C64

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Revision as of 07:06, 26 December 2019 by H3g3m0n (talk | contribs) (→‎Repair)
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  • Black PSU - 5.1v/10.3v - 5.13v/10.40v
  • White PSU - 5.15v/10.2v - 5.19v10.43v

Dead Drive

Dead C64

VIC-II

RF Mod

TODO

  • Black Screen. Pulses monitor/pops when turned on.
  • Power supply seems ok (5.18v). Fuse replaced (I managed to blow it while poking around with the multimeter :/)
  • Nothing shows up when toggling on and of rapidly (PLA check).
  • Disk drive spins up when turning on.
  • Load "$",8 does nothing (not sure the disk drive is working, had to replace a capacitor). Tried poke commands to make sound without success.
  • Check VIC-II Vcc is 5v. pin 40 is 5v
  • you're looking for the RESET line to be grounded for half a second during powerup. Pin 3 of userport. RST line goes high after half a sec (and stays high)
  • No ram chips over heat. Only hotish chip is 6510
  • Clock in on 6510 (pin 1) *seems* to be toggling (unsure, multimeter measures it lower than 5v but not ground).
  • Clock out from 6510 seems to be stuck at 5v
  • Address lines 0-11, seem to be under 5v but not GND. Except for pin 12, 13, 14, 15 which are 5v.
  • Can I use Chroma/Luma on a composite monitor (ie for just black & white image)?

PLA

Dead Monitor(s)

Power Switch

Games

https://www.youtube.com/channel/UCnhr67lnXf3ZtcKLrr9-hSA/videos


Repair

I'm trying to repair my C64. It is a PAL, ASY 250425

It black screens.

  • I have tried a deadtest cart but it still blackscreens.
  • The power supply is under 5.2v.
  • The voltage regulators on the board are outputting the right voltages.
  • The reset line stays low then goes high after a few secs.
  • I have replaced the PLA with a PLAnkton.
  • Replaced the VIC-II with a new one.
  • Replaced the clock generator with a TOLB (I'm fairly sure I broke the original while poking the crystal with a multimeter :/).
  • Removed the SID
  • Removed one of the CIA's (the other is socketed)
  • I am getting 984.9 Khz clock in and out on the 6010.
  • There is activity on the CPU's datapins.

I have tried using poke commands to generate sound without success. Also tried to make the disk drive do something via load (but I'm not %100 sure the drive is working). Is there something I can do with the tape drive?

None of the chips feel particularly hot (The VIC-II's get a bit hot but afaik thats normal).

I don't have another C64 to swap things with. I have a multimeter+freq checker. A logic probe. (No Oscilloscope).

My current next possibilities is to either: Remove the M1 RF Modulator and replace it with a hand built one. Remove the other CIA and the ROM chips and try the deadtest cart again (Since it doesn't need them). Remove all the ram chips and test them with an Arduino.

TODO

  • Diagnostic guide RAM Check...
  • Replace CIA and try typing poke commands again...
  • Remove more chips...

http://retro64.altervista.org/blog/commodore-64-repair-a-quick-guide-on-the-steps-required-to-fix-it/