A600 distorted picture

Hello, I have an A600 where the picture just isn't right. Connected to my monitor it looks like in the picture, but RF and component gives no signal at all. I figured it was the capacitors failing that did it so replaced them all, but still it looks just the same. Anyone have an idea what is causing this? Thanks

[Chucky]

JUST recap is not enough.. you also need to repair the damages the leakage did.

ofcourse, but here it was no damage, or leakage from any capacitors

[Chucky]

I wuld say: apparenlty there was......

[jimbob]

I think wonky references to the video encoder could cause this. Check carefully the circuits to pin 13 and 14 of U12. Double check your replacement C459 and C460.

From memory Vref on pin14 should be about 2V.

Check your cables are good too.

I get 2,9V on pin 14 of U12, the traces seems alright and there is continuity in all the right places ( I think ), double checked several of the capacitors and they are all soldered correctly. I removed the RF module aswell now, just to be certain that doesn't mess anything up. Still no difference to the signal.

Cables are alright aswell, as they work perfectly with my A1200

[supaduper]

Have you a Logic probe? Because then you can see if on U12 the RGB in signals are present at Pins 2,3,4 and the RGB out signals at pins 21,22,23, also its DENISE, U4 that generates the RGB signals so check around there too.

Thanks, I do not have a logic probe, I guess I should get one if I ever come over something like this again.

But I'm thinking that aslong as I have the right colors on screen that there should be RGB signals present, however there could be an issue with the sync signal, since it's so washed out?

[jimbob]

Not sure about that 2.9V, I had the number 2.1V in my mind but I'd have to check.

I'd be about 80% sure you have a faulty U12 at this point. Before replacing it though , you should check the transistor input & output to U12 as much as you can with a multimeter. Also check the filter/delay circuits around Z221 & Z222. Most likely fault here is SMD ceramic caps which can go open, short or resistive.

It's a bit tricky with a multimeter but you can do a lot of tests with resistance meter and conituity/diode tester modes.

I have traced and measured what I can do with a multimeter, also checked the composite port, and I'm starting to worry that you are correct jimbob, it looks like it has to be the U12 that's causing it somehow. Guess I'll just have to order a new CXA1145.

Might just get a cheapish scope aswell while I'm at it

After waiting for a few weeks on the new CXA1145, it finally arrived, replaced it, and at last it's working like it should again 😁