8032 chirping continuously, PETTEST can't execute the full RAM test

[anti77]

Another PET 8032-sk, board assy 8032030, pettest gave initially:


Bad between characters 64 and 127, that was a D6 issues, so I replaced UA6 and UA7. Then it passed Page0/1, however now gives this weird screen repeating "k dram memory test" and monitor high voltage shuts off in a few seconds:



Seems like it never goes to test the ROMs (or my eyes refresh rate can't catch it), and it breaks during the memory size detection/test. Here is the board:

What should I do next?

 

[anti77]

nevermind, this time piggybacking worked, and replacing UA10 now PETTEST is passed the ROM test, now is running the RAM test throwing some more mem fail messages

 

[Gary C]

Ah, the repeating text, I had that.

https://forum.vcfed.org/index.php?threads/8032-sk-restoration.1238887/page-8

 

[daver2]

Yep, all RAM faults in pages 0 and/or 1 - which equates to the lower 16K.

Dave

 

[Radix]

You can pretty much expect most of the ITT 4116 DRAMs (especially the ceramic ones) to be faulty, sadly - the other makes are much better - I have seen between 8 and 16 of them on a given board faulty - replacing them all is tedious, I would suggest a 32KB Static ram replacement and have done with it!

 

[anti77]

Got away easy by replacing only 5.

Only 3 needed to be unsoldered. Two were already in a socket. Passed the PETTEST memory test about 0x12 times.

Now Supersoft HR80 board added, everything works



Just that I can't close the case. The transformer in the 8031-SK is mounted under the monitor and touches the addon board...

 

[daver2]

Well done with the logic.

I can't help you with the mechanical aspect though!

I know a man who will make it fit - but you might not like the results...

Dave

 

[anti77]

With a multitool I've cut about 15mm from the left plastic mounts, 8mm from the middle mounts, and case closed (literally). The motherboard sits slanted a bit, that's not seen from the outside, the tape port is where it should be and accessible.

Now I have to figure out why the keys write all garbage. Hopefully I just messed up soldering the DB25 connector from this schematic. I will have to test starting shorting rows/columns at the motherboard then the DB25 female ports and tracing it to the inside of the keyboard, but today is late in the evening for that.

Worst case I will have to patch the Supersoft HR80 board's ROM that has the edit ROM and the keyboard mapping I assume.

Thanks again @daver2 for the PETTEST, it's a great help for finding bad RAM chips.

 

[dave_m]

Excellent troubleshooting.