Hi Ade,
I have downloaded your Data.txt, and wondered how you did it ?
I am also working my way through a the HP8921A. I also found C7 in the power supply blown.
I bit the bullet and replaced all the electro capacitors and the poly caps. The C7 capacitor is a 0.047 uF, which I replaced with the same value but a bit higher voltage 630V.
I ran the PSU outside the instrument, i.e., bare on the bench and measured the outputs no load.
The HP displayed "Unable to read the Memory Rom, which I now know is that the memory battery is flat. It is located on the Memory board, which is the far right hand board . (instrument facing you).
My HP has a PCB mounted LIPO Battery. I found a "VARTA" 3V non-rechargeable PCB mount in OZ from Queensland, which is coming now in the Post.
As a temporary measure, I bought an ordinary LIPO from my local hobby electronics store, which got the screen up and revealed more errors.
The 4 LEDs on the edge of the ?CPU board, gave me a clue. read the Assembly level manual and it will give a list of the errors in hexadecimal. My HP indicated the receiver board was faulty and that it had a bus fault. Fortunately, I have another HP8920A, and I marked the modules before I started swapping, then swapped the receiver module. All is now ? working better, but still an error 0200 is there, so the bus is not happy.
Like yourself, I do not have any PMCIA cards. I am thinking af how to dump the ROM data into a PC and archive it for future use. I am also thinking about how to adapt a normal PMCIA to USB card to permit communication I/O . My HP has the RS232 port on the back, which I may be able to communicate via too. I have an old Win XP Toshiba laptop with a DB25 Connector, perhaps that can become a terminal using some "Basic" language . I see that HP use IBASIC language. So I think I have found a download of the program, which I will play with in coming weeks.
So we should dialogue some more on this quest Ade.
Regards
Bill M.? (VK6II)
