The strange case of the Commodore 64 colour bands.

[stephen_usher]

Well, if this ( https://github.com/c0pperdragon/C64-Vid ... nalog_only ) board doesn't work then doing any other conversion wouldn't as the signal from the VIC-II would be bad.

[rubber_jonnie]

Just checking, I have lost track a bit, but does yours have a 74LS193 for the colour clock at U30? If so what was the output like, did it work ok with the new crystal?

Also, what does the power supply to the modulator look like? It says 9v unregulated on the schematic, is it ok?

[mrbombermillzy]

@stephen_usher I agree. I was thinking more along the lines of 'while the board is out on the testbench, get it done' type of thing.

Would be interested to see the signal quality with the conversion done.

EDIT: I've got a Amiga DCTV composite to RGB converter and the output on a 1084 is pretty good.

[stephen_usher]

Just checking, I have lost track a bit, but does yours have a 74LS193 for the colour clock at U30? If so what was the output like, did it work ok with the new crystal?

Also, what does the power supply to the modulator look like? It says 9v unregulated on the schematic, is it ok?

Yes, it's the version with the 74LS193. The output of that clock looks fine. The 9V is fine too.

I was wondering about replacing the LM75xx regulators with buck converters, which would reduce heat, but I'm not sure how much that might help things over all.

[rubber_jonnie]

Just checking, I have lost track a bit, but does yours have a 74LS193 for the colour clock at U30? If so what was the output like, did it work ok with the new crystal?

Also, what does the power supply to the modulator look like? It says 9v unregulated on the schematic, is it ok?

Yes, it's the version with the 74LS193. The output of that clock looks fine. The 9V is fine too.

I was wondering about replacing the LM75xx regulators with buck converters, which would reduce heat, but I'm not sure how much that might help things over all.

I can't imagine the regulators getting warm would do it, like you say there is just so little between the VIC-II and the modulator, just ferrite beads, so surely it must be the modulator that's the issue.

[stephen_usher]

It was interesting that changing the crystal and capacitor helped decrease the colouration for a short time though. Very strange.

[rubber_jonnie]

It was interesting that changing the crystal and capacitor helped decrease the colouration for a short time though. Very strange.

Yeah, it's been a bit of a peculiar issue this one. Out of curiosity, are the ferrite beads damaged at all?

[stephen_usher]

Well, that's interesting. It's actually made it worse!

The colour banding is still there and it's over sharpened and the interlaced lines no-longer line up. I'm going to have to put the modulator back and think about what to replace... probably the 74LS chips in the clock circuit.

[rubber_jonnie]

Well, that's interesting. It's actually made it worse!

The colour banding is still there and it's over sharpened and the interlaced lines no-longer line up. I'm going to have to put the modulator back and think about what to replace... probably the 74LS chips in the clock circuit.

74LS replacement is always something easy to do, definitely worth a try.

[stephen_usher]

The beads are pristine. I'll have a look at the circuit to see which chips to replace.