Electronics > Repair

HP 3468A does not complete self-test, the LCD display all on.

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StrayElectrons:
Hi here,   First time posting.

S/N 2137A02728 and also the battery option 001 but I'll leave this battery's board disconnected via the ribbon cable at motherboard's also the lead-acid battery removed.   No leaks luckily.

I do have 5V (4.99V), +15V and -15V and ">7V" is around 12V.

The LCD display is all on including dots and commas as well instantly at turn-on.  Didn't exit the self-test.  Posted this picture.

I'm aware of basics to check for but I wanted to post here to get your thoughts.   I know this model does have ROM IC that usually develops bit-rot but wanted to check anything else first then suspect the ROM last.

I do have multi-meter and scope but I have to clear my crowded bench first.

Cheers,

cruff:
That's the indication that it hasn't exited the self test, as you surmise. Do you have a copy of the service manual? It's available from several sites with a search.

Section 7-D-14 Self-Test says the order of the tests is ROM, RAM, cal RAM then the A/D converter. If all of those pass then the "SELF-TEST OK" message is displayed.

7-D-21 is the turn on failure trouble shooting section, there's lots of checks in that and the following sections to narrow down what might be wrong.

Tj138waterboy:
It would be in your best interest to check out the rifa caps at the iec connector as well. NFM youtube video with replacement caps for a 3478a has link I used digikey cart https://www.digikey.com/short/72j411bn

StrayElectrons:
Thanks!   Do you have the laundry list of items in text?

Reason:
Clicked this and got the message: Due to restrictions, we are unable to add this item to your order

Cheers,

Tj138waterboy:
Sorry im working off mobile phone but I was able to cooy and paste web addrrss and it worked fine

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