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HP3456A bad rom



Jan 1, 1970

I successfully repair my HP3456A with information and contact from this
newsgroup. It's my duty to help others.

You will find a lot of useful information on BAMA
(htttp:// and service manual.

The HP3456A has a flaw on the ROM chip, the Mostek MK36*** dies
prematurely. The 3 chip are A3U5,A3U7,A3U8. You can replace the 3 ROM
with old Motorola EPROM MC68766. This part is a direct (pin to pin)
replacement. But you need to program them first. If your Mostek are dead
you can't retrieve the program from them. You can buy another voltmeter
and read the chip, or find the 3 program on internet, what i did.

I was lucky and find Pierre-francois Monet who repair a HP3456 a few
years ago and he open his voltmeter just to send me the 3 files.

I'm ready to share those 3 files (bin or hex)with the community. Send me
a note on this address [email protected](remove spam).

Those Mostek where use on several other HP equipment, i have files for
the HP3456A only.

If you read this on the archive and the address is not working you can
find me in the address book of ecole polytechnique of montreal.

Maxime Thibault
electrical technician

P.S. this is not a easy task and require a some equipment and skill. If
you don't have access to a universal programmer, a signature analyzer or
already remove chip from a Print Circuit board this is not a job for
you, find help. If you are close to Montreal Canada contact me.


Jan 1, 1970

I had so much success with my small offer, i never thought there was so
much dead 3456A out there.

I made a mistake in my post the 3 chip are not on board A3 but on A4.
Parts are A4U5 A4U7 A4U8. Please check service manual.

I realize that those files have a commercial value. The 3 files are
distribute freely for the purpose of keeping alive vintage electronic
equipment. I hope that nobody will use the files for the sole purpose of

I already have a few feedback from successful revitalization of HP3456A

The BAMA contributor for the hp3456A, Stepan Novotill, use the file i
sent him and split the 3 files in half to use 2532 EPROM(.bin). You have
to remove jumper on the board but according to Stepan it's working real
fine. He also sent me the ROM image of INTEL 8048 (.bin). The 6 files
for the 2532 and the rom image for the intel 8048 are available. i never
heard of any problem with the 8048 i should not send more than 1 or 2. I
will send only the file you need and request.

Please ask only for what you need.

If you have hard time finding 68766 send me a note i will try to help
(north america).

Maxime Thibault

P.S. Je parle français vous pouvez donc m'écrire dans cette langue.


Jan 1, 1970
Hello Max,

I'm glad your 3456A works fine now!
Best regards


Sep 27, 2007
Sep 27, 2007
I am searching the contact to receive the image files for the PROMs,
because I have also a dead HP3456A.