C64 issues

[relaxo]

after many years i recently setup my old c64 and discovered it is somewhat faulty.

when i first turned it on i got the regular startup screen, except that some of the characters were either missing or flickering. i could load games from tape reasonably reliably, though of course the graphics were largely corrupted. i was unable to load anything from disc - the 1541 chugs away for a few seconds before reporting a read error. i found my old Final Cartridge and tried plugging it in to see if i still got flickering/corrupt/missing characters but not a whole lot happened, apart from the c64's symptoms changed: now the characters are all there and no longer flicker (yay!) but they're all black (boo):



which means when i load up any games 99% of the screen is black. (the fact that it changed after plugging in the cart makes me nervous).

after doing some googling, it seems it may be due to a few issues (maybe the PLA?) but the symptoms don't completely match the descriptions i found. as a side note, sound & music seems fine so i don't think it's the SID.

so now i'm wondering what my options are. i've never done any kind of computer repair/restoration, so i'm doubtful i'll be capable of conducting even remotely complicated surgery. is there any place in NZ that handles repairs of old machines? are there any reasonably simple things i can try to narrow down the cause?

also, as i mentioned, i haven't been able to load anything from the 1541. i'm guessing this is due to alignment issues, but i'm not sure. i know there was an old application which assisted with drive alignment, but i'm pretty sure i don't have it (and if i did i wouldn't be able to load it). is there any point in trying to fiddle with the alignment if i don't have that application?

[tezza]

also, as i mentioned, i haven't been able to load anything from the 1541. i'm guessing this is due to alignment issues, but i'm not sure. i know there was an old application which assisted with drive alignment, but i'm pretty sure i don't have it (and if i did i wouldn't be able to load it). is there any point in trying to fiddle with the alignment if i don't have that application?

You might have checked already but don't discount deteriorating disks. Or dirty heads. Or the latter caused by the former. Even one disk with flaking media can coat the drive heads after just a rotation or two. The drive won't read any disk from then on and might even damage them.

[matsondawson]

I would wonder if it's a poor connection, maybe some of that freeze spray would expose it if it was.

[relaxo]

apologies for the silly questions, but am i able to check/clean the 1541 heads? i had been wondering if it might be the disks - i tried a couple of dozen, all with the same result, but they've all been stored in the same place.

and how would i go about trying out the freeze spray?

[Carcenomy]

Sounds like you have a bum PLA. This is not what I would consider uncommon in the 64...

[relaxo]

yeah i recently picked up a couple of C64Cs and one is a straight black screen while the other has flickering text.. so i guess the latter may be PLA again, not sure about the former. i wasn't too surprised by this (as you say, not uncommon), but i was disappointed by the 2 1541-II drives being borked, i.e. when trying to load from disk they both just make the typical 1541 grinding sound and refuse to read any disks.

my old 1541 seems to at least make more of an effort - with the "new" two they make the same sound whether or not a disk has actually been inserted.. so i'm wondering if there is something more obvious wrong with them. of course, it's hard to say whether it's the disks or the drives. i've tried a load of disks (originals and copies), none of which have worked.

[kevman3d]

i've never done any kind of computer repair/restoration, so i'm doubtful i'll be capable of conducting even remotely complicated surgery. is there any place in NZ that handles repairs of old machines? are there any reasonably simple things i can try to narrow down the cause?

Sounds like my dilemna at the moment - Hacking my way (probably not the best choice of words) through a ZX Spectrum in an attempt to bring them back to glorious life. Right now, I'm kinda working through one of them - the trick is to try and dig around for information... And unlike myself, find a pile of broken old electronics - buy a soldering iron - and practise. I went straight in - I was panicing that I'd fry something so just didn't hold the iron on long enough to properly melt the solder - I did manage to scorch the PCB a little, and it was kinda stressful (even more after I toasted a finger tip). But the satisfaction of learning something about these things, replacing a component and watching it still power up (even though it still had the same problem) was empowering in a way.

But I definitely know where you're coming from. This is the last thing I wanted to do, but I decided for what I paid only $10 for, I'd go for it nonetheless in the hope I can repair it - that said, even at that price, I really don't want to damage it if I can avoid it (its a piece of history, not a piece of junk afterall). What I'm learning from this one I hope to transfer across to the other as well (and do it better now I've learnt a lot more about the process and techniques). Ideally I would like to get both running - but if I can get at least one going, even if I have to borrow parts from one to get the other running, I'll be chuffed.

Anyway... Here's a little bit of stuff that you may find worth looking at...

A quick video about checking the PLA on a machine with a black screen - Why this guy is shirtless I've no idea, but its got a few tips (if you can understand his accent).
http://youtu.be/MdOWm5M0LL4


As for some fault diagnosis and solutions, this has a few common fault and repair descriptions:
http://www.faime.demon.co.uk/retro/cbm.html


Interesting list of common problems for C64s in terms of chips, etc
http://www.zimmers.net/anonftp/pub/cbm/ ... ng-c64.txt


And a similiar one on diagnosing/common problems for the C64c
http://personalpages.tds.net/~rcarlsen/ ... 4cdiag.txt


Just Google "C64 Repair" - you'll find loads of stuff. Those were just a few that I ran into in the first 5 minutes. I prefer to find videos if I can - often seeing what someone does is easier to follow then trying to decipher some electronic expert tell you what rails and pins to test... And then doing it wrong anyway.

[relaxo]

thanks for the great info! i'm sorry about taking so long to reply - life got in the way and the spare room continues to be littered with the c64s, monitors, broken joysticks, and all the other bits and bobs i dragged out but haven't managed to do anything with. i'm hoping to address this over the next few weeks.

it's encouraging to hear you started out in a very similar place! i'm sure there will be a few casualties when i get around to soldering, but as you say, it's a good thing i have a broken machine (or two) to start with.

as far as soldering, de-soldering and so on goes do you have any thoughts on the equipment one needs? i'll be totally starting from scratch so i'll need to start looking around for a soldering iron etc.

[kevman3d]

it's encouraging to hear you started out in a very similar place! i'm sure there will be a few casualties when i get around to soldering, but as you say, it's a good thing i have a broken machine (or two) to start with.

Haha! I'm still in that same place, just less stressed and a little more confident about doing things...

As for gear - obviously the guys here on this site have a lot more advice (and experience) then me, but If you're like me (A complete noob)

Jaycar has a complete starter kit for around $44 (includes the iron, solder sucker, small multimeter, etc) - Check it out...
http://jaycar.co.nz/productView.asp?ID=TS1652&CATID=74&form=CAT2&SUBCATID=953#1

Desoldering wick is handy (http://www.surplustronics.co.nz/products/4043-desoldering-wire)- it absorbs solder (like a wirey-sponge ) - from what I've seen in online tutorials (I've not used it that much, well, at all - I do have a reel of it) it won't remove solder from the holes in the board (due to surface tension of the molten solder) which makes it primarily a clean-up tool for when you make a mess on the PCB itself. It'll be handy at some point I'm sure...

Definitely try and get some Flux fluid. http://www.mindkits.co.nz/store/tools/Liquid-Flux-Pen-Water-Soluble

Interestingly, most flux seems to come in "pen" form from what I found. It basically looks like a highlighter that dispences flux liquid rather then whiteboard ink. Something new - all I wanted was a small bottle of it, but it'll do... You'll need this to help solder flow easily over wires, components, etc. If you don't, like me you'll get frustrated as solder collects and beads on the tip of the soldering iron and won't come off nicely... Note on that point - you need a damp sponge as well to wipe the tip of the iron on... Make sure that your wife doesn't see you using the one she cleans the cats food bowl with...

Copper wire is another handy resource. If you need copper wire (just in case you need to fix something, or in my case, add wires to fit some modern transistors that are too large (and have different pins)) - an old ethernet cable is a good thing to have. Its loaded with handy thin wires - and lots of it.

A magnifying glass and clips - without this, it was causing me so many headaches. I was trying to solder and watching things slip and slide out of my hand made me wonder how the heck anybody did this stuff... (and led to me melting my skin a little when the iron slipped, plus it was a headache with my eye sight not being able to see the small details). Having something to hold your components in place really helps... If you want a cheap place to buy this stuff, SurplusTronics has great prices on a lot of gear (I just bought a soldering stand for $6.50 the other day). In fact, they have better prices then Jaycar on many things. I was kinda bummed that I spent $15 on one at JayCar, and they have a similiar one at Surplustronics for $8.50:

http://www.surplustronics.co.nz/products/5082-helping-hands-tt0052

One last thing I got (but you won't need it in 99% of cases) was some heatshrink tubing. For components with metal surfaces, or for wires you want to prevent from shorting out things that they may touch, its valuable... Put it over your component/wire/etc and use a hair dryer to shrink it tight. I need it for my transistors as they're metal, and they'll just sit on top of the PCB and zap the crap outta things.

This does remind me that I have to get back to finishing up some work on my ZX Speccies... Just needed that flux to get some copper wire to bond to a transistor leg, but obviously haven't had time in the last couple of weeks to do it.

[kevman3d]

Some handy tutorials for soldering, etc... I need to watch/read a few more of these myself... But worth a look:

Soldering surface mounted components (ie. chips soldered to the PCB, etc)
https://www.sparkfun.com/tutorials/36

This guy fixes ZX Spectrums, but he has a great video showing how to solder/desolder components. Great video, very easy to understand
http://youtu.be/u_NnU48bmv4

He has a couple of other videos. I picked up a few pointers from him in his youtube channel.

Mark Fixes Stuff is a lot of fun, but inbetween the odd crass british humour, there's a few tidbits - such as understanding what is a "Dry" solder joint.
http://youtu.be/9VYA9ufb4Jc

Great video explaining what and how to use a Multimeter:
http://youtu.be/Uhkq_9eufbM

Do a search on Youtube and you'll find loads of great tutorials for electronics... Obviously I haven't spent a lot of time watching everything, but I'm feeling a lot more confident once I got over my "don't touch the soldering iron on the circuit or you'll melt it" mentality. Its kinda daunting - but watching others on youtube really makes it look easier... Just go play with old circuits first to get some practise... Soldering your precious machines can scare you something silly if you don't (which is what I did - but didn't seem to break anything so I guess I was lucky).

Good luck...

[relaxo]

thanks so much for all that great info! very much appreciated.

progress has been slow.. i lost the use of the spare room for a few weeks, but have now reclaimed it finally got a bench to work on and have managed to somewhat organise the mess of machines, monitors, broken joysticks, cables and floppies (so many floppies...). next step is to crack on with picking up some soldering equipment - all a lot less daunting now thanks to your posts.

[kevman3d]

No worries... Right now I've tweaked one speccy with no luck unfortunately. I'm going to make a start on the same repairs on the second one and see if it will make any difference... Crossing all the fingers and toes...

Another couple of tips from what I've picked up so far:

• If you're going to have to remove something from the PCB (specially one that's 20+ years old) its worth melting BOTH sides of the solder join (top and bottom of PCB) a little before unsoldering and pulling the part off. When I pulled out some transistor legs (I melted the solder from the bottom of the board while I pulled the leg out from the top with a pair of needle-nose pliers) I noted that while they came out easily, the solder was still in a solid clump where it had been sitting in the hole all these years. I guess I was lucky it didn't damage anything...
• Solder suckers have plastic tips - and at first I didn't want to touch anything hot with it - but the only real way to get the solder to remove is to push it close against both the PCB and the soldering iron tip. The plastic seems to be more heat-resistant then I thought. I spotted someone online doing it, tried it, and it made a huge difference.
• The other way I was sucking solder was holding the PCB up on its edge using clips, then placing the sucker on one side of the board, the iron on the other. Worked as well... But then there is the odd chance an old PCB might be damaged if the tracks/pads come off with the suction as well.
• And make sure after sucking solder, you put the sucker to one side and press the plunger to eject the molten solder. I'd also check the circuit board to make sure it hasn't splattered onto it. It should theoretically flake off, but so far I've not had that problem.

Good luck - hope you manage to try some of that stuff out and get a positive result...