• Please review our updated Terms and Rules here

c64 trouble...

M

marioplayr

Member
Joined
Nov 1, 2009
Messages
27
Location
grand blanc, MI (USA)
i just got a c64 at a yard sale and the guy that sold it said it worked. i got home pluged it in, and it didnt work. the guy also threw in a sega master system that didnt work, an atari 2600 that didnt have any if the hook ups and a game boy pocket that was missing the screen. i saw his add on craigslist and the place was an hour away but we were going to that area that day but the guy knew that i was 12 and got my money from mowing lawns and he riped me off. if you guys can give me some tips to try out on it or tell me where i can get another for cheap (that works:D) that would be great! thanks!!!

-marioplayr
 
describe to us the symptoms of the broken C64 and we may have an answer to the problem. just hope you're good with a soldering iron.
 
Did you get a Disk Drive as well?How about any Cartridges?(They plug in on the back)It's going to be sorta hard to use without those.
cgrape2
 
well, it just shows a black or some times grey screen. if you keep the on/off switch on and unplug the power from the system and plug it back in with the on/off switch still on, it just showes jibberish... at the bottem it has MMprogram then to the upper right hand side of that it has 012345678 written. every thime you do it it changes colors. it came with a floppy disk drive and a vicmodem. it also has a cassette for the vicmodem but no power suply for the floppy disk drive or cassette drive for the vicmodem software. it also came with a commodore 64c that was taken apart. oh and one more thing it came with is a floppydisk that was called skate rock. on the lable of skate rock it has something written about it being a commodore opperating program. i dont know what its all about but like i said, it dosnt go to the blue screen that it should. thanks for trying to help!!!

-marioplayr
 
marioplayr said:
if you keep the on/off switch on and unplug the power from the system and plug it back in with the on/off switch still on, it just showes jibberish...
Click to expand...

You probably don't want to keep doing that.
It's a good way to break the machine.
So far, you've been lucky to get away with it.

at the bottem it has MMprogram then to the upper right hand side of that it has 012345678 written. every thime you do it it changes colors.
Click to expand...

Does that MMprogram appear on the screen?
Maybe you have some sort of cartridge plugged in.
In which case, the C64 seems to work.

Andy
 
Open it up and see if the 6526 CIA chips (left side towards the User Port on the back) are socketed. If they are, swap them around and see if she'll boot.

If it wont then I'd suggest replacing the PLA chip first as that's the most common problem point on the machine.

Right now I'm out of stock on them and am waiting on my connection to bring me more machines.

How much money do you have sunk into it at this point? The reason I ask is that I do flat rate repairs on the C64 main board for $29.95 plus shipping.
 
i dont have any cartridges and MMprogram is at the bottom center. so far i spent 40 bucks on the whole heap and there was a guy with a ton of software that i was going to buy and he may have an exta c64 lying around he said and he would check to see if it worked for me and he would throw it in for an extra five to ten dollars. also what do you mean by socketed channelmaniac?
 
Socketed means the chips are in sockets, instead of soldered directly into the board.
Socketed chips can be swapped easily. Soldered chips, not so much.

Andy
 
the 6526chips are soldered in. i cant find the pal chip but there is one by a big silver block with holes in it that says:
- uA 7812
- Fuc8409
- KOREA
that chip has a hole in the center and looks like it shold have a screw in it. does that have anything to do with the problem? also when you turn it on, after about a minut it starts to smell like burning electronics... is that normal? im just checking because thats kinda wierd.....
 
No, if you smell that a chip has been likely blown or a capacitor leaking. If you update your location in the profile CP you may find someone nearby who can help trouble shoot.
 
marioplayr said:
do you know where i can get a PLA chip? electrinic store? ebay? also, do you know how much a PLA chip would be?
Click to expand...

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.

http://www.arcadecomponents.com/catalog/item/3054735/2582640.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/projects/pla-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.
 
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 (R8) and 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:
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.

marioplayr said:
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.....
Click to expand...
 
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...
 
You must log in or register to reply here.
Back
Top