Clocky wrote to Dennis Katsonis <=-
On 4/10/2020 2:32 am, Dennis Katsonis wrote:
Subject: Two Commodore 64's that wont power on
I have just received FOUR breadbin Commodore 64s. One is missing the mainboard, one turns on, but with a black screen, and two don't turn on
at all (power LED does not light up).
Black screen is often a failed PLA. These can be replaced with modern equivalents.
When our lockdown ends, I'm going to get a multimeter, but I'm wondering
if there is a common and obvious cause for this that I could look at
before I get a multimeter (which may not be for weeks because our state premier likes to imprison us).
I've looked at the fuses, one was broken, but putting the good fuse in
both machines didn't work.
What supply are you using? If it's an original Commodore brick you
should test the voltages first as they commonly fail and when they do
they destroy the computer attached to it.
Better still get at least a power saver or better still a modern replacement power supply.
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I'm using an original power supply, but it works fine on one other machine. That doesn't rule it out, but it makes it less likely.
I did switch the PLA with another machine to no effect. I suspect it could be RAM. Bad RAM I think can cause this. I do recall that one machine would start, but only have 27 bytes free. So perhaps the last remining working ram chip failed. With three boards, I should be able to get one working from parts, but it won't be easy.
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