. and a freq gen.
Maybe also an audio gen and a freq counter in narrow Rx ranges.

Not as useful as my 8935.
It is also quite heavy.

Again Thanks.? Wally KC9INK

usually that goes without a problem.? Some of the programs may need the larger memory though.

Usually updating the memory is not an issue either.? The chips are still around as well,

I would backup the calibration EEPROM data first though

Almost totally useless for analog radio work. At best you get a CW RF Generator and a fairly crippled spectrum analyser.
They are not worth the space.

The 8924C is another matter. Looks the same but it is a 8920B with a GSM adaptor in a 19" box. It retains all 8920B functionality.

Robert G8RPI.

George:

Gosh, Sorry, it is the 8922M
Yea the models are significantly different.

Wally