Amiga 2000 rev 6.2 - colours are off

Clad · 15 September 2018, 18:30

Hello,

The colours of my 2000 are off. Stock 2000, rev 6.2

I wrote a testscreen program to see the issue better.

Normal brightness:

https://drive.google.com/file/d/1bAk...ew?usp=sharing

You can notice the last 3 colours are a bit too red

Same output, Low brightness:

https://drive.google.com/file/d/1UP-...igVd4Oxj6/view

The red is actually fine

https://drive.google.com/file/d/139H...ew?usp=sharing

But there is an issue with the 2nd bit of the green (so XX0X and XX1X are always exactly the same colour, like $010 and $030 for instance)

https://drive.google.com/file/d/1gsC...ew?usp=sharing

Same issue with the 3rd bit of the blue (not exactly obvious on the picture, but when paiting the screen with like $8 and $C confirm it's exactly the same shade)

https://drive.google.com/file/d/11dC...ew?usp=sharing

I took the motherboard appart, I can't seem to see any fault (well, 3 fuses around the video output are gone & shorted, but the RGB signal fuses are still there)

The line drivers and the vidiot:

https://drive.google.com/file/d/1tNE...pL7vEwzN8/view

Denise herself:

https://drive.google.com/file/d/14-D...s7IEWnUgz/view

Any idea what could be wrong ? Ever happened to anyone ?

Thanks

Clad · 11 October 2018, 23:31

After messing a bit with the Amiga (opened/closed it a few time, trying an accelerator board, then putting it back exactly the way it was) one, I got the 3rd bit of blue back for some reason. Does that help a diagnostic ?

Also, I changed Denise, no difference. (it's not what got the blue back)

Franchute13 · 11 October 2018, 23:45

Hi.
Are you sure that the video cable and monitor work properly?

Clad · 12 October 2018, 10:11

Yeah, I have plenty so it was one of my first try. Beside, a fault in the cable would not give a display like this one: https://drive.google.com/file/d/11dC...XWdFbMd5t/view

It's clearly an issue with one of the colour bit, but it's not denise.

Daedalus · 12 October 2018, 13:31

Hmmm, there are a few things that deal with the colour in a bitwise fashion: there are logic buffer chips, pull-up resistors, and the video hybrid itself that could all be at fault. Also, check for debris or corrosion around the video slot - shorts here will cause bits to go missing on the analogue output. Given the temperamental nature of the fault, I would expect it's some cracked joints somewhere along the way, and the bending of the board from the troubleshooting has moved something enough to give good contact again.

15 September 2018, 18:30	#1
Clad Registered User Join Date: Sep 2018 Location: Toulon, France Posts: 19	Amiga 2000 rev 6.2 - 2 colour bits missing Hello, The colours of my 2000 are off. Stock 2000, rev 6.2 I wrote a testscreen program to see the issue better. Normal brightness: https://drive.google.com/file/d/1bAk...ew?usp=sharing You can notice the last 3 colours are a bit too red Same output, Low brightness: https://drive.google.com/file/d/1UP-...igVd4Oxj6/view The red is actually fine https://drive.google.com/file/d/139H...ew?usp=sharing But there is an issue with the 2nd bit of the green (so XX0X and XX1X are always exactly the same colour, like $010 and $030 for instance) https://drive.google.com/file/d/1gsC...ew?usp=sharing Same issue with the 3rd bit of the blue (not exactly obvious on the picture, but when paiting the screen with like $8 and $C confirm it's exactly the same shade) https://drive.google.com/file/d/11dC...ew?usp=sharing I took the motherboard appart, I can't seem to see any fault (well, 3 fuses around the video output are gone & shorted, but the RGB signal fuses are still there) The line drivers and the vidiot: https://drive.google.com/file/d/1tNE...pL7vEwzN8/view Denise herself: https://drive.google.com/file/d/14-D...s7IEWnUgz/view Any idea what could be wrong ? Ever happened to anyone ? Thanks Last edited by Clad; 17 September 2018 at 05:56.

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11 October 2018, 23:31	#2
Clad Registered User Join Date: Sep 2018 Location: Toulon, France Posts: 19	After messing a bit with the Amiga (opened/closed it a few time, trying an accelerator board, then putting it back exactly the way it was) one, I got the 3rd bit of blue back for some reason. Does that help a diagnostic ? Also, I changed Denise, no difference. (it's not what got the blue back)

11 October 2018, 23:45	#3
Franchute13 Registered User Join Date: Feb 2013 Location: Argentina Posts: 280	Hi. Are you sure that the video cable and monitor work properly?

12 October 2018, 10:11	#4
Clad Registered User Join Date: Sep 2018 Location: Toulon, France Posts: 19	Yeah, I have plenty so it was one of my first try. Beside, a fault in the cable would not give a display like this one: https://drive.google.com/file/d/11dC...XWdFbMd5t/view It's clearly an issue with one of the colour bit, but it's not denise.

12 October 2018, 13:31	#5
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,176	Hmmm, there are a few things that deal with the colour in a bitwise fashion: there are logic buffer chips, pull-up resistors, and the video hybrid itself that could all be at fault. Also, check for debris or corrosion around the video slot - shorts here will cause bits to go missing on the analogue output. Given the temperamental nature of the fault, I would expect it's some cracked joints somewhere along the way, and the bending of the board from the troubleshooting has moved something enough to give good contact again.

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