The PLA chip is near the 6581 and is typically labeled 906114-01 or 82S100
RJ
The PLA chip is near the 6581 and is typically labeled 906114-01 or 82S100
RJ
I think PLA also.
do you know where i can get a PLA chip? electrinic store? ebay? also, do you know how much a PLA chip would be?
The PLA stands for Programmable Logic Array. It is similar in purpose to a PAL or GAL chip. This chip is used for a lot of the glue logic in the C-64 in order to reduce parts count. Unless you have access to a device programmer, you'll need a pre-programmed one.Originally Posted by marioplayr
http://www.arcadecomponents.com/cata...35/2582640.htm
Looks like they're out of stock though.
Here's some info about the PLA. Looks like you could use an 82S100 as a replacement part and use the programming file included:
http://www.zimmers.net/cbmpics/cbm/c64/pla.txt
Sounds as though those are hard to come by, which would require taking the original equations and compiling for another device (and fabricating an adapter board, since most PLDs are a different form factor).
At one point a while back there was talk of replacing the PLA with an EEPROM, since most available now are much faster and serve basically the same purpose. Some info on this page:
http://mikenaberezny.com/hardware/pr...a-replacement/
A more practical solution for you unless you have access to a device programmer will be to get a donor C-64 or one from a donor system from someone on here or eBay.
I have about a half dozen of them that I haven't listed on my site yet (site shows out of stock). If memory serves me right, they are $8.99ea.
http://www.arcadecomponents.com is my site.
sorry i have not posted anything lately. its because i kinda gave up on the commodore but i decided to hook it up one more time to see what was going on with it. i hooked it up and on the screen, it showed a black outline=, sometimes red or blue, and a red or blue box in the middle that said, "1234567890-=qwertyuiop[]\asdfghjkl;'zxcvbnm,./1234567890-=qwertyuiop[]\asdfghjkl;'zxcvbnm,./" over and over again! it just writes everything that's on the key board in like red or blue. do you guys still think its the pla chip?
-marioplayr
I'm not sure if I've understood, but this C64 have a blown 7812 chip.
If yes, try to replace it, because this 12V are used not only by the cass motor, but it's the second voltage for the VIC II (video chip) and the SID (sound chip). Without regulation, it's likely to supply this chips with 17V.
The failure is very strange. Could you upload a screenshot ?
Have you got a cartridge working with this C64 ?. A BASIC cartridge for example ...
Appart from PLA and CIAS, check the U15 (74LS139). This chip serves to the addressing as well as the PLA. Because it selects, CIAS, VIC and SID, a failure there would produce weird effects. The last C64 I fixed have this IC broken.
Garbage screen (multicolor) is a RAM sympthom. Either the RAM itself, of the multiplexers U25 and U13 could be the problem.
I'll give a try to the kernal and basic ROMS too. I know they are hard to find. The best way to fix a 64 is with a working C64.
I have one acting as a benchmark (a PAL-N Drean Commodore) and some spare chips ...
I was lucky,. I fixed 4 c64 and never replaced a custom MOS chip. Two cases were RAM and two glue logic IC's.
Anyway I have 1 PLA, a ROM set (225,226 and 227), 3 CIAS, 2 6502,1 6581 and 1 NTSC VICII (Rand many glue logic to fix any future C64 I'll buy =).
i cant upload a picture but i just bought another c64. the guy let me see it running and it came with a TONE of software, 2 c64s, a 1541 disk drive, and a printer. it all worked but then the disk drive keeps saying that it cant read the floppy because there is no data on them. it said online that it needed to be realigned but i don't know how to do that. i have the disk for it. oh and one more thing, the one messed up c64 was fried, one of the manuals diagnosed that in the trouble shooting guide... so can anybody help me with the disk drive now?
edit-oh and two questions:
1:my disk drive has a flap that you turn down... not the switch in the middle.... would that be a newer model or an unusual 1541 drive?
2:i got two commodore 64s... right? they are both c64s, not commodore 64c. one has normal brown and gray keys. the other has white keys and light gray function keys. whats up with that? oh and the guy said he bought it like that. he didn't put new keys or 64c keys in it.....
Last edited by marioplayr; February 21st, 2010 at 07:17 AM.
There's a good thread about the 1541 rigth here.
The 1541 get lost very easy with reading errors. By get lost I mean that the head was driven to a half track (by firmware error). Once the head is over a half track the disk drive cannot read the track position anymore. Any attemp to disk access will fail, even if you turn on and off the drive.
To force the 1541 to get reference bumping at track zero type on the C64:
open15,8,15
print#15,"I"
close15
Quite common solution .. it's listed in the owner manual of the 1541 !!!!!
The typical sympthom is that the drive worked fine until a disk error occurred. Then, the drive won't work, even with proven good disks. If it happened to you, this commands will help.
Avoid doing this very often. The 1541 get out of alligment easy.
I think that the one mecha with the tab in the center (ALPS mecha) is earlier that the one which has the lever (MITSUMI mecha).
I alligned my brother's 1541 with ALPS mecha the previous week, and it's the same as the mitsumi one. The head cleaning is a bit difficult in the ALPS.
Also bougth a 1571 drive. I love the 1541 look, it has THE C64 "look", but the 1571 is better product by far, less reading errors !!!!
About the messed 64, you can fix it anyway.
ok, so i tried doing the hole open, print, close thing but nothing happened. all it did was made a machine gun noise and then said ready befor i got to type close15. also, the red error light was flashing after i typed print#15,"I". do i do this with a disk in it or with out? do i try to load the disk then do all the commands (the open, print, close commands), just do the commands, or do the commands then try to load the disk? i still cant get the thing to run...
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