Electronics > Repair

The repair from He!! - HP 4275A LCR meter

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Dany:
Hello,
i have a lcz meter mod. HP 4274A not working.
I would need to have the 32K ROM image marked 1818-1137 (A9U7).
I'm also willing to donate for anyone who helps me or who gives me directions where to download it
Thank you
Daniel

_Wim_:

--- Quote from: Dany on March 28, 2023, 04:54:10 pm ---Hello,
i have a lcz meter mod. HP 4274A not working.
I would need to have the 32K ROM image marked 1818-1137 (A9U7).
I'm also willing to donate for anyone who helps me or who gives me directions where to download it
Thank you
Daniel

--- End quote ---

I believe the 4274A and 4275A use the same firmware. This would mean you can use the ROMs posted here: https://www.eevblog.com/forum/repair/the-repair-from-he!!-hp-4275a-lcr-meter/msg1490586/#msg1490586

Swake:
Thanks for digging this thread up from the past. It was a vert interesting read! Many things to learn from.

Dany:
Sorry, in part it is true only for the 32K U1, U3, U5 and U10 rom for the U7 rom there is a difference in fact in the HP4275A it is marked 1818-1138 while in the HP 4274A it is marked 1818-1137 I need the image of the latter
Thank you
Daniel

GRMPhD:

--- Quote from: Dany on March 28, 2023, 04:54:10 pm ---Hello,
i have a lcz meter mod. HP 4274A not working.
I would need to have the 32K ROM image marked 1818-1137 (A9U7).
I'm also willing to donate for anyone who helps me or who gives me directions where to download it
Thank you
Daniel

--- End quote ---

Wow, what a coincidence that I am working on my faulty 4274A only a couple days after you and came across the same thread!

I desoldered and dumped all of my ROMs and posted them in the attachment to this reply.

My 4274A is not working so I can't guarantee that my ROMs are good, but if I verified them against the dumps already posted in reply #48 by precaud and they do agree for U1, U3, and U5. So potentially my U7 and U10 are also ok, but like you, I was unable to find any dumps of U7 or U10 from a 4274A online to verify that mine are OK. I'm not sure why the ROMs posted earlier are 4k. Looking over the service manual it appears that there are only 11 address lines (2^11 = 2k) connected to the ROMs so my 2k dumps should be all that the instrument is expecting. I dumped them with my MiniPro programmer assuming they are a type 2716 EPROM. I know this is an incorrect assumption, but without being able to decode the HP part numbers and see what the chips actually are I'm not sure what else to try. Hopefully, if you are able to get yours working using my ROMs then I can at least rule out my ROMs being the problem.  :-+

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