PAL-II RAM problem?

[John Bischoff]

I've been using my PAL-II for a number of weeks now with no problem. I've been able transfer my old waveform generating code from 1979 into the PAL (via the TTL Serial device) and single-step through it to re-familiarize myself with how it worked. All was going well until suddenly today the program crashed when I tried to execute the next step. I pushed Reset and tried to re-initialize the vectors at 17FA and FB and 17FE and FF. The most -significant bit on those locations appears to be stuck on "1" so when I try to enter "00" it reads "80" or entering "IC" reads "9C."

Has anyone had the 6532 RAM chip fail? Or maybe a smaller support chip to the 6532 failing which would have the same effect?

Many thanks for any suggestions.

John

[Ronny Ribeiro]

I have never had any problems with any of my 6532s, but I did get some spares because these little devils are old and are going to get scarce. 

So my advice to any owner of a PAL computer: get some 6532 and 6502 spares. You can find them at AliExpress.

Have tried to swap around the 6532s on your PAL-II?

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[GN Liu]

It seems that D7 stays high, as you described. You can check if there are any shorts around pin 26 on U2.

The PAL-II uses all 128 bytes of RAM in the RIOT at U2. If the RAM in U2 has failed, you can swap U2 and U3 to use the RAM from the other 6532.

The 6532 chips had a relatively high failure rate when I purchased them. I’ve encountered issues with the timer and data line output, but as far as I can recall, I haven’t run into RAM failures. That said, faults can occur in any part of an old chip. If the RAM works normally after swapping U2 and U3, I’d also recommend keeping a backup or two of the 6532 as well.

Liu

[John Bischoff]

Thanks so much for the helpful suggestions on the 6530!

John

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John Bischoff, composer

www.johnbischoff.com

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