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Re: The strange case of the Commodore 64 colour bands.
Posted: 03 May 2022 21:17
by stephen_usher
Oh well, after warming up it went back to the original banding. Oh well.
Well, it can't be anything to do with the oscillator or the VIC-II. That leaves the 74LS629 or later in the circuit, in the modulator.
Well, when I replace the modulator with a by-pass board:
https://videogameperfection.com/product ... eo-bypass/
Re: The strange case of the Commodore 64 colour bands.
Posted: 03 May 2022 22:53
by rubber_jonnie
stephen_usher wrote: 03 May 2022 21:17
Oh well, after warming up it went back to the original banding. Oh well.
Well, it can't be anything to do with the oscillator or the VIC-II. That leaves the 74LS629 or later in the circuit, in the modulator.
Well, when I replace the modulator with a by-pass board:
https://videogameperfection.com/product ... eo-bypass/
Oh, that's rubbish :(
I know how you feel after my my 600XL shenanigans, getting ready to reassemble and finding out the problem can back after a while. It was my own fault though for not correctly disabling the original 3.5Mhz oscillator properly.
I guess it doesn't leave a lot to try any more.
Re: The strange case of the Commodore 64 colour bands.
Posted: 06 May 2022 10:35
by stephen_usher
It looks like the modulator replacement board *may* arrive on Monday.
Re: The strange case of the Commodore 64 colour bands.
Posted: 06 May 2022 11:54
by rubber_jonnie
stephen_usher wrote: 06 May 2022 10:35
It looks like the modulator replacement board *may* arrive on Monday.
Reminds me I need to fix my VIC-20 modulator. Just for kicks as the composite out is really quite nice.
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 13:39
by stephen_usher
The C64 modulator replacement board has arrived, so all go for trying it tonight.
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 13:44
by mrbombermillzy
For goodness sake. This MUST be the last thing left to try. Fingers crossed. :)
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 14:44
by stephen_usher
It is as far as I can see. There are merely a couple of ferrite bead links and ceramic caps (from what I remember) between the VIC-II and the modulator and that's it!
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 14:48
by rubber_jonnie
stephen_usher wrote: 09 May 2022 13:39
The C64 modulator replacement board has arrived, so all go for trying it tonight.
Fingers all crossed for you!!
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 15:33
by stephen_usher
Yeah, me too. Actually, other than the ferrite links there's nothing between the VIC-II and the modulator and nothing between the modulator and socket so if this doesn't fix things then nothing will.
I'm wondering if I could replace the UHF output using an Astec UM1286 modulator, tapping the composite and audio signals from the new board. That would give the best of both worlds.
Re: The strange case of the Commodore 64 colour bands.
Posted: 09 May 2022 15:43
by mrbombermillzy
If there's any more mucking about to be done after this, I would be tempted to do an RGB conversion of the signal (like the French/SECAM C64s had).
https://www-c64--wiki-de.translate.goog ... r_hl=en-GB
https://www-c64--wiki-de.translate.goog ... r_hl=en-GB