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I just bought a 3562A that was on ePay and received it today.? It appears to boot without issue however the characters displayed are (mostly) incorrect:



Pressing the PRESET key leads to this:



Pressing other key combinations seems to work for a while although the unit eventually locks up.? The NVRAM battery is completely dead but that should only throw errors, not this.? I know these have a digital display that is shared among other units but I have no experience with them.? I bought the unit for a decent price with a free return policy so I'm not really at risk with it - but I would very much like to keep it if repairing it is feasible. That being the case, I would very much appreciate any help or pointers as to whether or not repair is a worthwhile thing and, if so,? pointers as where to start looking.

Thank you all!

Hal

Is there a correspondence between correct and your characters?? For example a bad bit being transferred?

Not really sure at this point - most numbers seem to be correct, but not all letters are incorrect.? At this point I have not done much other than play with the menus and reseated a few boards.? I don't want to really tear into it if I'm going to wind up sending it back.? I *think* I remember reading at one time about the display units in these and I'm pretty sure that they have their own character generator - so the error could solely in it or in the connections from the main unit.? I'm mostly hoping at this point that someone else as run into this issue before.

A goofed up character generator (ROM) or maybe a dodgy address line to the character generator would be my first guesses. Address buffer chip gone poof maybe?
I do not expect this problem to be caught by POST.

Wilko

The display module is the HP 1345A.

There are two versions, one which includes display memory that
it uses to continuously refresh the display, and the other version
does not have the display memory, and requires the instrument's
processor to continuously send display data to the display module.

According to the 3562A service manual vol 2 (from Artek Media), page
8-145:

The A84 Memory Option assembly is not installed on the HP8562A/Hp8563A, jumper packs A82 U3 and A82 U4 must be installed.

According to the 3562A service manual vol 1 (from Artek Media)




Separate from the above, the 1345A display module will go
into the above test mode if the 26 pin flatflex is unplugged.
(There is a cable disconnect signal on one of the pins).
Accessing this may be difficult within the 3562A.

So, the above mentioned A17 W1 is a jumper on a 3 pin header
that is visible through the single hole in the shield over the
display module. You only need to remove the top cover to
access it.? I just tried this on my 3562A, and I found the following:

1) You can just remove the jumper (middle and pin towards the back),
it does not need to be place into the middle and pin towards
the front position.

2) you can remove the jumper with the power off

3) be careful not to drop the jumper into the guts of the instrument

4) The above test pattern has some limited text.

The Character ROM is within the display module and is almost
certainly HP custom unobtanium, because the font is a vector
font that is scalable.

The 1345A has additional test modes, but I don't think that
they display text.

Good luck,
Philip

It's worth knowing that the variant of the display in the 3562 is different from most other 1345A units. The 3562A service manual includes schematics and these are the best ones to use.? Foolishly I started with (several different)1345A manuals which were excellent from a general understanding point of view of the interface and commands but quickly throws up lots of specific differences on the boards.

The self test (just remove the IDC cable) with Pikes Peak is a very good place to begin.

Alan