128K +2A Video output problem

[Haddocksknees]

Hello everyone, thanks for having me!

I recently bought a +2A, it works beautifully and is in pretty good nick apart from the video output, which is all dark grey and shadowy, this photo probably explains the problem better than I can



I'm using an RGB to SCART cable going from the RGB socket into a SCART to HDMI adapter, I know the adapter works as I've used it on a few of my other consoles.

I have replaced all the electrolytic caps, and also the TEA2000 as I thought this might be the culprit, I also tried swapping the RAM around as I read something somewhere about how either the upper or lower RAM banks can affect the video output ( But don't quote me on that, I'm still a bit of a noob to be honest )

And nothing changes, I can load games, the sound is working fine, but the screen is still grey and shadowy.. hmmmmmm....

Any ideas would be greatly appreciated, I don't want to have to replace every component if I don't have to.

Thankyou very very very much!

Steven

[Ast A. Moore]

This is typically what you get if the TV (converter box) doesn’t know it must switch to RGB and instead defaults to composite video. Since the +2A doesn’t have a composite video out and uses that pin for outputting a sync signal, this is the picture that you get.

You might want to consider a simple mod. For more information, take a look at this post as well as other messages in that thread.

[Haddocksknees]

Thankyou!! I'll have a look.

[Haddocksknees]

Hmmmm so I changed R44 to a 380 ohm resistor and I'm still having the same problem.

One thing I should've said is that there is no RF modulator on the board ( I think it was broken) so I can't test the RF signal, in any case this shouldn't matter if I'm going directly from the RGB port? Should it?

I don't want to have to buy a Raspberry Pi zero and a ZX HD just to get video output, maybe one day, but at the minute I just want to get it working!

This is the cable I'm using https://coolnovelties.co.uk/coolnovelti ... 06845.html

Could it possibly be the Scart to HDMI??

again, any help would be appreciated

[Ast A. Moore]

The cable looks like the correct one, although how correctly it’s wired is impossible to tell without taking it apart.

The RF modulator shouldn’t matter, nor should the TEA2000.

Check the logic board for cold/broken solder joints. Look at the DIN 8 socket and around the RF modulator. Make sure there are no broken or shorted traces there. Also make sure there is +12V present at R44 (the end opposite the DIN 8 socket). Measure the DC voltage across pins 1 and 2 and across pins 5 and 2 on the DIN 8 socket with nothing plugged into it and then with the cable plugged into the Spectrum and the SCART-HDMI adaptor.

Additionally, measure the DC voltage across Pin 16 and Pin 18 of the SCART connector while it’s plugged into the adaptor and everything is powered on. It should be somewhere between 1 and 3 V.