Hello, In October 2012, my Swedish localized CBM 610 (upgraded to 256K RAM) suddenly died in the middle of operation. When I power it on, the LED lights but I don't get a video signal. Any IEEE drive connected to the bus keeps spinning forever. In case it'd boot to Basic anyway, I tried CTRL+G to check for any bell sound but nothing. While I don't have much of skills with troubleshooting, at least I have some spare parts and tools. Yesterday I took it apart and found that the Kernel EPROM adapter had a leg partly missing and replaced with solder. I found a proper 2764 -> 2364 adapter and replaced it, but no difference. All three EPROMs (Kernel, Basic High & Low) read out fine with my EPROM programmer and match the already dumped binaries. The next step was to look at the PLA. On this machine the original chip was purposedly (?) misaligned by one pin, meaning the top pins are in the position of the second row of pins and the lowest pins not connected. I don't know if this was due to the RAM upgrade but the machine used to work fine like this. In any case, I plugged in my SuperPLA Multi configured for a 610, but no difference. I never tried the 710 setting. Out of the other chips on the motherboard that are socketed, remains the character EPROM, 6509 and 6526. I happen to have a working 710 minus keyboard, but I haven't tried to swap CPU between the two. I saw there are schematics and a service manual on Zimmers et. al. Are there other documents of troubleshooting elsewhere? Would it be a good case to swap CPU, at least put the one from the 610 into the 710 to see if the latter still boots? I suppose I could measure voltages here and there, if anyone likes to guide me through what to measure and where. However I don't own anything like an oscilloscope. Best regards Anders Carlsson Message was sent through the cbm-hackers mailing listReceived on 2013-01-23 15:00:08
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