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Oldschool80skid

Commodore 64 Black Screen

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Hello,

If this has already been discussed then please re-direct. I could not find any topics regarding this issue. I just connected my C64 and powered it up. At first everything was fine, but within a few minutes the screen went black. There is still power, so I assume one of the chips went bad. Does anyone in this forum fix Commodore 64s?

Thanks,

Tom

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First up: blame power supply. It is responsible for oh about 90% of all problems with C64. The 5v rail has a tendacy to go bad and dump a lot more than 5v into C64, frying everything. If it's the early black brick, I'd pitch it and get a nice replacement PSU.

 

A quick and easy way if you have Atari 2600 or NES, and an USB hub with external power. Use the 2600 or NES adapter (which does 9-10v AC) into the 2 inputs for AC power. The USB hub with external power are usually 5v 2A+, use that in the 5v pin. If you're not good with electronics, better buy a good safe one instead.

 

Second: When it's working fine for a few minutes then going black could be bad power supply, loose chips, or bad chips. Open the C64 and reseat all socketed chips (including VIA under the metal shield) and try again. If you have used good working PSU and have tried reseating but nothing works, then while the case is open and power is on, touch every IC. Anything that feels too hot (burns your finger) could be bad chip. A can of compressed air with the straw attachment, turned upside down, and aimed at the offending chip give it a quick squirt. If your C64 works while it's chilled, replace the chip.

 

Third: I'd suggest a trip to lemon64 forum, there are experts there that can probably pinpoint your issue more quickly than I can.

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First up: blame power supply. It is responsible for oh about 90% of all problems with C64. The 5v rail has a tendacy to go bad and dump a lot more than 5v into C64, frying everything. If it's the early black brick, I'd pitch it and get a nice replacement PSU.

 

A quick and easy way if you have Atari 2600 or NES, and an USB hub with external power. Use the 2600 or NES adapter (which does 9-10v AC) into the 2 inputs for AC power. The USB hub with external power are usually 5v 2A+, use that in the 5v pin. If you're not good with electronics, better buy a good safe one instead.

 

Second: When it's working fine for a few minutes then going black could be bad power supply, loose chips, or bad chips. Open the C64 and reseat all socketed chips (including VIA under the metal shield) and try again. If you have used good working PSU and have tried reseating but nothing works, then while the case is open and power is on, touch every IC. Anything that feels too hot (burns your finger) could be bad chip. A can of compressed air with the straw attachment, turned upside down, and aimed at the offending chip give it a quick squirt. If your C64 works while it's chilled, replace the chip.

 

Third: I'd suggest a trip to lemon64 forum, there are experts there that can probably pinpoint your issue more quickly than I can.

Thanks Uzumaki. I pressed all the chips which seem pretty well seated and checked them for overheating. Non of them felt extremely hot based on touch. Unfortunately I do not own a USB hub with external power. I will check out the lemon64 forum as suggested.

Thanks,

Tom

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I do repairs, but the PS needs tested as well.. If the PS is still good, I'd recommend one of Ray Carlsen's power savers, or as stated above, a better PS. You can get a good older one that's Commodore brand by looking for a PS that came with the 1764 RAM expansion (tough to find) to a c-128 PS - you can either add the correct din plug yourself (the 128 has a square plug), or get the adapter cable on eBay. Not the cheapest options, but these types of PS' don't die and fry stuff like the old brick style ones do.. Don't be fooled by the tan ones that look just like the black bricks- they are just 64c ones that will kill your 64.

 

The black screen is the toughest one to troubleshoot- it can be RAM, PLA,VIC II, CPU, along with almost anything else. That's where a working socketed test board comes in handy..

Edited by TheRealAnubis

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I do repairs, but the PS needs tested as well.. If the PS is still good, I'd recommend one of Ray Carlsen's power savers, or as stated above, a better PS. You can get a good older one that's Commodore brand by looking for a PS that came with the 1764 RAM expansion (tough to find) to a c-128 PS - you can either add the correct din plug yourself (the 128 has a square plug), or get the adapter cable on eBay. Not the cheapest options, but these types of PS' don't die and fry stuff like the old brick style ones do.. Don't be fooled by the tan ones that look just like the black bricks- they are just 64c ones that will kill your 64.

The black screen is the toughest one to troubleshoot- it can be RAM, PLA,VIC II, CPU, along with almost anything else. That's where a working socketed test board comes in handy..

Ray fixed my C64 and she is working like new. :)
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Hello All,

First post to this part of Atariage because I am a TI'99er first and foremost.

However, I enjoy all vintage computers/gaming machines and have 2 C64 computers.

One is an SX64 and works just fine. The other is a 64C and does not - black screen.

 

I have plugged in a kickman cartridge and get the screen attached here.

 

post-39776-0-69096500-1431185235_thumb.jpg

 

I have opened the computer up and I reseated the chips - no change.

I did a touch test and found u10 and u22 (ram) too hot to touch - replaced the ram chip in u10 (socketed) and could not in u22(not socketed)

Somebody must have been in the computer before, right?

Anyway, Do you think replacing the hot u22 ram will fix the issue and get the computer to work properly?

Thanks for any tips you might be able to give me.

-Ralph...

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Hello All,

First post to this part of Atariage because I am a TI'99er first and foremost.

However, I enjoy all vintage computers/gaming machines and have 2 C64 computers.

One is an SX64 and works just fine. The other is a 64C and does not - black screen.

 

I have plugged in a kickman cartridge and get the screen attached here.

 

attachicon.gifc64c.jpg

 

I have opened the computer up and I reseated the chips - no change.

I did a touch test and found u10 and u22 (ram) too hot to touch - replaced the ram chip in u10 (socketed) and could not in u22(not socketed)

Somebody must have been in the computer before, right?

Anyway, Do you think replacing the hot u22 ram will fix the issue and get the computer to work properly?

Thanks for any tips you might be able to give me.

-Ralph...

 

Hi, there are many causes for a blank screen on the Commodore 64. It's possible that bad RAM is your issue, but it could be something else as well. The Kickman cartridge is what's called an "Ultimax" cartridge. These can sometimes give you an indication of a failure because they bypass certain components like RAM and ROMs.

 

Some people have luck testing for failing RAM by putting a known good chip on top of the old. But a good indication of a failed RAM is it becoming really hot like you've stated.

 

I would also check your power supply. If you are using an original "brick" type of power supply, I'd get rid of it as soon as I could and find a modern replacement. They are the cause of a lot of failures in the Commodore 64.

 

Check out this link of a former service tech for Commodore: http://personalpages.tds.net/~rcarlsen/cbm/c64/

 

Lots of good information there to help you troubleshoot the issue yourself. He also still does repairs as well.

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Thanks for the info sm3.

I'm fearful of removing the hot chip because the traces are so damn tiny. Wish I could find somebody who repairs c64's here in Phoenix. If I place a good ram on top of the hot one it might give an indication of the issue?

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Thanks for the info sm3.

I'm fearful of removing the hot chip because the traces are so damn tiny. Wish I could find somebody who repairs c64's here in Phoenix. If I place a good ram on top of the hot one it might give an indication of the issue?

 

That guy I linked above, he lives in the state of Washington. I've sent items for repair to him and I've also purchased items from him (power supplies). He doesn't charge all that much (for repairs) and is someone you can trust.

 

You might want to just email him and ask your tech questions directly.

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Yes, I have had repairs done by Ray Carlsen on a few of my VIC-20's and he is not only a great, respectable guy, but a true Commodore genius! I recommend him very highly!

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A black screen and garbage screen can also be caused by a bad CIA. I believe CIA#2 has two control lines which control bank switching for the VIC-II.

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Thanks guys

The computer is going to be boxed up and shipped to Ray this weekend for him to work his magic on. Those traces for the hot ram chip are too tiny and delicate for my weary old eyes. Plus if the ram ain't the issue it will be in the hands of a guy who can fix it.

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Thanks guys

The computer is going to be boxed up and shipped to Ray this weekend for him to work his magic on. Those traces for the hot ram chip are too tiny and delicate for my weary old eyes. Plus if the ram ain't the issue it will be in the hands of a guy who can fix it.

 

I wouldn't be surprised if he repairs and mails it back to you on the same day. He works really quickly!

 

It takes longer for the packages to arrive at his place than actual repair time.

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If the Ram is hot, then it is the issue, at least one of them anyway.

 

Make sure Your c64 power supply is good otherwise Your nice fixed c64 will die again.

Hopefully You shipped the power supply too..

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I asked Ray about sending the ps along and he said I wouldn't need to because he has designed a protection circuit that he installs that will keep a bad ps from cooking chips. All I had to send was the motherboard. I'm hoping its just that hot ram but you never know.

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If you are using an original "brick" power supply, I would ask Ray to purchase one of his "64 savers". It's a device that keeps your original brick power supply from killing your 64 *when* it fails.

 

He also sells new power supplies (switching type) but they are not too cheap. If you are serious about using a 64 you might want to invest in one. If you do go that route, you will not need the "64 saver". I have 2 of them myself and they work great!

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I asked Ray if I should send the ps along with the motherboard and he said no need because he will be putting a saver on the motherboard as part of the repair. So if my ps is the likely killer the saver will protect it this time around.

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