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Thanks for the information.

There are indeed flash memory on the controller board and empty ROM sockets on the memory board. The controller board is marked 08920-60195. It's apparently not the original but it has done its job until the boot problem occurred.

/Magnus

Please, I need of diagram (schematic) of HP 8924.
thanks

I just saw I finger messed up the model it is a 8924C?
And I changed the battery so any other help would be app?

Thanks

Hello,
I have a 8921C that when starts up I get a ROM Checksum Error. Any thoughts? I ordered a new battery to replace the old one. Any other thoughts??
Thanks
Nick

Yes, it has been working well for a several years.?

Is there any reliable source of the firmware?

/Magnus

Found a bit more info. Seems the later A7 card will work with either onboard FLASH (8920B) or PROM on A8

Robert G8RPI.

on the 8920B the operating firmware is in the flash memory on the processor card and not on the? memory card.

The 8920B memory card does have a PCMCIA slot and typically the eight PROM sockets are unpopulated.

The 8920A did have two different memory cards ...early version had a smaller dynamic memory with optional memory upgrades ( option 5 )? The static memory or ROM capacity? was also smaller.? Latest firmware was rev 14.X

Later 8920A memory cards? had a larger dynamic memory as standard? ( option 05 became obsolete )and also larger? PROM capacity with version 18.X being the latest.?

Never seen a 8920A with a flash memory,??

All of the 8920A that I have worked on used EPROM's or PROM's that were programmable? from a firmware image.? ?No flash upgrade utility for the 8920A firmware that I have ever seen.

The 8922 processor card looks to be the same raw part number?08920-60395?and the boot prom part number also matches the one on a standard 8920B.? Boot PROM is socketed on most boards so it could be swapped if not the right part number.

If flashed with the correct firmware it appears that it should work ...processor cards are relatively cheap these days but as I mentioned you have to have the firmware update PCMCIA card .? Again one from an 8924 will work if the firmware is updated,

The 8920A processor board is completely different and leverages the memory card to hold the operating firmware.? Also the calibration data is not movable between series....throws a checksum error.

The program memory is not on the Controller (CPU, DCU) card A7, it's on the memory card A8. An A8 card from a 8922x won't work properly in a 8920B as it does not have a PCMCIA card slot.

Faulty memory is still a possibility so re-flashing is a good idea.

I assume you have removed and re-seated the A7 and A8 cards and any socketed chips on them?
Earlier A8 cards used EPROM or PROM chips; later ones were FLASH.

The Calibration is in a EEPROM on the A7 controller card. There are at least two versions of this card, BD25A and BD85B.

Full part numbers in the repair manuals for the A7 are:
8920A 08920-61807
8920B 08920-61872
8922? is 08920-60307 for A,B,E,F&G and 08920-60395 for H,S,M with specific ordering part numbers of? 08920-61811 for A,? 08922-61812 for H, 08922-61813 for S and 08922-61814 for M.

The M version needs a host Firmware ROM A7U65 08920-87168 which may need flashing.

So no clear evidence that a 8922 card will work...
I do have some 8922x cards knocking around.
Is your memory card FLASH or PROM?
What part numbers are on the CPU card?

Robert G8RPI

did that unit ever work correctly with that processor board ?

If so I would try to re-install the firmware for the 8920B ..latest is 6.01 IIRC? ?Takes a specific SRAM card.

It could be one of the FLASH chips? that hold the firmware is getting intermittent? ....these units are now over 20 years old at least.

otherwise I would get another processor card ....make sure you keep track of the EEPROM that is socketed on the original board and maybe make a copy of the contents since it holds the alignment data unique to that unit.

I think the card from the 8922H should work and the sticker indicates what firmware is flashed on the card .? Will not work unless the firmware is updated from the original 8922 code.

A card from an 8924 will work but you have to flash the firmware and move the calibration EEPROM over.

I have a HP8920B that doesn't boot properly. Most of the time nothing more happens than the fan starts and some LEDs on the boards turns on. Eventually it starts and runs normally after a couple power cycling's. It's getting worse and worse to get it booting.

The 5V on the controller board looks good, 5.03V and <10mV ripple. The clock oscillator is running. The reset signals is released at expected time intervals.

The controller board seems to be changed at some point. There is a sticker on it saying "For 8922H". This board must be identical or at least very similar to the original since it has been running well for several years with this.

Any suggestions?
/Magnus

Checking in - Thanks,

Mike

Nice work.

One thing to be careful about with these 2/3AA 3 pin PCB mount cells is that there are two polarity conventions. The 3V cells as used in the 8924C has the two pins as positive. The 3.6V version has the two pins as negative.

The circuit will work with 3V or 3.6V but polarity must be correct. The 3V chemistry (Lithium Manganese Dioxide) lasts slightly longer on low drain applications. It is hard to find the Lithium Manganese Dioxide cells in the UK/EU possibly due to environmental / transport regulations.

Using wire ended cells works well. A 1/2AA cell will work fine and gives more choice. Tadiran is a good make for long life. Their SL350P is a good "universal" replacement cell to keep in stock. At 1.4AH it's only slightly smaller capacity than the 3V 2/3A. It will replace AA, 1/2AA and 2/3A cells.

Robert G8RPI.

I re-worked Ralph's great job, with a few edits and additions, into a PDF file.

/g/HP8924-Family-Spectrum-Analyzers/files/HP%208924C%20Memory%20Backup%20Battery%20Replacement.pdf

Digi key has the P278-ND battery as a 1.5 volt AAA size. Are you sure you did not mean a P270-ND, which is a non rechargeable BR-2/3 Lithium 3 volt cell?

73, Bob, WX2NJ (Amateur)

I have sent a short file and some pictures of my battery replacement of the 8924C battery replacement. Thanks to the ones that responded for where the battery is located. The moderator should feel free to change the file or the pictures I sent.

Ralph ku4pt