exxos's Atari, Amiga & retro forum

The inductances turned up... now I have colour composite video... not very good but it works.

I've now added something the original machine never had... a reset switch. :-)

stephen_usher wrote: 02 Apr 2026 22:12 The inductances turned up... now I have colour composite video... not very good but it works.

I've now added something the original machine never had... a reset switch. :-)

How did you fit the reset out of interest.

PhilC wrote: 02 Apr 2026 22:21

stephen_usher wrote: 02 Apr 2026 22:12 The inductances turned up... now I have colour composite video... not very good but it works.

I've now added something the original machine never had... a reset switch. :-)

How did you fit the reset out of interest.

Merely short the cap in the reset circuit. It uses a cap and a high resistance connected to VCC to delay an input to a gate on a 74LS00 (from memory) which connects to the global reset line. Shorting the cap brings the line down to ground and discharges the cap. Once the switch is opened again the normal reset recharge time starts and once it gets above the TTL trigger threshold the global reset line goes high.

@stephen_usher good idea as you're using everything that's already on the board and only need the switch. I may be something similar with mine when I do the ram upgrade.

stephen_usher wrote: 02 Apr 2026 22:12 The inductances turned up... now I have colour composite video... not very good but it works.

I've now added something the original machine never had... a reset switch. :-)

Cool, any screenshots? Any idea why the visual quality is poor?

rubber_jonnie wrote: 03 Apr 2026 10:39

stephen_usher wrote: 02 Apr 2026 22:12 The inductances turned up... now I have colour composite video... not very good but it works.

I've now added something the original machine never had... a reset switch. :-)

Cool, any screenshots? Any idea why the visual quality is poor?

I think that it’s noise on the colour clock.

No pictures at the moment. I’m not at home ‘til Tuesday now.

stephen_usher wrote: 03 Apr 2026 11:57

rubber_jonnie wrote: 03 Apr 2026 10:39

Cool, any screenshots? Any idea why the visual quality is poor?

I think that it’s noise on the colour clock.

No pictures at the moment. I’m not at home ‘til Tuesday now.

Fair enough, enjoy your Easter :)

rubber_jonnie wrote: 03 Apr 2026 12:46

stephen_usher wrote: 03 Apr 2026 11:57

I think that it’s noise on the colour clock.

No pictures at the moment. I’m not at home ‘til Tuesday now.

Fair enough, enjoy your Easter :)

This is the best output I can get. (It's supposed to be green on black.)


I think that I'm going to have to study the BBC Micro colour composite circuit and see if I can replicate it, by-passing the on-board circuit.

Oh yeah, that is a bit murky.

@stephen_usher my Lynx doesn't have composite out but the RF looks so much better than that. I use it with RGB-Scart and then through my OSC.

Btw, text will only be green on black if you enter the command "TEXT." Otherwise it's White on black and s...l...o...w...