which chips fail the most on the 64

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Gyro Gearloose
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which chips fail the most on the 64

Post by Gyro Gearloose »

I mean we all know the PLA fails whether we take care of it or not.
I think in general what fails next are the DRAM chips, with maybe MOS support chips like 8701 type of things?

Has anyone complied actual numbers about what chips fail in a 64?

I mean as hot as it runs I don't think I've ever had a VIC-ii fail, but that's just me.

SIDs can fail especially when something is plugged into its "audio in".


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banman
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Re: which chips fail the most on the 64

Post by banman »

Hi Gyro Gearloose,


Here's some pics of dead chips I've collected from repairing 6 X C64's.

Apologies in advance for the poor photo quality..

IMG_20200419_175404.jpg
CM200419-175135001.jpg
memory chip
CM200419-175152002.jpg
memory chip

Image
U8 ? Alternatives 7406 or 74LS06

Image
U4 Kernal ROM

Image
U7 MOS 6510 CPU

Image
U18 SID Sound chip

Image
U2 CIA chip

Image
VIC II sockets

Image
2X VIC II chips

Image
PLA chip



And 2x electrolytic capacitors in the VIC II shielded area.

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eslapion
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Re: which chips fail the most on the 64

Post by eslapion »

If I rely on Ray Carlsen's experience whom has fixed hundreds of Commodore computers, including the various versions of the C64, various revisions of the VIC-20, Plus/4 and PETs, the 2 most frequently failing ICs in the C64 are the 28 pin PLA and DRAM ICs.

Incidentally, I make and sell PLAnkton and Saruman-64 which replace these.

Please note the 64 pin PLAs (there are 2 versions) used on C64c board 250469 fail quite rarely.

Unfortunately, the 3rd and 4th most frequently failing ICs of the C64 are the CIA (MOS 6526 or 8521) and the various versions of the VIC-II and there is presently no replacement for them.

In the case of the VIC-II, the 856X used on the C64c 250469 use only 5Vdc and they produce much less heat so they fail much less often. These HMOS version of the VIC-II are normally installed on boards 250469 but they can very easily be adapted to earlier boards. It's only a matter of rerouting pin 13 which receives 12Vdc on the 656X but receives 5Vdc on the 856X. Plugging a 856X directly on older boards will destroy the chip because of that.
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