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Posted By

Imperious
on 2014-05-17
10:01:39

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

I have seen that Spanish site a few weeks ago, unfortunately there isn't enough information given out to build that circuit. No schematic and the photo is too low a resolution to read the chip names.

There was another called 65028501 which was the one I tried. Not really sure why it didn't work, maybe too many wires causing noise. The one on the Spanish site wouldn't fit in a plus/4 anyway, too big.

Only way to do this in a plus/4 is to do a double decker board with 6522 on the lower and 6502 on the upper part, but might be able to squeeze it in 1 board if I use a 6510. I will try again in a few weeks hopefully.

I have 3 plus/4's, 2 work perfectly, one has a dodgy cpu that gives the "Break" error. I swapped a good 8501 in which proved that was the fault.

Posted By

kopsec
on 2014-05-17
04:18:39

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

Most of 8 bit computers are quite easy to repair, just need chip swapping, reseating or deep cleaning.

If you have a difficult fault not solved with this, then it is time consuming to repair, but if you have the knoweledge and the schematic it's only a matter of time. If you are doing as a hobby then you spend all the time you have until fixed. Intermitent faults are the more dificult

Appart from the odd TED or CPU all the other chips and TTL logic are easy to find and very cheap.

I have now 2 C16 boards not working, but they need 2 CPUs and 1 TED, but I have 2 perfect working ones. When I have time enough I will try to fix this 2 boards, in the meantime they can serve as spares for the 2 working ones.

Imperious have a look to this forum in Spanish, they managed to make the 8501 CPU from a board using 65C02 cpu

http://www.retrowiki.es/fororw/viewtopic.php?f=687&t=28683&sid=4e676b64222a2a2556f25bfa306cdc8b&start=10

I had to buy the 8501 for my C16 on ebay germany, it was the CSG CPU that runs cooler:

http://www.ebay.de/itm/MOS-Commodore-8501-Prozessor-CPU-2MHz-DIP40-/231186294448?pt=Bauteile&hash=item35d3c6e6b0

Ask the seller for shipping cost if the price is OK for you.

Posted By

MIK
on 2014-05-16
07:22:40

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

We used to have PET's a school, but because of the limited nature of them at the time they were quickly replaced by BBC Micro's. The PET's remained in the corner of our Maths room not being used right up to spring of 1987 when I left the school. The BBC's were great for one thing, it introduced me to a game called Thrust! I so wanted it to be released on our platform. My prayers were answered a couple of years later though!
Thrust is one of my most sacred games on our system, it's worth nothing and is cheap to buy when it shows up but the fact it was ever ported at a time when I had given up hope makes it special in more ways than one, and it's the version I enjoy the most!

As for claims of dead machines and people giving up on them, they obviously don't have a clue what they are doing. Very rare your ever find such talk in these parts and this is the longest running C16/Plus4 website where people could talk to each other via a forum. That would be most peoples first port of call, find any site that is all about the machine.

There is even a guy on ebay.co.uk that will fix C64, C16/Plus4's, Vic20 ect... for a fixed price so if people have given up they should send them to him. Where there's a will there's a way.

PS. Some of us I'm sure are starting to worry about you in general, negative stuff as if you may suffer from some anxiety disorder? I would be the first to admit I do but don't want to be reminded of it by someone else haha! Enjoy what you have and worry about if and when any machine dies when it happens. Having spares saves the hassle there and then, work on fixing the faulty machines afterwards! Limits the need to worry.

Posted By

Retro76
on 2014-05-16
01:15:28

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

Thanks For Sharing Guys

I hear what you are saying MIK that we all need the occasional black machine to provide the spares to keep our machines going....Hooray for preservation

. But unfortunately i see too many people claiming that the machines are totally dead & have given up way too easily on trying to fix them

. In all my years i have never seen a PET CBM in person & only saw one on the bay sell for around 800AUD in non-working condition. They are definitely ultra-rare here and i would never personally consider purchasing one as there is no way of knowing if i could ever get it to work and i believe this intermittent problem was common amongst electronic equipment in the 70's & early 80's. For the novice, finding the internal short on such machines may take weeks, months or years & as Crock says ' not a cost effective use of time'. Botched repairs are definitely a real problem as can be seen on soldering diagrams containing cold, bad joints & damaged traces/mainboards.
I guess pinpointing any complex problem can be like looking for a needle in a haystack; that is if you can first find the haystack LOL

I was actually thinking about corrosion & mould so im glad you brought that up Imperious !
I guess if either of the two but particularly corrosion were to creep up on the layers of your machines you would be in serious trouble

I have seen this happen on many others computers from battery corrosion but luckily for the plus4 world this cannot happen

YES the day will come when someone can readily produce reliable fpga 8501 & TED replacements.....but at least you gave it a real-shot (Thumbs Up) Gotta get Csabo to add some more smiley piccy's !!!

Posted By

Imperious
on 2014-05-15
04:01:00

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

The only thing apart from being physically cracked that kills Motherboards beyond repair is corrosion between the layers. That would be more of a problem with 3 layers and up though, not the 2 layers that these 8 bit Commodores have.

I have recently sourced 2 TED chips from ebay via UTSOURCE, unfortunately only 1 of them worked, they sent a replacement that worked though. I then bought 5 from another chinese supplier, 3 worked, they are supposed to be sending me 2 replacements. I would be amazed if they both work.
What I cannot find though is 8501 Cpu's, they are all gone, although You never know if some more might crop up at a later date. I tried making up the 6502 replacement but It wouldn't work even though my wiring was all good. I am going to try later with a 6510 and see how that goes, less 74ls chips required for that.

I also got 10 (rare as hens teeth) VIC 6561-101 chips, all of them tested perfectly in my Vic-20 which gives You an idea of how crappy the 8501 and 8360 chips are as far as longevity goes, with the 8501 being worse than the TED in my opinion.
Would be fantastic if someone came up with a fpga 8501 and TED replacement, I definitely do not have the skills for that.

Posted By

crock
on 2014-05-15
02:24:05

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

To date, I've never had a 264 machine that I could not find the problem on. As far as I can recall the only 8-bit Commodore that I have completely failed on is an 8032 PET which has an intermittent fault and blows fuses (I suspect there is an internal short in one of the soldered components.)

The most difficult cases are usually where someone has botched an attempted repair themselves. I fixed a couple of 64 boards last year where someone had tried to remove a couple of chips and the modulator and had then resorted to brute force, pulling out many via's (links between the bottom and top of the board) and tracks in the process. Took hours to repair and certainly not a cost effective use of my time but, as with many people in this hobby, I'm a bit obsessive/compulsive when it comes to fixing them.

That's not to say that they are all working. For every 3 working machines, I probably have 1 which is a donor and missing many components.

Posted By

MIK
on 2014-05-14
23:58:47

Re: When Are The Plus/4 Family Of Computers Considered To Be Dead ?

You see the odd chip for sell now and then and what there is is aimed at people who might of bought a broken machine and just need a chip or two. Some one might of even bought a known faulty machine but just wanted a white keyboard, what's left over is moved on if people can be bothered to do so. It saves buying a whole machine just for spare parts... It's nothing to worry about as working machines are available all the time and in fact it can be helpful to some people out there, those people that are more then likely going to use the computer once it's running.

Most can be fixed from a pure chip change which is the good part. The odd and rare proper dead ones which would be mother board related where knowledge of what your looking at and soldering skills would be required are few and far between. Good on those who can fix them is all I can say!

I have one that's faulty beyond a chip change. The keyboard was given away to a freind of a freind, remaining & working chips taken out to fix others I have that are in perfect working order thanks to it and because I have enough spares to last ages, that faulty board can just stay there in the box of spares doing nothing. I'm sure I have enough to keep me going before my time is up and long before I ever get to the point I need to get this one faulty board fixed.

I'm even unwilling to let go of the faulty TED that I damaged via the joyports using a Sega Megadrive pad purely because it works for the most part... Well it has life any way and that's enough if I ever need it one day, but in reality I would do anything possible to have a perfect working machine rather than make do and use it haha! That's what hoarding is all about, or I like to call it preserving.

Posted By

Retro76
on 2014-05-14
05:49:00

When Are The Plus/4 Family Of Computers Considered To Be Dead ?

Hey Chaps

This one has been bugging me for a long-time. There are many people out there who claim that there black/grey computer(s) are dead & they hastily strip all the parts & sell them online (What a waste if you ask me

)
As far as i know all the chips & cpu are replaceable as well as the capacitors & other circuits.
Power supply's are easily replaced or fixable

, so what could totally kill off a computer ?

The only thing i can think of is a broken mainboard. Traces on a MB are also repairable as well as cold joints from past soldering. Missing keys from the keyboard can still get you by as well as changing fuses & wires.
I would really like to know if the real pros like Crock, Kopsec & Imperious have ever had a computer which they could not repair ? Im sure others would have interesting things to say as well, so let the posts begin