A1200 - Display too bright

[Rabbit80]

I just got an A1200 from fleabay and its got a slight issue... The screen is way too bright (to the point the background on the KS screen is almost bright pink)

Its a rev 1D4 board, I cant see any damage and the caps look fine. I'm on Composite output at the moment - but apparently it is the same through the rf output!

Any ideas?

Pr0n on Page 2

[TheCorfiot]

@rabbit80

Would be interesting to know if the RGB output from the 23way Video port is normal.
If it is normal, this may suggest a fault with the CXA video encoder on the Motherboard, if you don't have a scart lead try running an A520 from the video port instead.

TC

[alexh]

RGB SCART cable will probably fix it. It depends where the component failure is.

[Rabbit80]

I guess I'll order one... Any suggestions on the cheapest place to buy a ready made one?

[Angus]

Originally Posted by Rabbit80

Any ideas?

(I'll try to post some pr0n tomorrow)

I rememeber shortly after the 1200 was released there was a bunch that had problems with the TV signal. I think Wang(?) had to fix them. I wonder if the owner has always used a monitor and so didn't have the problem.

[Rabbit80]

Originally Posted by Angus

I rememeber shortly after the 1200 was released there was a bunch that had problems with the TV signal. I think Wang(?) had to fix them. I wonder if the owner has always used a monitor and so didn't have the problem.

Any more info? I have an A600 that I can rob parts from - Anything that I can swap?

[TheCorfiot]

Before you start robbing & changing parts have you determined the cause of the problem.

It would probably still be less mess to use an ext A520 even if the encoder on your mobo proves to be at fault.

Of course going for an RGB Scart cable will give you the best display & is the option I would recomend.

TC

[Rabbit80]

Any way to output to component video? or HDMI...?

[alexh]

You could by a converter but why bother? Most new LCD/Plasma TV's have RGB SCART and RGB VGA input.

You can use a 23-pin to 15-pin VGA dongle to connect to a Plasma/LCD via VGA input. You will have to use DBLPAL or DBLNTSC. Wont work in most games but works for workbench.

Or you could get an Indivision scandoubler... but save £100 and just use the SCART socket with RGB cable!

[Rabbit80]

Originally Posted by alexh

You could by a converter but why bother? Most new LCD/Plasma TV's have RGB SCART and RGB VGA input.

You can use a 23-pin to 15-pin VGA dongle to connect to a Plasma/LCD via VGA input. You will have to use DBLPAL or DBLNTSC. Wont work in most games but works for workbench.

Or you could get an Indivision scandoubler... but save £100 and just use the SCART socket with RGB cable!

Except I have my PC on VGA input (And on HDMI but it has a few issues with high resolution from PC through this), A PVR and a DVD on Scart leaving me with just Component, HDMI or Composite / sVideo... I guess i could get a scart autochanger though...

[alexh]

Your PVR and DVD should be capable of component out and S-Video out.

Both are natively encoded in the S-Video colour space and so using S-Video should not affect quality that much.

[Rabbit80]

I've completely failed in my quest to build a RGB-Scart cable... I've double checked my work and my TV just will not accept it So - I cannot play my A1200 until such time I can afford to buy a cable!!!

[DDNI]

Rabbit, remember to bear in mind that not all TV SCART inputs support SCART RGB.

[TheCorfiot]

Rabbit

Post your wiring connection list so we can have a look at it for you.

TC

[alexh]

You have the wrong voltage on the FAST BLANK pin

[Rabbit80]

Originally Posted by alexh

You have the wrong voltage on the FAST BLANK pin

Yeah - I also think this is the problem... I have pin 22 Amiga to 16 Scart via a 150 Ohm resistor... I have also tried from pin 23 through same resistor.

Is there anywhere a definitive guide to the correct pinout so I can check again - I kind of cobbled together a few sources but then I got annoyed when it didnt work!

I have:

Amiga -- Scart
3 -- 15
4 -- 11
5 -- 7
10 -- 20
16 -- 13
17 -- 9
18 -- 5
19 -- 17
22 - 1K - 8
22 - 150 OHM - 16


I did have pin 19 Amiga on pin 20 - Cant remember why I changed it. I also tried pin 23 Amiga to 16 Scart via the same 150 ohm resistor.

[Rabbit80]

Originally Posted by DDNI

Rabbit, remember to bear in mind that not all TV SCART inputs support SCART RGB.

Mine does

[DDNI]

Originally Posted by Rabbit80

Mine does

Happy days then! Good luck with it

[alexh]

Originally Posted by Rabbit80

Yeah - I also think this is the problem... I have pin 22 Amiga to 16 Scart via a 150 Ohm resistor... I have also tried from pin 23 through same resistor.

Use a multi-meter if you have one to check the voltages on the Amiga pins.

Originally Posted by Rabbit80

Is there anywhere a definitive guide to the correct pinout

Unfortuntely not.

Originally Posted by Rabbit80

I have:
Amiga -- Scart
3 -- 15 (RED)
4 -- 11 (GREEN)
5 -- 7 (BLUE)
10 -- 20 (Composite Sync)
22 - 1K - 8 (AV select / Aspect Ratio)
22 - 150 OHM - 16 (RGB select)

All looking good. Although you need to check the voltages on PIN8 and PIN16 as you may need to change the resistor values to suit your Amiga.

Amiga Pin 22 = 12v
SCART Pin 8 = 9.5-12V (Auto Switch to AV channel in 4:3)
SCART Pin 16 = 1-3V (Use RGB rather than composite)

Originally Posted by Rabbit80

Amiga -- Scart
16 -- 13 (RED GND)
17 -- 9 (GREEN GND)
18 -- 5 (BLUE GND)

These all look good. I am not 100% sure which grounds you have to wire up.

I personally start making an Amiga SCART cable by wiring up all the grounds together in back of the SCART Plug using very short loops of wire and solder. Then when I connect them to a single ground on the Amiga side everything should work great.

Originally Posted by Rabbit80

Amiga -- Scart
19 -- 17 (CV GND)

This should be 19 -- 18 shouldn't it? I doubt it matters.

Originally Posted by Rabbit80

Amiga -- Scart
I did have pin 19 Amiga on pin 20 - Cant remember why I changed it.

Because it would be wrong? Pin 19 on Amiga is composite sync/video ground and pin 20 on SCART is composite video in which is already wired to pin 10!

You seem to be missing SCART pins 21 (the shield) and 14 which can be wired to a ground. Most TV's work without any grounds but perhaps yours is particularly sensitive. Without them the TV might not be able to measure the voltages on pins 16 & 8 and correctly.

When you switch on your Amiga does your TV automatically switch to the AV channel?

[Rabbit80]

Originally Posted by alexh

What you seem to be missing is you MUST wire up SCART pin 21 (the shield) to a ground or the TV might not be able to measure the voltages correctly.

I forgot to mention that... It was already in place....