A1200 not displaying correct colours

Magno Boots · 07 September 2008, 17:48

Chaps,

One of my 1200's has developed a problem with the colour display. This isn't a gradual problem. It has happened overnight.

I'm not sure which colour is affected but black now appears green/brown and white also has a green tinge (see pics).

Attachment 17850

Attachment 17851

I have tried different RF cables and output via scart with no difference.

CFHD, idefix adaptor and accellerator have been disconnected - no change.

The machine has an internal CD fitted and I cannot see that the RF shield is pressing on something it shouldn't.

I'm loathe to remove the CD because it's glued in!

. I think I may have to. (more

)

Possibly a knackered chip?, all advice welcome.

Thankyou.

07 September 2008, 18:27

I know it sounds daft, but have you checked to see if its the tele is faulty and not the Amiga.

You want to try every combination of video sourced from the Amiga to alternate outputs.

IE:
the a520 adapter via RF to Lounge TV, Bedroom TV, Kitchen TV, etc
the a520 adapter via Composite to Lounge TV composite / phono scart, etc
a1200's composite video to Lounge TV composite, photo scart, etc
a1200's RGB 23 way D to RGB monitor, RGB Scart (TV)

and so forth. If they're all knackered then its gonna be a chip.

If you've got kids, question there move abouts around about the time the fault developed, look for the obvious signs of lying.

Sounds like an annoying problem.

Magno Boots · 07 September 2008, 22:20

Thanks for the advice Skipster.

I have tried different combinations of TVs and Amigas and the problem lies somewhere within the motherboard.

It has been completely stripped and a few dodgy looking solder points underneath have been 'touched up' so to speak. No joy.

The Alice chip is getting pretty warm, but I think this is normal.

I'm going to bin it and use the board from the miggy I found at the tip.

Thanks again.

rkauer · 08 September 2008, 01:39

Bad CXA1145 (video encoder) or busted/cold joint in one of the R-G-B SMD resistors right behind video encoder "entrance".

The CXA1145 can be replaced for a much more modern CXA1645 (fully pin-compatible).

coze · 08 September 2008, 02:00

please don't bin it, it sounds fixable, and I'm sure there are people on this board who would like a chance to give a new life to it. (read : me)

Hewitson · 09 September 2008, 05:49

Its likely to be the SMD resistors rkauer mentioned, I recently had a similar problem on a megadrive and they were the cause of it.

Measure them with a multimeter, you won't get an accurate reading because theyre in circuit but at least you can see if any are open circuit or reading ridiculously high.

twizzle · 09 September 2008, 13:40

@Magno Boots

dont bin it, mathew at amigakit can do MB repair`s

07 September 2008, 17:48	#1
Magno Boots Zone Friend Join Date: Feb 2006 Location: Hertfordshire Posts: 688	A1200 not displaying correct colours Chaps, One of my 1200's has developed a problem with the colour display. This isn't a gradual problem. It has happened overnight. I'm not sure which colour is affected but black now appears green/brown and white also has a green tinge (see pics). Attachment 17850 Attachment 17851 I have tried different RF cables and output via scart with no difference. CFHD, idefix adaptor and accellerator have been disconnected - no change. The machine has an internal CD fitted and I cannot see that the RF shield is pressing on something it shouldn't. I'm loathe to remove the CD because it's glued in! . I think I may have to. (more ) Possibly a knackered chip?, all advice welcome. Thankyou. Last edited by Magno Boots; 17 September 2008 at 23:04.

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07 September 2008, 18:27	#2
SkippyAR Posts: n/a	I know it sounds daft, but have you checked to see if its the tele is faulty and not the Amiga. You want to try every combination of video sourced from the Amiga to alternate outputs. IE: the a520 adapter via RF to Lounge TV, Bedroom TV, Kitchen TV, etc the a520 adapter via Composite to Lounge TV composite / phono scart, etc a1200's composite video to Lounge TV composite, photo scart, etc a1200's RGB 23 way D to RGB monitor, RGB Scart (TV) and so forth. If they're all knackered then its gonna be a chip. If you've got kids, question there move abouts around about the time the fault developed, look for the obvious signs of lying. Sounds like an annoying problem.

07 September 2008, 22:20	#3
Magno Boots Zone Friend Join Date: Feb 2006 Location: Hertfordshire Posts: 688	Thanks for the advice Skipster. I have tried different combinations of TVs and Amigas and the problem lies somewhere within the motherboard. It has been completely stripped and a few dodgy looking solder points underneath have been 'touched up' so to speak. No joy. The Alice chip is getting pretty warm, but I think this is normal. I'm going to bin it and use the board from the miggy I found at the tip. Thanks again.

08 September 2008, 01:39	#4
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	Bad CXA1145 (video encoder) or busted/cold joint in one of the R-G-B SMD resistors right behind video encoder "entrance". The CXA1145 can be replaced for a much more modern CXA1645 (fully pin-compatible).

08 September 2008, 02:00	#5
coze hastala vista winny vista Join Date: Feb 2006 Location: mt fuji Age: 46 Posts: 1,335	please don't bin it, it sounds fixable, and I'm sure there are people on this board who would like a chance to give a new life to it. (read : me)

09 September 2008, 05:49	#6
Hewitson Registered User Join Date: Feb 2007 Location: Melbourne, Australia Age: 41 Posts: 3,773	Its likely to be the SMD resistors rkauer mentioned, I recently had a similar problem on a megadrive and they were the cause of it. Measure them with a multimeter, you won't get an accurate reading because theyre in circuit but at least you can see if any are open circuit or reading ridiculously high.

09 September 2008, 13:40	#7
twizzle Registered User Join Date: Sep 2005 Location: taunton.som.uk Age: 73 Posts: 681	@Magno Boots dont bin it, mathew at amigakit can do MB repair`s

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