Commodore 64 RF Video Issue Help

[INTVCruise]

Hello everyone, I just had a quick question. I purchased an untested C64 for parts cheaply and when I received it I was surprised that everything seemed to function just fine on it. The only problem is that when I test it using a converted C128 to C64 power supply, after about 7-8 minutes there is an invisible line that appears in the center of the video feed and it starts getting more and more wavy and scrolls, the lines look like an ocean for example. I'm not sure what you call that, I think v-sync? Anyways, with the Ray Carlson power supply I have I tested the unit and it does not seem to occur even after testing with it for about 30 minutes. Lines never seem to get wavy but I haven't tested any longer than that. Could the problem be with the computer itself or could it be the C128 power supply is getting old and is having trouble supplying enough power to the unit. I couldn't test the other monitor port because it only has 5 pins not more like some of the other C64 models. The power supply works just fine on my other C64 with different monitor out ports, so not sure if there is some other differences with this C64 that require less power than the other? Thanks for your help! 

[INTVCruise]

3 hours ago, INTVCruise said:

Hello everyone, I just had a quick question. I purchased an untested C64 for parts cheaply and when I received it I was surprised that everything seemed to function just fine on it. The only problem is that when I test it using a converted C128 to C64 power supply, after about 7-8 minutes there is an invisible line that appears in the center of the video feed and it starts getting more and more wavy and scrolls, the lines look like an ocean for example. I'm not sure what you call that, I think v-sync? Anyways, with the Ray Carlson power supply I have I tested the unit and it does not seem to occur even after testing with it for about 30 minutes. Lines never seem to get wavy but I haven't tested any longer than that. Could the problem be with the computer itself or could it be the C128 power supply is getting old and is having trouble supplying enough power to the unit. I couldn't test the other monitor port because it only has 5 pins not more like some of the other C64 models. The power supply works just fine on my other C64 with different monitor out ports, so not sure if there is some other differences with this C64 that require less power than the other? Thanks for your help! 

Also one other question, I had a dead C128 power supply that wasn't working because I suspected the fuse was blown, which it was and replacing it with another from a different C128 PSU made it work again like normal. The fuse I pulled put that was non-functional was marked Buss, which I assume is the company name, AGC 1 6/10 and 250V. Is the 1 6/10 the Amps the fuse is rated for? Sorry if it's a dumb question haha. Also, does anyone know where I can get that exact match. Thanks. 

[Markeno]

If it is 5 pin video, then it is the early model such as a 326298 board like my one C64.  I expect the internal 5Volt 7805 regulator is overheating.  They have a horribly inadequate heatsink.  It will be made even worse if the 9V AC input is higher because that is what it works with.  It is even possible the heatskink came off or came loose making poor contact with the 7805.

 

My 326298 had a very small heatskink riveted to the 7805, it was loose and not making good contact.  It was also not enough of a heatsink for the task.  I think some of those may even have been shown to have no heatsink.   A modern replacement supply may very well have a higher 9V AC input to handle more current such as the 128, this is not a big deal on the later boards that have a much larger heatsink on the internal 7805.  I have 2 new supplies, one with a bit higher AC so I keep that with my later board and the lower one with my 326298.  I also put a larger heatsink on the 7805 in it.

[Markeno]

On 12/15/2020 at 6:49 PM, INTVCruise said:

Also one other question, I had a dead C128 power supply that wasn't working because I suspected the fuse was blown, which it was and replacing it with another from a different C128 PSU made it work again like normal. The fuse I pulled put that was non-functional was marked Buss, which I assume is the company name, AGC 1 6/10 and 250V. Is the 1 6/10 the Amps the fuse is rated for? Sorry if it's a dumb question haha. Also, does anyone know where I can get that exact match. Thanks. 

Standard 1.6Amp 250Volt Fuse.  I think probably Fast Acting, not slow blow.  I wasn't sure either what the 1 6/10 exactly was, I pulled up the power supply schematic and it lists a 1.6Amp Fuse.