RE: Motherboard versions

From: Raymond C. Bryan (
Date: 2001-07-26 18:12:49

My experience repairing Commodores has shown that static (lightening 
and your fingers after a walk on the winter-time carpet) is the most 
destructive  to chips inside. Most susceptible is the PLA in 64s rev 
A to rev D motherboards (about half of the light color flatter 64s 
are rev D) In Rev E the ram is most susceptible.  In both the 
6526/8521 CIAs and 6581/8580 SIDs are static sensitive and not 
isolated from the outside ports (user, joystick, video/audio, tape, 
expansion).  MOS used plastic packaging on most of its chips in the 
64s except 656x video chips which are almost all ceramic and less 
susceptable to packaging failures.   Power supply failures usually 
wiped out RAM in a zig-zag pattern that is every other one in the row 
and each row offset by one.  The TED is alas very susceptible to 
damage from power flux or static and so C16 and +/4 in good working 
order are more scarce.  1571s used a leaf spring suspension for the 
upper read/write head that will tear and thus not put proper tension 
on the disk to read.  Especially this happened when the drives were 
left open (spring up) no disk in the drive!


>  >Perhaps we could gather together some informal data on the relative
>>popularity of the well known CBM types.
>Hi Guys, (this is a reply to a question on the old list)
>Most of my computers have been collected from the recycling centre, so
>perhaps not the best place to find working samples :)  but believe me, the
>statistics below are based on a sample large enough to be too embarassing to
>admit to!
>58% of my C64 machines are the brown bread box
>67% of the brown boxes work, 78% of the beige case models
>all of the SX models work - only have three though :)
>86% of the C128 machines work, though 25% I've repaired (bad RAM)
>90% of the C128D machines work
>43% of the VIC20 machines work (50% of the original PAL)
>16% of my C16/Plus4 machines (thanks to Ruud! for the CPU)
>Compared to my non-CBM machines, the Commodores seem to be very poor when it
>comes to longevity. Most I assume are RAM failures due to dickie power
>supply regulation....
>Disk drives fair better with most types having a working status of better
>than 90%, except for alignment, the next biggest problem is ROM failure.
>I hope the above is not too trivial, but would be interested to know if the
>above is typical.
|Raymond C. Bryan  651-642-9890 vox      | The battle is sometimes |
|Raymond Computer  651-642-9891 fax      | to the small for        |
|795 Raymond Ave   -email:  raycomp      | the bigger they are     |
|St Paul MN  55114          | the harder they fall.   |
|USA              Amiga - Commodore      |     -- James Thurber -- |

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