which chips fail the most on the 64

Disk drives, Monitors, SuperCPU etc.
User avatar
Gyro Gearloose
Member
Member
Posts: 315
Joined: Sun Nov 15, 2015 5:20 am
Contact:

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".


The price one pays for pursuing any profession, or calling, is an intimate knowledge of its ugly side.

banman
Member
Member
Posts: 104
Joined: Sat Jun 15, 2019 12:21 am
Contact:

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.

User avatar
eslapion
Member
Member
Posts: 932
Joined: Mon Jul 20, 2015 10:11 am
Location: Canada
Contact:

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.
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

banman
Member
Member
Posts: 104
Joined: Sat Jun 15, 2019 12:21 am
Contact:

Re: which chips fail the most on the 64

Post by banman »

Hi eslapion,


Absolutely agree with you!

Just looking on eBay and found this....


https://rover.ebay.com/rover/0/0/0?mpre ... 4194209389

Not an expert on these dates but looks like they might be fake.....

User avatar
eslapion
Member
Member
Posts: 932
Joined: Mon Jul 20, 2015 10:11 am
Location: Canada
Contact:

Re: which chips fail the most on the 64

Post by eslapion »

banman wrote:
Sat Jun 06, 2020 4:13 am

https://rover.ebay.com/rover/0/0/0?mpre ... 4194209389

Not an expert on these dates but looks like they might be fake.....
Yeah, that a total hoax. This says it's an NMOS 6522 made the 2nd week of 2002. Commodore vanished in 1994...

The correct current replacement part for a vintage 6522 such as those found in the VIC-20, VIC-1540, VIC-1541, 1541 and 1571 drives are these:

W65C22N6TPG-14 from Mouser
https://www.mouser.ca/ProductDetail/Wes ... cBoQ%3D%3D
Wealth, like happiness, is never attained directly. It comes as a by-product of providing a useful service. -Harland D. Sanders

User avatar
Gyro Gearloose
Member
Member
Posts: 315
Joined: Sun Nov 15, 2015 5:20 am
Contact:

Re: which chips fail the most on the 64

Post by Gyro Gearloose »

That's nothing, here is a chip made in 1922.

https://www.ebay.com/itm/1PCS-IC-MOS-DI ... 0005.m1851

Unless it's a time traveling Bigfoot from 2022?

Well good to know the world is still there in 2022...
The price one pays for pursuing any profession, or calling, is an intimate knowledge of its ugly side.

rmzalbar
Member
Member
Posts: 148
Joined: Wed May 08, 2019 9:06 am
Contact:

Re: which chips fail the most on the 64

Post by rmzalbar »

Yeah, I have several remarked MOS chips. They all work fine. Sucks that they resurface and remark them, it doesn't benefit anyone to do that, even themselves, as original condition would be worth more. The shiny leads from solder potting them are a dead giveaway in cases where the date codes aren't obviously wrong.

Even though they work, you then have potential issues such as revision faking. Is it really 6526A or just 6526? Is it really an 8500 or a 6510? Which VIC-II revision really?

banman
Member
Member
Posts: 104
Joined: Sat Jun 15, 2019 12:21 am
Contact:

Re: which chips fail the most on the 64

Post by banman »

Gyro Gearloose wrote:
Mon Jun 08, 2020 3:22 pm
That's nothing, here is a chip made in 1922.

https://www.ebay.com/itm/1PCS-IC-MOS-DI ... 0005.m1851

Unless it's a time traveling Bigfoot from 2022?

Well good to know the world is still there in 2022...


LOL :lol:

banman
Member
Member
Posts: 104
Joined: Sat Jun 15, 2019 12:21 am
Contact:

Re: which chips fail the most on the 64

Post by banman »

Something happened to me recently.

It's not exactly a chip which fails on the C64. However I feel it is something to watch for.

I have been doing quite a bit of testing of some chips on the C64 mainboard. My best practice testing procedures can be sketchy at the best of times. :lol:

I couldn't get the C64 to boot,I thought something had failed. Possibly something I failed to do or I caused.

I went thru and checked some voltages. It appeared that the 5v running from the on-board 5v linear regulator was reading low. I pulled every thing off the board in an attempt to track down what I thought was a shorted component (my thought was it was an IC). NO luck.

I even removed the RF modulator thinking it was shorting out (that was a big job).
Someone above must have been watching over me cause thankfully I didn't pull any traces off anything on the C64 mainboard.

I was lucky enough to have the brainwave of hooking up this RF modulator to another C64 board with jumper wires to see if it caused a short on this known good board.
The RF modulator actually tested OK. No short.
OK, I have a C64 mainboard with only the CIA's on everything else off including the RF modulator.

I checked the C64's power switch to find the 9V ac side was partly working. The volt meter showed about 20 Ohms resistance.

I used some silicone based spray (the clear watery stuff) and worked the switch quite a number of times until the switch showed good continuity. I must admit the switches are constructed very robustly. I would hazard a guess it was some surface corrosion on the internal contacts.

It all worked again after putting everything back along with all new RAM chips in newly installed sockets as well as the RF modulator, thankfully!

It gave me a real life lesson to check thoroughly everything starting from the wall outlet back thru the C64! :oops:

Post Reply Previous topicNext topic

Who is online

Users browsing this forum: Majestic-12 [Bot] and 1 guest