Looking at Commodore 64 Boards on a Snowy Afternoon
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- Опубликовано: 10 сен 2024
- Come on and hang out with me at the lab and we go through a pile of NTSC Commodore 64 boards, test them, and pull out a PAL Commodore 64 to compare.
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Yep the 326298 boards are the only ones that do not use the RF modulator to generate composite video, all other boards require something there to output any video. As you already figured, the 326298 boards have poor video out and it is not helped by the ceramic R56A VIC-II.
Commodore also made a mess of the 326298 reset circuit and ended up connecting reset directly to the output of the 556 timer. As the 556 output can sink 200mA, carts like the Kung Fu Flash and EF³ are unable to adequately pull reset low and the machine will usually crash.
I made a video last year on how to correct those issues, and a couple more with these boards. The one thing I didn't cover was a potential issue with the SID filter caps at C10 and C11. Some boards have 2200pF caps there, they should be 470pF. You may want to check that if you're planning on using the 326298 board for your SID comparison video.
Great info. Thanks Mark! Writing all that down since I'm probably going to do a followup video to this one.
Commodore repair videos are always welcome! Sounds like a perfect second channel video.
I really liked the casual repair vibe of the video, I think it's a great use of the 2nd channel and I hope you do more. Your new lab is very cool and it's just nice to "hang-out" in it, esp on a cosy snowy day! Looking forward to your SID replacementathon video, good luck!
Noel, I literally went through this last week myself! On the early rev A 326298 NTSC boards with horrendous picture, try swapping resistor R10 near the VIC with a 120 ohm resistor. If yours is like mine was which had a 300 ohm resistor from the factory, you'll be blown away by the improvement in brightness & color! It saved my sole C64 from ending up on eBay and being replaced with a later revision lol. (Credit goes to the C64 forums - not me!)
This is great! I'm so glad you were able to make this video with those parts.
Nice video. Never enough 64 repairs:) and ya, those earlier boards will always have a bad image. The 6567r56a vicII have horrible video... however even if you put a standard R8 or R9 in those older boards... it doesn't really help the image. 425 boards ntsc are stock without vicII cage same as the 466 boards:) no signal at all on those 2 boards is often the 8701 clock generator, or the vicII itself. Anyways long live the 64s. Thanks for sharing 👍
Love the unscripted, hang out with Noel vibe !
That Blue C64 looks sweet! Nice work, Noel!
The 425 w/o metal case on the vic is stock. Also exists in pal.
Yeah, so I've been told. It's not one I had ran into before. Interesting. I think that makes it more likely to be able to be repaired. Yay.
Yes, my 250425 PAL has no metal case, it has that round black component hanging out in the corner instead. All the big chips and clock generator was in sockets from factory I think.
Noel, On the Very Early 5-Pin Din Video C64 326298 NTSC boards, There exists a few bugs. The first is a Video bug that is fixable. Commodore in their infinite wisdom accidentally installed the wrong value resistor in the R10 location on the board. The incorrect resistor that was installed at the factory was only 120 ohms across R10. To easily make the fix, You need to install a 220 ohm resistor "piggybacked" onto the already incorrect 120 ohms resistor. This makes the fix and bring the weak video signal from the 6567 up to where it belongs. - as per Ray Carlsen. Noel, The 2nd issue is with the 326298 boards is that they have very Buggy Version 1 Kernal Roms. They need to be brought up to the latest Version 3 Kernal Rom that has all the fixes. Even Version 2 is buggy too!, hence Version 3. :) The 3rd thing is that as you already mentioned in your Video, The earlier 6567 VIC II Video chips (Gold Line and Gold Pins are not as good as a later revision 6567 VIC II Video Chips so a later 6567 VIC II chip swap may be in order.. Finally, It has been widely reported that the Kung Fu Flash has issues with these Early 326298 5-Pin DIN boards...so your issues are not at all uncommon. If you make all the fixes that I mentioned above, Your Kung Fu Flash might work correctly... Let's see! :) - Tony K. - Melbourne, FL (Commodore Collector/Restorer) Glad to see you in the U.S. ! Looks like we need a Part II Video here! Take it easy Noel! Been watching you for years! - Longtime Viewer! :)
Old revision also needs the reset and restore circuit repaired for the kung fu flash, easyflash, etc to work properly. In addition to the respairs to the video circuit mentioned below by others.
I really enjoyed this video! It's by far more relaxed than the Z80 video I watched last on the main channel.
You made me curious.. I'm no expert on the early boards, so I had to try something. This is a 326298. Which had the ceramic chip in it . I just put in a vicII kawari mini, and the video looks excellent. Crazy.. my fastload cart works in it, but not my maniac mansion cart.. strange. But anyways I had to mention that mention that :)
There was a high level of suspense here ! 33:13
Haha, tell me about it! I was WTF is happening here? But we've all been through dumb stuff like that.
18:10 - yeah, the struggle is real... 🤣 ... just seing myself there... 🙃
A DEAD TEST cartridge really will help.
Don't worry about getting the LED connector backwards. It will work either way.
Nice video, Neil. Very laid back. I've made that mistake reversing the SID and PLA and fried a potentially good PLA with 12v. Did that on a livestream so lots of people got to see me do it. 🤮The R56A VIC-II's in a couple of your boards are notorious for bad video like that. They are, in fact, so different from the R8 and R9 that if you want to use c0pperdragons LumaCode VIC-II-dizer to get HDMI through an RGBtoHDMI, you have to request a different firmware be flashed onto the VIC-II-dizer when you order from him. Hopefully you have an ArmSID in that box of SID replacements. Lots of folks, including me, consider that one the best. It's not 100% as good as a real SID, but it's the closest. IMHO.
Nice video! I only just now found this channel. Your regular videos are so concisely edited nowadays that you've removed the process, the journey so to speak. They are great high-potency sources of information, but I also like this more "rambling" style.
Perhaps it makes sense to divide the content in this way-one group of videos edited down to individual frames with elaborate annotations and overlays, the other not edited at all. Either way it's always good to see you again.
Nice chilled out video! Enjoyed it a lot 👍👍
Massachusetts! Good to hear
big fan of this, very chill
Technically, I liked all videos of this channel.
It is a known fact that early revision VIC-II's have inferior video, but I am not sure if they are this bad. If you are intending to build yourself a good working NTSC C64 out of these options, use the board with the 8701 clock generator (the one that has less parts in the VIC-II can, with the plastic cased VIC-II and the SID socket at top).
I found instructions to fix that awhile ago from someone on the Backbit forum to sort out the Reset circuit issue you are having with the Kung Fu Flash on the 326298 board (it is also with any other cartridge with a reset button). It involves adding a 1k Resistor at R36 and lifting Pin 9 of the 556, but keep the factory Jumper Wire in the hole for Pin9.. In theory you can cut the Pin9 leg from the 556. After desoldering the 556 and reinstalling it without Pin9 in making connection, I found it wouldn't work any longer. I expect it was damaged from shorting the output to ground with the Reset Button on my Final Cartridge III. Maybe it was heat from desoldering the 556, although I haven't otherwise had an ic seem to fail due to desoldering it certainly may have happened. I had seen other options for modifying the Reset circuit, but that was the easiest and it was non destructive ( provided you desolder Pin9 instead of cutting it from the 556.
Ray Carlsen has it listed that R10 was fitted with a 300 Ohm resistor, and should have a 120 Ohm resistor. He recommended adding a 220 Ohm in Parallel to the 300 Ohm, which should take it to about 127 Ohms. That will improve the video a bit. But the old Vic I am sure is a lot of the poor video output.
TheRetroChannel mentioned the RF Module is not used for Composite on the 326298 board, it could be removed and still have Composite Video out.
The board also doesn't have Chroma Luma out as an option, that can be hacked in, I haven't found instructions how to do that. I have seen two boards with that modification my 326298 and one that Adrian had shown in his Digital Basement. It is an old mod, and mine looks to be done the same way as his. It may even have been done by Commodore when they had old boards laying around and wanted to get as many out the door as they could. I don't have a "stock" 326298 to compare to my modified board to be able to tell if anything but the connector, the cut traces, and the couple bodge wires are the only changes to it. If you want pictures of the board, I could get some to you if you wanted to look at possibly adding Chroma Luma to one of the boards. It is a bit destructive, as it does take drilling a couple holes and cutting a couple traces.
My 326298 works with the Kung Fu Flash (and other cartridges that use Reset), the video is about as good as my other later model C64s. It has a later Vic chip, and R10 sorted. I use it with SVideo / Chroma Luma output that looks very good on it. It is my primary C64.
Your C64 acts like an early one, my 5 pin silver label C64 has video like this. They were never known for good video quality even on composite. No luma/chroma on them. I suspect the RF modulator is crap.
The same stupid and dangerous exchange of IC positioning is also a thing in atari 8bit machines.
On European 65ΧΕs POKEY is on the top (compared to PLA) while on 130XEs Pokey rests below the PIA chip.
I have never seen a red border on the Dead Test. Is that some special version ?
Yeah, If you ever need to boost your youtube ad revenue, Just post more Commodore/Atari/TI repair videos! People never get sick of them. I know I sure don't! :) - Tony K., Melbourne, Florida
Definitely would be keen to see some repair videos here
C64 colors are weird anyway!