Closed C64C (PAL)

[Plimsol]

Hi all,

I'm on a retro drive and I don't have a working C64, and of course regretting selling mine all those years ago when I moved on to the Amiga.

I''m after a C64C in good working condition with tape drive, power pack and leads. Not too bothered about box or joystick/games although a few would be nice.

cheers
Marios

 

[Chinners]

PM (about to be) Sent

 

[Merlin]

@ Plimsol

Welcome to Amibay!!

I might be wrong here, but does "I don't have a working C64" mean you actually have a broken one, or haven't got one at all?

If you have a broken one, we may be able to help you fix it.

 

[Plimsol]

@Merlin

Thanks!

Yeah I do have a broken bread bin. Power light comes on but can't get a picture via RF and datasette doesn't get power. I recall it broke shortly after I got it a few years ago, think I may have stupidly pushed/pulled a game cart with the power on.

Haven't looked into repair, not sure if it's worth it...

---------- Post added at 22:08 ---------- Previous post was at 22:05 ----------

PM'd Jasey, he's sorted me out

 

[Merlin]

Well, I may be in a position to help you...

Is your SID chip on the main board the 6581, the one in a socket? If so, I have a spare 'breadbin' main board without a SID that you can have for the postage.

It works, or at least it did until I donated the SID to TheCorfiot for his C128 restoration.

PM me if you want it with your deets and I'll work out the postage. I can't say fairer than that. It's not all about Miggies on here, ya know.....



Edit: if you are sorted out, would you ship the knackered bread bin to me, so I can fix it?

 

[Plimsol]

I'll have to open it up and take a look - I haven't even tried giving it a dust off yet . How can I open up the case without damaging it too much?

Jase has agreed to let me see if mine is fixable first so I'll check it out. If I can't do anything I'll be happy to send it over.

 

[Merlin]

OK. Opening a breadbin C64 is dead easy. There are three screws underneath at the front. Remove those, then hold the unit together as you turn it over. Lift the top of the case at the front so that it sort-of 'hinges' at the back (there are locating lugs at the back), then as you lift the top, unplug the keyboard plug from the main board at the left and the power LED from the right of the board and the top should be off.

There are tabs that hold the cardboard screening in place and this comes off easily.

I would start by carefully removing all of the chips that are socketed one at a time, clean the legs and make sure that they are firmly replaced in their sockets. They tend to 'creep' out of the sockets over time and this may be why it's not working. I've seen quite a few revived by re-seating the chips.

Good Luck.

 

[Plimsol]

thanks Merlin, I'll let you know how I get on

 

[tokyoracer]

If it's really dusty i'd suggest getting a hoover and that thin attachment and get rid of it all so you have a clean (ish) work area. That way you should be able to identify the chips more.
Just make sure you don't touch or scrpe the hoover bit on the motherboard.

 

[Plimsol]

@Merlin

so I tried as suggested and removed and replaced the chips which are removable but no joy . The board itself isn't dusty and everything looks well set and still intact, including the big fuse.

Are there any other obvious things I could check out?

 

[jvdbossc]

My bet is Kernal rom chip.. Mesure the voltage..Check the cable connection somethimes the power supply connector has a pin pushed in.. Be happy to have a unit with the sockets, there quite easy... If you really wan't it going you'll source a working unit, so you can source a rom switcher with the C64 kernal and jiffydos etc.. (available here and there)

 

[shem]

Hi everyone
I have been away from this forum for a while but being a commodore enthusiast I thought I would try to shed some light on the subject.

Going back to the faulty bredbin do you get nothing on your tv or do you get a black screen ?

The original bredbin machines have one fatal problem when the video is just a black screen 90% of the time and that is the PLA marked U18 ( marked 906114 or earlier versions have a 82s100 ) on the board but it could also be a one of the rom chips a 6526 a shorted sid or bad ram

PLA chips are harder and harder to get hold of as that is the most common problem with the early grey c64's
If you are looking to repair this board here is a link to a guide

http://personalpages.tds.net/~rcarlsen/cbm/c64-ic.txt

If it is a blank screen it could be a number of chips and the last thing you need is to start looking for spares and change things at random

It could also be bad/shorted ram chips
these are marked on the board as 4164 or 4264 and there will be in two rows of 4
I guess its a little harder to diagnose the problem in a forum without doing some checking on the actual unit

Also see if one of the ram chips get hot they should not if they do they are bad
most ram problems are caused by a bad psu as commodore in their wisdom decided to fill the old psu's with epoxy resin to stop them from making an irritating buzz given off by the transformer after a while the psu components cant breathe and overheat


other things to try is to remove the sid (U17 6581 )the machine will still power up without it but you will get no sound not that it matters as we are looking for video not audio right now

you can also remove U1 ( 6526 ) leftmost chip near the keyboard connector you machine will still display commodore basic xxxxxx bytes free etc but without U1 you will not have a cursor

If Merlin's board is good and it will power up with the sid missing get that from him or if you really wan the board working i would be happy to fix it for you


Hope this helps
shem...

 

[Plimsol]

seems to be that there is nothing appearing on the tv, no black screen and none of the chips are running hot

so i used a multimeter for the first time in a long time and tried measuring the PSU. DC comes in at 4.94V but AC is 1.2V on each, which doesn't sound right. Unfortunately I don't have a spare PSU to compare with.

Can't say I'm too keen to start removing chips, and without any spares sounds like it might be a forlorn effort. I think I may just write this off and ship this off to someone who can maybe revive it...Merlin you interested?

 

[jvdbossc]

I am quite sure you don't need the 9V to get the rom screen, I think only sound and some expansions need it at all, so not the right suspect, I believe..

Did you switch the multimeter properly to AC?

 

[Merlin]

Can't say I'm too keen to start removing chips, and without any spares sounds like it might be a forlorn effort. I think I may just write this off and ship this off to someone who can maybe revive it...Merlin you interested?

Yeah, OK dude. I'll PM you some deets tomorrow and if you let me know the postage costs, I'll cover them.

 

[shem]

Well according to the schematic

the old style 64 ( breadbin ) with the 6569 vic chip does need the 9 volt that's is what powers your rf modulator
the 12 volt dc is derived from the 9 volt ac and powers the sid and the vic chip ( pin 13 )

the 9 volt also powers the casette motor and the user port
so without the 9 volt you will not power the vic the sid and modulator so you will not get any video or audio

here is a link to part of the schematic for a bread bin
look at the modulator section pin 1 marked +B

http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/251138-1of2.gif

the newer boards ( c64c ) on the other hand will give you video as the newer vic chip and modulator require only 5 volt
if it is an old board and you got no 9v ac you will need another psu

hope this clears things up

 

[Plimsol]

thanks everyone for the tips. I'm hanging on to the broken one for now so that when I come across another power pack I can try it out. Is a C64C PSU is compatible?

Speaking of C64Cs, my original post still stands - does anyone have one they would be willing to sell? I PM'd Jasey about his but he seems to be AWOL...

 

[StrontiumDog]

Speaking of C64Cs, my original post still stands - does anyone have one they would be willing to sell? I PM'd Jasey about his but he seems to be AWOL...

https://www.amibay.com/showthread.php?t=6516

 

[Plimsol]

@blankstare

thanks, yeah that's a nice setup no doubt

But a bit more than I need, I'm happy with a bog standard unit + leads with datasette in good working order

 

[StrontiumDog]

It does say I'll split the package if asked lol