Re: CBM 610 troubleshooting

From: Michał Pleban <>
Date: Wed, 23 Jan 2013 15:46:01 +0100
Message-ID: <>

Anders Carlsson wrote:

> Any IEEE drive connected to the bus keeps spinning forever.

That would indicate either that the RESET signal is applied forever on
the IEEE bus (rather unlikely) or some signal lines are set with a wrong
state on the CIA output port (more likely). In the latter case, the CIA
would be a prime suspect. I have seen several 610's and 710's not
booting due to a broken CIA. You should try to swap it.

> 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.

Misaligning the chip has nothing to do with RAM upgrade, the 610 will
take upgrade to 256k without any PLA updates. I seriously doubt it would
ever work with a misaligned chip unless some additional wiring and
soldering was done (a misaligned PLA chip will not get power).

The 710 PLA has different pin assignment so will not work in 610 anyway.

> 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?

You can try to swap any chips but definitely start with the CIA.


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Received on 2013-01-23 15:00:50

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