Subj : Re: Two Commodore 64's th
To : Clocky
From : Dennis Katsonis
Date : Mon Oct 19 2020 09:36 pm
-=> Clocky wrote to Dennis Katsonis <=-
Cl> 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).
Cl> Black screen is often a failed PLA. These can be replaced with modern
Cl> 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.
>
>
Cl> What supply are you using? If it's an original Commodore brick you
Cl> should test the voltages first as they commonly fail and when they do
Cl> they destroy the computer attached to it.
Cl> Better still get at least a power saver or better still a modern
Cl> 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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