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My lazy PET 2001-8N doesn't like to boot up. But it will - after a while.

R

retrobits

Experienced Member
Joined
May 22, 2007
Messages
169
Location
Portland, Oregon, USA
When I turn on my PET 2001-8N, sometimes it takes a while to display the Commodore welcome message. Sometimes it doesn't come on at all. When it does come on, everything works well. The screen is crisp and it functions normally.

The CRT always turns on, even when the welcome message doesn't appear.

Any thoughts on where to start troubleshooting?

Thanks!

- Earl
 
retrobits said:
When I turn on my PET 2001-8N, sometimes it takes a while to display the Commodore welcome message. Sometimes it doesn't come on at all. When it does come on, everything works well. The screen is crisp and it functions normally.

The CRT always turns on, even when the welcome message doesn't appear.

- Earl
Click to expand...

Earl, I have no idea specifically what's wrong, but it does sound like it might be a geriatric capacitor warming up (or sometimes not warming up enough!) to get within tolerances. If it was an IC, I'd expect an all or nothing symptom, yes?

Tez
 
Mine does this, too. I think it's RAM but never really cared to diagnose it. If I use it regularly it doesn't do it.

It's been months since I turned it on, so it's being very stubborn.

 
Oops .... thats not a well PET KC9UDX!


Earl, try looking at the voltages to see how they change over a short time ?

Also look at the clock and reset lines also.

Andy
 
AndyG said:
Oops .... thats not a well PET KC9UDX!


Earl, try looking at the voltages to see how they change over a short time ?

Also look at the clock and reset lines also.

Andy
Click to expand...

I agree, it might be the reset line taking too long to lift (look around the 555 reset circuit and its R/C timing components). I wouldn't suspect the clock generator since it would produce no video if it failed completely, but it might have a fault on the very last gates that deliver the clock signal to the CPU (check pins 37, 3 and 39 of the 6502).
It might be the IRQ signal staying low for a while too (check pin 4 of the CPU).

Frank IZ8DWF
 
AndyG said:
Oops .... thats not a well PET KC9UDX!
Click to expand...

It's been this way as long as I've had it. I would have fixed it when I had it on the bench, but it has to be turned off for weeks or months to make the problem happen long enough to find it!

It doesn't bother me because of I use it once in a while it doesn't do it at all.
 
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