Hi
so my attempt of repairing my 34970A is not going so well so far.
I've replaced the 2 VFD drivers (putting them in PLCC sockets instead of soldering them directly).
![](https://whatever.sdfa3.org/images/hp34970a/front-panel-sockets.jpg)
But the VFD is not reacting well to my rejuvenation assaults.
![](https://whatever.sdfa3.org/images/hp34970a/front-panel.jpg)
With the VFD being dead, I was thinking about hacking the device by replacing the VFD display with a blue OLED display managed by an arduino or a nucleo that would take place of the 2 shift registers (in the VFD drivers) to decode what to display.
But I'm afraid I killed (don't know exactly how, I did nothing specially wrong when it started to fail) the U1 microcontroller of the display board yesterday evening since it does not give me any more signal on SEGDATA (U1 pin 5).
From there, I see 2 options:
- I find a replacement front-panel unit (they seem to be still available from Keysight for a bit more than 200€)
- I inspect the serial communication to rewrite a implement a new front-panel management controller.
I've looked a bit at what happens there, and it should not be too difficult.
I don't event want to try to dump the ROM from U1, since being a 87C51, it's most probably "encrypted"
(XORed with a 32bit key). And on my unit, if P1.3 pin is dead, I guess I won't be able to dump the
ROM (unless it still work as an input, sice P1 is used to set the address when dumping the ROM). I may give a try. I don't know yet.
The good news is that I've changed the FRAM chips (both on the main board and the DMM)
and it does not complain any more about these.
I have an older version and a newer version.
May be I can get the FW versions and read them out for you.
That would be awesome! Yes please!
PS: I've written a blog post on this work on my modest blog (
https://whatever.sdfa3.org).