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C64 haul

I recently got 2 basically spotless C64's in their boxes to add to my collection. Inside they are clean as new and neither of them look as they were used much. The issue I have is both of them exhibit a black screen upon boot up. I have read that the most likely cause is a dead PLA chip seeing as they are getting power and the internal fuse checks out. I have read that since I do not have a dead test cart that if I were to plug in specific titles of cart games they might work as the games don't require some of the PLA functions to operate. Has anyone heard of this and if so it is a reliable test? Starting with the easiest forms of diagnosis would be the best method in my opinion and if I can avoid it I would rather avoid buying a dead test cart for the time being. Otherwise I will just set these aside and mess with them later after I have purchased the correct diagnostic tools.

Re: C64 haul

Jeff Stringham wrote:

> ...both of them exhibit a black screen upon boot up. I have read that the most likely cause is a dead PLA chip...

Yes, that would be the first thing I'd think about.

> ...I have read that since I do not have a dead test cart that if I were to plug in specific titles of cart games they might work as the games don't require some of the PLA
> functions to operate. Has anyone heard of this and if so it is a reliable test?

No, I've never heard of using a game cartridge to test out the PLA. I wouldn't consider this a reliable test.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

PLA

Thank you for the help! Now the second question is where to source a PLA. I know oldsoftware.com has them for about $20 each and I have bought from them before. Does that price seem fair? I am not sure what the value of these chips are currently. Any ideas of a good source or places to avoid would be of gret help to me.
Thanks again!

Re: PLA

Jeff Stringham wrote:

> I know oldsoftware.com has them for about $20 each and I have bought from them before. Does that price seem fair?

Like many of the products that are sold by that store, the price seems a bit high.

> Any ideas of a good source...

Well, one source is to pull the PLA out of another C64. Then there are the EPROM replacements -- the one from Ray Carlsen (but Ray wants the whole computer sent to him so that he can "tune" the EPROM to the particular C64), the one from Eslapion in Montreal, Canada, and the SuperPLA EPROM from Individual Computers and its distributors.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Re: PLA

I almost forgot about http://www.arcadecomponents.com They have chip pulls and NOS chips. Specifically, the PLA is at

http://www.arcadecomponents.com/catalog/item/3054735/8335676.htm

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

PLA

Thanks again for all the help! I ordered 1 PLA from the link you gave me, $14.99 for NOS seems fair enough to me. After looking again at old software they do seem to have pretty high prices. $300 + for a 64! If the prices they have were actually a good market value then I would have enough to pay rent for a good couple years haha. I guess we can dream but thats about all. If it works out well then I will have to order one for my other dead machine. Part of the fun is the hunt of finding the machines and the repair is the rest of the adventure. It is a fun experience taking something that does not work and then being able to make it work like new. I always say I could be spending my money on much worse things, this is not a bad vice to have :)

Re: PLA

:) Heh, you are a much braver man than I. If I need repairs on my Commodores, I let Ray Carlsen do them. If I need repairs on my Amigas, I let the tech at The Other Group of Amigoids do them.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Hi Robert, they aren't that
Hi Robert, they aren't that bad to replace the chips from a Commodore 64 computer. Taking them out is really easy, putting them back in is fine as long as the pins are lined up correctly. I also try to work on Video Game PCBs and those are much harder since the some of the PCBs I have had been in various climate changes so the chip legs are very brittle. Yes, I do like arcadecomponents.com as he has so many of the vintage chips and that Commodore PLA is certainly one to grab.
Re: Hi Robert, they aren't that

Well, replacing C64 chips isn't hard part (unless they are soldered in). It's the diagnosis that is more difficult. That is why I leave the more esoteric stuff to Ray Carlsen. :)

FCUG celebrating 33 years,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Hi,
Hi, First to check when you have black Screen on 2 C64s is the PSU. Did you test them with the same PSU (external power supply)? If yes, maybe this is the reason (also not very likly as it does not fail often). Also check the fuses. Also you should mention your board Revision. If it's the first board ("KU board", unlikly), capacitors are a known Problem. If it's a later board (469) a black Screen is often a Problem of the RAMs (464 type of RAM, 2 installed) Black Screen often caused by PLA on older boards (425, 407), yes. But I also got a black screen with a broken CIA 6526 one time for example (also very unlikly in your case). Maybe also RAM or ROM Problem. You can test with a cartridge at best with a so called "Max Machine" cartridge (e.g. Le Mans and other games, about 20 were released). It puts your C64 into a Max compatible mode, with only 2 kB of RAM and also "replacing" ROMs, meaning you see a picture when the ROMs are gone (as Max did had no ROMs at all, it did only start up with cartridge plugged in). But also Max had a different PLA (6703 as far as I know) it is no method to test a PLA. You can built your own PLA with an EPROM. It does work for me for booting up the C64. But it makes strange Errors like colorful chars etc. So it is not very reliable, but a cheap method of testing for your PLA Problem maybe. $14 is very cheap for PLA if it works. There are also modern replacementparts available built on CLPD Technology. Hope that helps a bit. Tell us about your test and if it works.
To me, $20 sounds fair

To me, $20 sounds like a fair price for part that has been out of production for decades! Granted there were millions of C64's sold that somebody can do chip pulls from, but I imagine most of them get trashed (or scavenged for parts) if they are not in use. (But $300 for a C64 is just silly.) More amazing is you found somebody selling NOS parts... I mean it seems hard to believe there would be any left by now...

Anyway, I agree $14 for NOS parts is a good deal.... thanks for the link!

Say, I was thinking... maybe those NOS parts were generic PLAs that were programmed for C64 compatibility? Anybody know? I mean it does sound more reasonable than a stock of genuine Commodore parts that were never used! (Of course it doesn't matter if it is 'genuine' Commodore for most people... it just needs to work!)


I'm kupo for Kupo nuts!

PLA
After testing the one unit I have confirmed that it is the PLA. I purchased one PLA to test both units with and it should be here next week. I will update as soon as I know it works. From the information on the arcadecomponents.com website they have 2 options, one is a working pull (I think it was about $8) and then the Commodore NOS chip I got for $14. I assume from the information it is a genuine Commodore part but just as long as it works I will be happy. I can say though that their customer service is awesome, I think I have found my new favorite source for parts! Looks like they have a lot of parts for many machines and the prices are much more reasonable over other places I have looked. Seems odd that there is so many parts still available but then Commodore was huge in it's day and I can imagine that they had a lot of parts left when they liquidated.
Hi everyone,
Hi everyone, Name here is Raymond and I run Arcadecomponents.com. The PLA chips are new old stock 82S100 or PLS100 PLA chips programmed with code that came directly from an 82S100 PLA from a Commodore 64 that I dumped. I sent two chips over to a Lemon64 member who tested them thoroughly with cartridge and disk games and different hardware options that he had. The code was also used by the folks to improve the MESS emulation for the C64. I've sold over 100 with no complaints of timing issues that show up with EPROM versions. I have almost 2 whole tubes of the PLS100 chips left. I'm looking around for more, but they are hard to find - unless I want to gamble with buying from China and that's a resounding HELL NO.
Call me a cheap bastard... I learned to fix things to save money... even surface mount soldering... Visit my website: http://www.arcadecomponents.com My repair logs have moved to NewLifeGames.com!!!
C64 Custom PLAs

Thanks Raymond for supporting the Commodore community!!!!  So it seems my theory was correct (wow!).  Of course feedback from the customer is the ultimate proof... he speak highly of you, so I've book-marked you (pending his confirmation).


I'm kupo for Kupo nuts!

Re: Hi everyone,

channelmaniac wrote:

> Name here is Raymond and I run Arcadecomponents.com

I like going to your site to see what you have in the way of Commodore and Amiga chips.

> The PLA chips are new old stock 82S100 or PLS100 PLA chips programmed with code that came directly from an 82S100 PLA from a Commodore 64 that I dumped.

Oh, that is interesting. We still have a FCUG member who bought 50 supposed SID chips from China, and still after many months, he hasn't tested any of them! Ray Carlsen even offered to test them for him, but he didn't take up Ray's offer.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Custom PLA
Just an update on this little project of mine. The PLA arrived today (great packaging BTW) and after installing it and plugging in my computer I was greeted with a blank screen. Thinking that this was something either more than the PLA being dead or something I messed up installing it I was somewhat disappointed. I decided to check all my cables again just to be sure and low and behold I somehow had knocked the video cable out of the back of my monitor! After reconnecting it and crossing my fingers I flipped the power switch... The screen flashed and I got the familiar Commodore Basic screen!!! It worked the first try! Everything works like it should and all of my drives and other accessories work. Now time to sit and play some games with my newly working machine! Lesson of the day- check all the connections before doing the initial test. Through great help from here, a great supplier that I think is my new go to source and some work on my end I have successfully resurrected a machine that is older than I am. Overall a good night for me!
Re: Custom PLA

Hurrah!

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Great news! :)
Great news! :) If you run across any blank 82S100 or PLS100 chips I have the code for them posted on my web site. Anyone can download it an use it. I have about 50 or so C64 boards to finish harvesting chips off of. After that they all get tested in a C64 with a diagnostic cart and loopback plugs before being posted to my site. All computers were dead and came from a defunct repair center in Texas so no live C64s were harmed. :)
Call me a cheap bastard... I learned to fix things to save money... even surface mount soldering... Visit my website: http://www.arcadecomponents.com My repair logs have moved to NewLifeGames.com!!!
Re: Great news! :)

channelmaniac wrote:

> All computers were dead and came from a defunct repair center in Texas so no live C64s were harmed. :)

Oh, what was the name of the repair center? I may have heard of it.

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

Never asked. When it was in
Never asked. When it was in full tilt I lived in the midwest.
Call me a cheap bastard... I learned to fix things to save money... even surface mount soldering... Visit my website: http://www.arcadecomponents.com My repair logs have moved to NewLifeGames.com!!!
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