Factory sockets for chips that you don't see normally in sockets could be a result of the chip supply issue you mentioned. The factory needs to keep production flow steady with no line stoppages, so to work around parts shortages they just complete the soldering of boards with sockets in place of missing chips, and put the almost complete boards to the side. When the chips eventually show up, they can be installed in the sockets just by hand by pretty much any assembler to complete the boards, without needing to be soldered by someone who's skilled enough to do rework.
That's a really interesting theory and really makes sense. I wonder how many vehicles, PLC's and all sorts of other devices over the last 12-24 months may have socketed IC's. A silver lining for the recent chip shortage cloud.
@nine I don't think it's for the repair necessarily. I think they knew the chips they had on hand were so bad, that the odds of just soldering one in and have it work would be a little low, so they had to try a few to begin with. Thus the sockets.
Not gonna lie, I love seeing my name roll with the credits. Thanks for putting these out early for us, Adrian! Well done, as always. It is pretty amazing the level of production quality you produce these videos with in such a short period of time.
Brilliant explanations! Love the way you explained the PLA failure modes and how you determined that the PLA was fine. I am happy that I recently got a scope, too. I habe a 1541 to repair and it seems one of the logic chips is broken (ROM and CPU I already replaced with working ones)
My first C64 (Spring '84) had all the problems you speak of. I was a kid at the time, but I remember for sure the SID being replaced at the repair shop, and I believe the other time it was the PLA. Ended up getting a C64C in '88, but can't remember the problem then.
Some advice: Remove the chip first before you clean off the thermal compound. If you smear it while it's in the machine the IPA can cause it to flow around and crust onto other parts, making it harder to clean. Especially if it gets into a socket.
On the topic of thermal compounds, while they are not suppose to be electrically conductive, I personally would not leave it going across the legs like that. I'm sure the VIC from the first machine in this video is bad (your testing is very thorough!! Always enjoy it :)) .. is there the possibility that maby it could be contributing to the output we say with it in the "ZIF C64"?
@@nathanielbest3541 I would think there is some electrically conductive components in thermal paste, at least some of the higher quality ones...not enough to cause a direct short, but perhaps a resistive shunt. I could be off-base here, though.
I would bet they installed the sockets because they were out of these ICs at the time the board was soldered, and just later stuck in chips once they had any. That way they can keep the assembly and wave soldering line running even with supply problems.
Watching this repair-a-thon makes me only hope it is just the PLA bad on my Rev A C64. On the other hand a repaired C64 requires an 8 bit dance party every time.
Commodore was notorious under Jack Tramiel for cutting corners. No surprise seeing their chips failing years later and few socketed chips on the boards. Every pinched penny added up! Conversely, I rarely have heard of Atari chips failing. They even used POKEY sound chips even in their coin op arcade games! 😉 The 2600 chips would fail but that thing got heavy use.
It would be interesting if you had a small spreadsheet of the contents of your dead parts bin with different C64 chips and revisions and date codes. To see what the most failure prone of the parts were.
"Good bye horrible paper RF shield!" *clank* In other news: "There are several police reports of unexplainable openings and closings of automatic garage doors in the a Portland neighborhood, which especially frequent happen on (mail call) Wednesdays".
Another idea for a diagnostic tool would be a small device that would blink if more than one chip select like was active. Or some kind of high impedance light that uses the CS as a ground to light up. Then you could watch chip select in real time.
Don't socket the SID. They're really sensitive. At least wait until it's dead. My first SID removal was done by my ham-fisted younger self with a crappy soldering gun and the SID was almost dead (some waveforms on some voices still worked). The second time I tried removing a SID I was being careful and using a solder sucker. The SID worked, but the filters were bad. Sucks on the more awesome tunes. The third time, I was extra careful and even took time after each pin to allow the chip to cool down. Still blew the filters.
you know what, now you've got me wanting to dance with you on the 8 bit dance party, caught myself doing it while you were too, i dont think ill ever get sick of you fixing up old commodore 64's thanks again adrian for you great content please keep the videos rolling in
I'm thinking that the uncommonly socketed-from-the-factory chips are from when a board failed it's first run through the production line and it was reworked at the factory until it was functional, then it was finally sold. Whatever the case, convenient fix!
interesting video has always, but maybe is a stupid question you said that two multiplexor are bad! it can't be possible that only one of the two was broken you had test all two chips off camera ? looking forward for the next video :) greetings from italy
Awesome that they're back up, other than the missing SID and VIC in the first one. I WISH I got MOS Logic chips in sockets like that more often than I do, which is hardly ever. I just replace those with new TI parts whenever I see them, as I resell them and I can't trust the MOS chips if working today will work tomorrow.
Kind of what I was thinking. Lots of trauma to multiple chips. It would be... rare? For multiple chips to just fail at the same time. You’d think one chip would fail then it would get shelved.
Interesting as always. I now have to wonder about the breadbox C64 I once had... it was from the same era as machines 3 and 4, paper shield and all. It was a Christmas gift in 1984. But by the time I sold it in the early 90s, it had a full set of new RAM (thanks to the factory power brick bricking my 64) and a new VIC-II (thanks to my kid sister pulling a game cartridge out with the power on... only one bit in one register was bad, but it made many games unplayable until I bought a new VIC-II chip in the late 1980s).
"you know it's an NTSC unit because it has a FCC sticker on it" With that comment, I can only think of my GameCube Game Boy Player. Add-on for which the one I bought is orange, which I'm almost positive was a Japanese-exclusive color yet has an FCC sticker on it which would not apply to that market. :D
Yeah, he's used his minipro to test LS chips in previous videos.. I think in the case of this specific one, there wasn't really a point. He had spare versions of those specific chips. I'm not sure both of those were bad and maybe it would have been good to run it through the tester just for completeness, but he probably didn't want to use those MOS chips even if one of them was still good since it's a matter of time.
Seeing this a couple of years later.. I do agree that the VIC is still an issue as Kawari isn't that available and still expensive so mostly for uber nerds building new systems. But the SID while sure it would be nicer to have the original there's always the goto ARMSID which even back when this video was made is decent and fair priced and it supports mouse and paddles unlike lower priced alternatives. Now there's even a few more replacements including FPGA and open source intivaties which although lacks ready made PCBs for the masses to become real alternatives.
Not really, MOS PLAs from 1985 onwards are reliable, and don't get as hot as the early ones. There are quite a bit of machines with those. You just don't see those machines appear in videos because they don't break as often.
@@danielmantione Ahh you mean the newer ones in the C64C wedge model? Yeah those were solid. Maybe there was a breadbin 85 model with solid ones I guess Ive never seen/experienced an 85 bread bin c64. All mine are 84 and prior.
@@joshhiner729 The C64Cs are tanks; near indestructible, but they were only introduced in 1986. I was talking about breadbins that are reliable from 1985 onwards. Lots of breadbins were produced in 85 and 86 and even after the C64C was introduced the breadbin was still being made in smaller quantities. If you do an image search for "assy 250466" on Google you will find photo's of some later breadbins and you can look at the datecodes of their PLAs.
@@joshhiner729 If it is just about the breadbin case, look for an Aldi C64 or C64G (those were the final breadbins). They have the short boards though. Regular breadbins with long boards from after the C64C introduction are rare, but do exist. Some early C64Cs also have the assy 250466 long board inside.
If you are not afraid to use your zif64 VIC2 chip in an unknown machine you could take another socket and stack it so it's higher and the heat sink doesn't bump into that metal cage or whatever that's around the VIC2.
Congrats dude! Hopefully the SID stays working, both of mine had the same filter die after a couple days of use. Ended up just getting some FPGASIDs And before anyone asks, PSU has been rebuilt and SID chips were well heatsunk with big chipset heatsinks
Not uncommon for Commodore to mix and match IC manufacturers; probably to save costs! My store-bought C16 had an assortment of MOS, TI, Fairchild, and Signetics 74xx series logic chips -- (they're all TI now).
I think its about time to fit an esd mat to your work desk, these old chips don't like static at all. As chips get harder to obtain the more you need to protect the environment they are moved about in. Just my $0.02 worth as it makes my inner engineer shout no! As you pull them out. Still like to see computers younger than my PET 4016 being fixed. As I jumped from the pet to pc's due to working on custom embedded systems.
Edit 20:09 fixed. The white heat sink compound on the VIC chip R8, it spreads onto the pins. Could it be shorting out the pins/ or altering incoming signals due to some conductivity? Or the opposite, could it cause the pins not to make a good connection to the test socket?
Did you ever took a closer look at the date code of the chips in your dead chip bin to see if there is a correlation between production date and chip type? especially with the c64 chips like PLA, SID - some production badge more prone to fail than others?
