| Posted By
Anoyd
on 2003-10-18
|  Plus4 stopped working
Hey, I bought my second plus 4 from ebay two days ago. I got home powered up, and it worked!! So I sat down and played it for about two hours solid. This morning I turned it on and played again for roughly two hours. But, while being chased by Long John Silver, I turned into a pile of white mush and the Plus 4 hung. After a reset all I can get is a black screen on the tv, I read the other posts and it was suggested the TED chip may be dead, or the 8501. Does it sound like this could be a similar thing? The thing that gets me is that I was finally hopeful I'd found a working plus 4, and for £20 too. Darn!
Any help is appreciated,
Graham
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Posted By
JamesC
on 2003-10-18
| Re: Plus4 stopped working
If the unit works again after cooling down, then suspect a bad power supply. If it still does not work after cooling for several hours, THEN suspect problems inside the computer itself.
You see all those round blue things and brownish canister-like things on the motherboard? Those tend to go bad with NON-use. Ideally a Commodore computer would be powered on all the time, but if a unit is to be 'stored' then a better idea is to rotate among your existing units; use one for a month then put it away and use another for a month, etc. This way you spread the wear out among several units, and each one gets some use and some wear, instead of one unit being used constantly (causing wear on the chips from power on/power off) and the others not being used (ruining all those blue and brown thingys).
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Posted By
Anoyd
on 2003-10-19
| Re: Plus4 stopped working
I tried it again today - I got garbled mush within the text space and the blue border appeared, it then went back to a black screen after i powered off and on again. I'll try the powerpack from the other plus 4. Assuming it is the chips on the mobo, does anyone have a map of the motherboard identifying which is which? I assume the 8501 is the chip under the metal grate, and the bank of chips is the RAM, but i'm unsure as to the rest.
Cheers,
Graham
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Posted By
JamesC
on 2003-10-19
| Re: Plus4 stopped working
Sheesh I was really tired last night.... errors all around from me. Ulysses was correct in pointing out that the TED is a 7360 or 8360, not a 7501/8501. And I got the colors backwards on the motherboard resistors and capacitors.
Anyway the TED is in the metal cage and it's marked 7360 or 8360. The 7501 or 8501 processor will be just to the right of that cage. Just to the right of the processor is a 6551; that's the onboard communications chip for the user port. Yes the RAM bank is those small chips in the bottom right corner.
You could also have a problem with the BASIC or Kernal chips, those are U25 and U26 just below the TED's cage. Might also be the PLA, I believe that's the chip in U19. The PLA is the programmable logic chip. It's socketed on the Plus/4 'cause the 64's early production had a lot of those go bad, and the 64's were soldered to the motherboard. By socketing the chip it is field repairable instead of sending the whole motherboard back to Commodore.
One place we know the problem is NOT, and that's the 3+1 software in U23 and U24. Even if those are inserted in the wrong order, or missing completely, the computer will still come on to BASIC.
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Posted By
JamesC
on 2003-10-19
| Re: Plus4 stopped working
Another correction --- U23 is BASIC, U24 is Kernal, U25 and U26 are 3+1.
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Posted By
Anoyd
on 2003-10-22
| Re: Plus4 stopped working
Thanks for the info man - I'm gonna try the other psu this weekend, hopefully thats it but I'm not too hopeful :S
I'll let you know how I get on
Cheers
Graham
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