NintariBoi Posted December 22, 2018 Share Posted December 22, 2018 So, I recently got a Commodore 64 from one of my neighbors along with a 1541 disk drive, Commodore 1701 monitor, and I found a psu for it at a local vintage video game store. I tested the psu and the 9v and the 5v lines are working. So, I plugged it in the Commodore 64 and turned it on. The LED did not turn on and the screen was a solid black color. I took a look inside and everything looked visually okay. So, next I poked around with my multimeter and found only 1 volt on the cassette port. I know the 5 volt line makes it to the board because I measured the voltage on the power switch and the input and output voltages were 5 volts. So, I let it sit for about 3-4 minutes and then checked the voltage again. For some reason, the on board voltage was at a healthy 5 volts, but the screen remained a solid black color. I don't know what to do at this point. Could it be a bad capacitor, chip, voltage regulator, or something else? --Other info-- Board Revision: B Using RF output for the display Z key missing Thank you. Quote Link to comment Share on other sites More sharing options...
carlsson Posted December 22, 2018 Share Posted December 22, 2018 One of the absolutely most common faults on those, besides a malfunctioning power supply, is that PLA chip which acts like a memory controller is broken. You can get reprogrammed parts or modern replacement solutions like PLAnkton, realPLA and a bunch more. However I'm not sure if a broken PLA chip would give symptoms such as voltage drops. Quote Link to comment Share on other sites More sharing options...
NintariBoi Posted December 22, 2018 Author Share Posted December 22, 2018 Okay, thank you! I'll look into getting a new PLA chip! Quote Link to comment Share on other sites More sharing options...
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