C64

• The 6510 and the 8500 from the later boards are interchangable, you can replace one with the other.

• http://www.linusakesson.net/scene/lunatico/misc.php
• http://www.linusakesson.net/programming/poems-for-bugs/index.php
• http://www.aaronbell.com/secret-colours-of-the-commodore-64/
• https://www.metafilter.com/114704/Demoscene-The-Art-of-the-Algorithms
• https://digitalerr0r.net/2011/04/30/commodore-64-programming-6-raster-interrupts/
• https://csdb.dk/forums/?roomid=11

• Supermon Overview

• Black PSU - 5.1v/10.3v - 5.13v/10.40v
• White PSU - 5.15v/10.2v - 5.19v10.43v

• Arduino Kernel Rom
• JiffyDos DolphinDos Mod
• JaffyDos

• Remove ICs
• Heatsinks
• #11 "Zero Insertion Farce?" — Installing ZIF Sockets on a C64 Motherboard
• Sells Nordic Replays, C64 Reloaded Motherboards, SuperPLA
• EEPROMs as ROMs
• Using the USB Logic Analyzer with sigrok PulseView
• C64 Video Cables
• https://github.com/fdivitto/FabGL

Dead Drive

• https://www.lemon64.com/forum/viewtopic.php?t=64021
• https://www.youtube.com/watch?v=CDj6JEqPkzA
• C15 Capacitor

Dead C64

• Black Screen Guide
• Another Black Screen Guide
• https://www.youtube.com/watch?v=Mn1keRFXX7I
• Test Fuse
• Test for 5 volts on chips
• check +12V on pin 13 of the VIC
• 5 volts on userport
• https://github.com/jamarju/c64_test_tools
• Commodore 64: how to repair it, step by step

• Replacement PLA, local (more expensive), Alternative, cheaper from the store
• Replacement Capacitors
• #01 "A Change of Heart" — Commodore 64 Black Screen Repair
• aphexteknol
• the 250425 board should in fact boot to the familiar blue BASIC screen just fine without U1 and/or U2. (However, with U1 gone, e.g. the keyboard obviously won't work and with U2 gone, e.g. the serial port won't work).

• Chip Data
• Datasheets

VIC-II

• [1] - £23.84 (AUD$45.19)
• Commodore 64 VIC-II MOS 8565 R2 PAL video chip 5v (*TESTED*)! WRONG CHIP. Also dodgy and more expensive...

RF Mod

• I did this RF mod mod
• Removing the RF modulator on a C64 (PAL, 1983, W. Germany 251137, Rev B)

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

• http://forum.6502.org/viewtopic.php?f=8&t=3465

Dead Monitor(s)

• https://www.lemon64.com/forum/viewtopic.php?t=28565&amp%3Bstart=30
• https://gona.mactar.hu/Commodore/monitor/Commodore_monitors_by_model_number.html
• "found that CP2 has disintegrated! It`s a paper capacitor next to the power switch that has exploded, so that needs replacing.", "the x2 cap is a common failure"

Power Switch

• https://www.youtube.com/watch?v=g2lrrXp-Zn8
• http://www.retro-commodore.eu/2014/04/12/c1084-power-switch-replacement/
• https://randommayhemstuff.blogspot.com/2016/11/finally-swapped-power-switch-on.html 1084
• https://www.wagneronline.com.au/pcb-mount/switches/electronic-components/swp583-2978/347/pd/ PCB MOUNT PUSH SWITCH $11.50
• http://www.telespares.com.au/index.php?main_page=product_info&products_id=312936 (Much cheaper, not sure if the same)
• https://www.thefuturewas8bit.com/1084switch.html (OUT OF STOCK)
• https://au.element14.com/c-k-components/ne18-2a-ee-sn-p-6amp/switch-pushbutton/dp/2435346 - Maybe this is the same
• https://www.lemon64.com/forum/viewtopic.php?p=667259&sid=d8a1ae892e1436641358a9501da82ad1

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.
• Screen does 'pop' when turned on and it's a different level of 'black'. No borders. No sparkles. Just black.
• The power supply is under 5.2v.
• The voltage regulators on the board are outputting the right voltages.
• Removed the SID
• Removed one of the CIA's (the other is socketed)
• 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.
• I am getting around 984.9 Khz clock in and out on the 6010.
• There is activity on the CPU's datapins. 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 programed the CPU correctly?)
• 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. The basic stays high the entire time. With the deadtest they all stay high.

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 continiously).

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

I don't have another C64 to swap things with. I have a multimeter with freq meter. A 8ch 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

• Test Address lines...
• Remember to look at the AEC line to see if its a vic or CPU cycle.
• Also look at BA line
• Some boot information
• German stuff
• More german test points
• Manual tape control via pokes
• "if the 60Hz can be found on _IRQ (pin 3), the KERNAL was able to program the CIA timer". "IRQ has a duty cycle of 98% high (2% low)", "IRQ -> generated by the CIA, but no IRQ does not automatically mean CIA bad, with no IRQ the sytem should start w/o cursor (blink)" No 60hz...
• Check the chip select lines on the PLA.
• "verify AEC (pin 5 of the CPU) in relation to PHI0. If you don't catch a badline it looks like AEC is the same as PHI0, only slightly shifted. With a badline, AEC would be LOW all the time."
• "The _CAS signal on the VIC"
• Investigate that 'himem' bodge wire...
• 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/

• pin 21 (color clock, 17.73 MHz) and pin 22 (dot clock, 7.88MHz).
• Test Points
• _CS on the ROMs: The BASIC-ROM (901226-01) is not addressed in idle mode, but access can be produced simply by pressing the RETURN key
• The duty cycle of _CAS must be higher than that of _RAS for the DRAM to work.
• Some signs I had that the 6510 could be stuffed was a non existent BA signal and a messed up looking RW signal.

 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%

• "If you plug in a cassette tape does the motor run if you press play? If it does the computer's running, it's just something screwing up video (I had a faulty RF modulator do that to me once)"