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.

 > ... MultiMail, the new multi-platform, multi-format offline reader!
 > === MultiMail/MS-DOS v0.29
 >

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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