Two Commodore 64's that w

[Andreas Kohlbach]

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).
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.

No specific idea. But the Youtuber Adrian's Digital Basement
<https://www.youtube.com/channel/UCE5dIscvDxrb7CD5uiJJOiw> fixed a lot of
dead or half-dead Commodores 64. Search his channel for "Commodore 64",
may be one of the videos is helpful in your case.

[Clocky]

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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[Dennis Katsonis]

-=> Clocky wrote to Dennis Katsonis <=-

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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[Gary McCulloch]

.-: On Mon 19-Oct-2020 9:36p, Dennis ***@1:124/5016.0 said to Clocky
DK: chip failed. With three boards, I should be able to get one working from
DK: parts, but it won't be easy.

But it will be well worth it!

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[Dennis Katsonis]

-=> Gary McCulloch wrote to Dennis Katsonis <=-

GM> .-: On Mon 19-Oct-2020 9:36p, Dennis ***@1:124/5016.0 said to
GM> Clocky DK: chip failed. With three boards, I should be able to get one
GM> working from DK: parts, but it won't be easy.

GM> But it will be well worth it!

Absolutely. I have a multimeter now, so I can perform more troubleshooting.
One I think the problem is the switch, the other isn't supplying enough voltage
to the chips, though the voltage regulators are outputting the correct voltage.

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