C64: Difference between revisions

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* Checked the traces from the RAM's to the CPU datapins.
* Checked the traces from the RAM's to the CPU datapins.


I have tried using poke commands to generate sound without success. Also tried to make the disk drive do something via load with no response (but I'm not %100 sure the drive is working). Is there something I can do with the tape drive? (When I press Play it spins continuously).
I have tried using poke commands to generate sound without success. Also tried to make the disk drive do something via load with no response (but I'm not %100 sure the drive is working). Tape drive motor spins continuously when plugged in.




I don't have another C64 to swap things with.
I don't have another C64 to swap things with.
I have a multimeter with freq meter. A 8ch logic probe. (No Oscilloscope).
I have a multimeter with freq meter.
A 8ch logic analyser.
A logic probe pen.
No Oscilloscope :(


I'm not really sure where to go from here.
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.


===MISC===
===MISC===

Revision as of 13:05, 2 January 2020

  • The 6510 and the 8500 from the later boards are interchangable, you can replace one with the other.
  • 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
  • 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. No flashes, waited 30seconds.
  • I seem to get video 'sync'. No borders. No sparkles. Just black.
  • None of the chips feel particularly hot (The VIC-II's get a bit hot but afaik that's normal).
  • The power supply is under 5.2v.
  • The voltage regulators on the board are outputting the right voltages.
  • Removed the SID
  • Removed the CIA's
  • 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 :/)
  • The reset line stays low then goes high after a few secs as expected
  • I am getting around 984.9 Khz clock in and out on the 6010.
  • There is activity on the CPU's datapins and address lines. All of them are seen in both high and low states.
  • On the CPU _IRQ stays high. (This is supposed to be 60hz if the Kernal has programmed the CPU correctly?). I have tried with the CIA's socketed and without.
  • On the PLA I see CASRAM (pin17/F0) toggle on and off (it seems opposite to KERNAL). BASIC (pin 17/F1) stays high (Maybe one brief low on power), KERNAL(P16/F2) toggling on and off continuously. CHAROM(Pin15/F3) mostly high with occasional patches of low. I'm unsure if these signals are inverted.
  • On the rom chips the KERNAL's CS signal is toggling at the CPU rate. The CHAR ocasionally triggers (bad lines?). The basic stays high the entire time. With the deadtest they all stay high.
  • AEC on the 6510 toggles on/off.
  • R/W on the 6510 seems to stay high (occasional very short dips, not sure it's enough to do anything).
  • BA on the PLA stays high.
  • CAS on the PLA toggles on/off
  • Checked the traces from the RAM's to the CPU datapins.

I have tried using poke commands to generate sound without success. Also tried to make the disk drive do something via load with no response (but I'm not %100 sure the drive is working). Tape drive motor spins continuously when plugged in.

I don't have another C64 to swap things with. I have a multimeter with freq meter. A 8ch logic analyser. A logic probe pen. No Oscilloscope :(

I'm not really sure where to go from here.

MISC

  • Addresses 0-11 are connected from CPU to ROMs.

TODO

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

 Signal where?  Frequency duty cycle 
 PHI0 CPU Pin 1 985 KHz 50% 
 _IRQ CPU Pin 3 60 Hz 98% 
 _RAS VIC Pin 18 1.97 MHz 27% 
 _CAS VIC Pin 19 1.97 MHz 41% 
 Dot Clock VIC Pin 22 7.88 MHz 56% 
 Color Clock VIC Pin 21 17.73 MHz 45%
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