exxos's Atari, Amiga & retro forum

I’ve got one, I’ll try it later. I have all sorts of colour behaviour depending on which display I plug it into, examples:

Late 80s Sony CRT: everything works fine
Mid 90s Panasonic CRT: colour doesn’t come in until ~1sec after the graphics appear (e.g when you change screens on Prince of Persia they are initially black and white for a second)
Mid 00s LCD: Black is very dark red, occasional flickers of correct colour

I’m fairly sure my colour killer switch doesn’t do anything and that text mode screens have no fringing. The adjustment wheels will alter the above behaviour somewhat.

At one point after I got it I got no colour on anything so bought a new TCA650 which brought it back - behaviour on the same display was inconsistent before that.

lilwashu wrote: 27 Mar 2023 10:18 I’ve got one, I’ll try it later. I have all sorts of colour behaviour depending on which display I plug it into, examples:

Late 80s Sony CRT: everything works fine
Mid 90s Panasonic CRT: colour doesn’t come in until ~1sec after the graphics appear (e.g when you change screens on Prince of Persia they are initially black and white for a second)
Mid 00s LCD: Black is very dark red, occasional flickers of correct colour

I’m fairly sure my colour killer switch doesn’t do anything and that text mode screens have no fringing. The adjustment wheels will alter the above behaviour somewhat.

At one point after I got it I got no colour on anything so bought a new TCA650 which brought it back - behaviour on the same display was inconsistent before that.

That would be fantastic, thank you. I am probably going to buy a new TCA 650, but I will measure the voltages with it removed first. They just don't seem right to me.

Interesting, when I check pin 4 with the TCA 650 removed, I get 5v. With it fitted it's half that, so I'm now wondering if the TCA 650 is marginal and pulling it down.

Pin 14 is 5v too, which doesn't make sense based on the schematic I have, however it does make some sense if you read that the pin 4 voltage when set to the supply voltage causes the IC to go into PAL mode.

It doesn't alter the fact that the datasheet states it should have a 12v supply.

Given the big drop on pin 4 from 5v to 2.5v ish, I am wondering if the TCA 650 is marginal, so I will order another.

I did also tweak the expansion socket for the memory card. It's working for now, but I'll continue to test.

lilwashu wrote: 27 Mar 2023 10:18 I’ve got one, I’ll try it later. I have all sorts of colour behaviour depending on which display I plug it into, examples:

Late 80s Sony CRT: everything works fine
Mid 90s Panasonic CRT: colour doesn’t come in until ~1sec after the graphics appear (e.g when you change screens on Prince of Persia they are initially black and white for a second)
Mid 00s LCD: Black is very dark red, occasional flickers of correct colour

I’m fairly sure my colour killer switch doesn’t do anything and that text mode screens have no fringing. The adjustment wheels will alter the above behaviour somewhat.

At one point after I got it I got no colour on anything so bought a new TCA650 which brought it back - behaviour on the same display was inconsistent before that.

If you don't have time, I've got a result from somebody on AppleFritter. They have 10.46v on pin 14 compared to my 5v. Their pin 4 voltage is a little higher, but broadly the same.

Oddly, I checked my 12v at the power connector and it was reading 7.2v. I powered it off and on and now it's back to 12.2v, and pin 14 now reads 10.17v, so I'm wondering if I have an issue with the 12v rail or if the PSU is unhappy.

On mine: Pin 4 = 2.5v, pin 14 = 10.8v. I'm not sure exactly what the colour killer switch is supposed to do on PAL systems, as the system remains in black and white mode until it sees colour.

Does anything happen if you adjust the colour trimmers?

lilwashu wrote: 27 Mar 2023 12:49 On mine: Pin 4 = 2.5v, pin 14 = 10.8v. I'm not sure exactly what the colour killer switch is supposed to do on PAL systems, as the system remains in black and white mode until it sees colour.

Does anything happen if you adjust the colour trimmers?

Thanks a lot.

Those voltages match what the person on AppleFritter gave me, but for some time I was getting just 5v on pin 14. I measured 12v at the PSU and was getting just 7.2v, but suddenly it jumped up to 12.2v and there was 10.2v ish on pin 14.

I am kind of thinking that I should recap the PSU as the overall weirdness I've been getting really does feel like bad power.

I've given the main power plug and socket a spray with Electrolube EML too, to see if that helps and I'm going to leave it running for a few hours, see what effect that has on the voltages from the PSU. I'm thinking that if it gets warm that could easily have an effect on bad caps if they are present in the PSU. No electrolytics on the mainboard, so happy days there, plus R31, CR5 and C95 all test fine and are what provides power to the TCA650.

I haven't adjusted the colour trimmers BTW as the colour is fine when it works.

As for the colour killer switch, it either allows 5v through to pin 4 via R72 when off (Giving the 2.5v reading) and allowing colour, or when switched on, it pulls pin 4 down to GND and when it is at 0v the machine outputs in mono.

I would recommend adjusting the trimmers (take a photo first), if mine are out of whack even slightly I get unreliable colour output.

lilwashu wrote: 27 Mar 2023 13:44 I would recommend adjusting the trimmers (take a photo first), if mine are out of whack even slightly I get unreliable colour output.

Mine are currently locked with glue and the colour is fine, it's just the screen has been flipping between mono and colour, sometime going blank when the voltage on pin 4 drops too low.

@rubber_jonnie sorry I didn’t see this sooner. Let me know if you still need anything.

PhilC wrote: 27 Mar 2023 14:25 @rubber_jonnie sorry I didn’t see this sooner. Let me know if you still need anything.

Cheers, I think I have what I need now.