128 +2 Grey. The picture is not very clear.

[MrRomka]

Hello. Could you help me solve a problem with displaying an image through RGB? I have 0500 ISS3. I have already replaced all electrolytic capacitors, checked the power supply, flipped TR4, TR5, TR7, and TR8, installed a filter on TEA2000, disconnected LC2 and connected C31 to TR1.

The image is certainly much better, but still not perfect. Can someone advise me on where I need to go next?

https://lostpic.tk/images/2023/04/21/20 ... 132310.jpg
https://lostpic.tk/images/2023/04/21/20 ... 132303.jpg
https://lostpic.tk/images/2023/04/21/20 ... 132237.jpg

[drdivago]

Hmm, I don't think TR8 needs to be flipped, only the three 2N3904s.

[MrRomka]

Yes, you're right. I put TR8 back in place. I saw in one instruction a discussion about the correct installation of TR8, apart from the other three, and just decided to check. It doesn't affect the video in my case.

[1024MAK]

The relevant topic on WoSf is here.

TR8 is an PNP type (normally a ZTX213). It is part of the DC/DC converter and it’s important that it is fitted the correct way round, otherwise the +12V supply to the video system (and RS232/Aux port circuitry) will be out of tolerance.

Mark

[1024MAK]

@MrRomka what monitor/TV/display system are you using?

Mark

[MrRomka]

Mark, I use AIRIS MV149 17" monitor with an RCA video and audio input. Please find below a link to the instruction manual for reference, as well as an image and a short video file to better illustrate the issue.


https://drive.google.com/drive/folders/ ... 894QmJ7EaV

[cj7hawk]

Are you using RGB to display the image, or are you using Composite Video from the RGB connector?

[MrRomka]

I'm using Composite Video from the RGB connector.

I bought this cable:
https://coolnovelties.co.uk/coolnovelti ... cable.html

[Swainy]

If your TV has a scart connection then you need this one and you will notice a huge improvement:

https://coolnovelties.co.uk/coolnovelti ... results=23

[1024MAK]

If your TV has a scart connection then…

^ A RGB capable SCART (Euroconector) socket.

@MrRomka According to the TV instructions you posted a link to earlier, your TV does have a RGB capable SCART (Euroconector) socket.

For any one else who is reading this, on TVs or other devices that have more than one SCART socket, only one is normally RGB capable.

I can’t view your video on the device I’m currently using. I’ll power up my laptop later and have a look.

Mark

[MrRomka]

@1024MAK Hello. I've assembled an RGB according to this manual:

https://www.retrocomputershack.com/SCAR ... index.html

...but now when I turn it on, I briefly (for a fraction of a second) get a white screen, then a black one, and somewhere in the distance I can see the outline of the startup screen mixed with flickering blue shadows. There's anything I can check myself in this situation? Could the issue be with incorrectly installed jumpers in front of the RGB connector on the main board?

[spider]

This may be no help but when I had tried my +2 on two TV's via RGB scart, it worked fine on the larger Alba one but the "UNC" small TV (no documentation I can find either) it had a blueish picture then it would almost be like inverted video or outlines.

I concluded rightly or wrongly the voltage for each colour was too high or too low, but as it worked on the main TV i simply used that.

[1024MAK]

@MrRomka the normal problem with modern TVs with SCART sockets, is that they have automatic signal selection via the two control inputs on the SCART socket (pins 8 and 16). If these don’t have the correct voltages, the TV defaults to composite video. This will not work properly for a lead wired up for RGB video.

With some TVs these can be overridden via on screen menu options or remote control buttons. If the options exist, you want to select the RGB input for whichever AV input corresponds to the SCART input. Also if possible select 4:3 aspect ratio.

If there is no way to override the automatic switching via menus or remote buttons, then try the following:

• Remove the capacitor connecting between pins 16 and 18 on the SCART plug and remove the existing wiring to pin 16.
• Use a 12V regulated power supply and wire the positive to the SCART plug pin 8. This 12V on pin 8 selects TV on and 4:3 aspect ratio.
• Connect a resistor between SCART plug pin 8 and pin 16. The value is not critical as long as it’s between 330Ω and 560Ω. The aim is to drop the voltage to between 1V and 3V. The resistor acts as a divider when combined with the 75 resistor in the TV.
• Wire the 0V / common / negative to SCART plug pin 18.
• If you don’t have a suitable 12V regulated power supply, a new 9V alkaline battery (e.g. this size: PP3, MN1604, 6LR61, 6AM6, Rayovac A1604, Energier 522, Varta 4922) may work for testing purposes.

Mark

[MrRomka]

@1024MAK
Mark, good day. Thank you for your advice. I connected an external +12V, removed the capacitor, and added a 360 ohm resistor between 8 and 16, but I didn't see any difference. Perhaps the monitor is already in the correct mode, but there is simply no correct RGB signal? I have attached a picture below for clarity.



Thank you.

[Guesser]

That's ignoring the RGB signals so either your blanking voltage still isn't right, or that SCART socket lacks RGB input.

[MrRomka]

It is most likely due to the RGB signals. I found a switch in the TV for the scart mode: auto and manual. It was set to manual. I temporarily changed it to auto. Now the standby light on the TV changes from green to yellow when external power +12 is applied. This probably means that the switching is happening, but there is not working due to the absence of a signal. I will double-check everything. It's possible that one of the transistors before the RGB connector is faulty. Thank you.

[1024MAK]

The loss of one, or even two RGB channels should not result in the screen you have.

If there is a manual control for the SCART input, are there also any other controls or settings?

Another question, does this TV have two SCART sockets? If yes, normally only one will be RGB input compatible.

Mark

[oO cozy Oo]

I had a same problem with my +3 and found it was the power supply causing a poor grainy picture,have you changed or tried another ??

[MrRomka]

No, I didn’t change it, but I measured the voltage: 9V, with a load, as it should be. I'll try another power source. Thank you.

[MrRomka]

Hello everyone. I wanted to inform you that thanks to @1024MAK detailed explanation, for which I'm extremely grateful, I managed to connect the RGB board. There's just one small issue left to solve: there's a slight halo around the text and a black border. It looks like this:
https://img-host.ru/U0kti.jpg
https://img-host.ru/t4MY7.jpg

Sometimes, the image also vertically shifts, similar to what used to happen with old televisions. It might be worth looking into vertical synchronization.