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Old 22 November 2010, 20:25   #1
duga
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What's wrong with this A1200 motherboard?



Strange behaviour; the brighter the picture, the more scrambled graphics.
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Old 22 November 2010, 21:19   #2
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are you connecting the A1200 via composite video,RF or RGB?
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Old 22 November 2010, 21:21   #3
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are you connecting the A1200 via composite video,RF or RGB?
RGB.
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Old 22 November 2010, 22:08   #4
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maybe is your monitor or TV or the RGB out
also
test connecting the A1200 through composite video or RF to another TV
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Old 22 November 2010, 22:16   #5
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maybe is your monitor or TV or the RGB out
also
test connecting the A1200 through composite video or RF to another TV
It's not the TV as another A1200 and other devices like PS2 and STB:s works great through the same input.


I'll try composite and/or RF though!
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Old 22 November 2010, 22:36   #6
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Same problem with composite. Don't have a RF cable to test with.

The revision is 1D4.
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Old 22 November 2010, 22:48   #7
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Looks like a quick n' dirty job to me and I guess this causes the problem.
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Old 23 November 2010, 01:34   #8
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Same problem with composite. Don't have a RF cable to test with.

The revision is 1D4.
Ok ...then something is damaged on the motherboard
btw, that 3 cyan resistors do not exists on the original A1200 motherboard...it seems that someone put them ...who knows why
remove them and check what happens
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Old 23 November 2010, 07:47   #9
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Ok ...then something is damaged on the motherboard
btw, that 3 cyan resistors do not exists on the original A1200 motherboard...it seems that someone put them ...who knows why
remove them and check what happens
Remove the cyan resistors without replacing them?

The two brown resistors should be okay?
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Old 23 November 2010, 11:42   #10
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If memory serves the brighter a picture is, if the RGB component of the signal is greater than either 0.7V P-P or 1.0V P-P and someone will correct me here, then it causes this peculiar distortion and oversmearing.

You can never know why someone replaced various parts, it may have been done as a fix for *their* setup and of course with you having different devices then you can only expect problems.
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Old 23 November 2010, 12:04   #11
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@Fabie, It looks like those Cyan and brown resistors are "replacements" for the originals which are missing.

A1200 1D4

They don't look like extras. I suspect removing them and not replacing with suitable parts will end in tears.
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Old 23 November 2010, 19:39   #12
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Looks like a quick n' dirty job to me and I guess this causes the problem.
Hi

From what I can tell, the top two resisters that have been soldered in should not be there (the brown coloured ones). Looking at the top left, I think a capacitor should be there, and the top right should be just left blank. At least thats what I see on the web link given in an earlier post.
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Old 23 November 2010, 19:44   #13
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@AmigaFun: Nope, the blank one is still blank. All five resistors have replaced the regular one. I don't know why.

I bought this card placed in a tower in year 2000. It didn't matter then because I used a Mediator+Voodoo 3.
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Old 23 November 2010, 19:48   #14
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@AmigaFun: Nope, the blank one is still blank. All five resistors have replaced the regular one. I don't know why.

I bought this card placed in a tower in year 2000. It didn't matter then because I used a Mediator+Voodoo 3.
So E262C has nothing connected accross it? And E261C is still a capacitor?
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Old 23 November 2010, 19:52   #15
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So E262C has nothing connected accross it? And E261C is still a capacitor?
E262C = nothing.

E261C has a capacitor/resistor, I really don't know the difference.
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Old 23 November 2010, 20:21   #16
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Sorry duga, I cant really help much more. I have been looking at the circuit diagrams and just cant make out properly the component layout. Sufice to say though, if you have a resister where a capacitor should go you will run into problems.
Check also the underside of the motherboard for other modifications like you have on the top side.

Last edited by AmigaFun; 23 November 2010 at 20:32.
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Old 23 November 2010, 21:11   #17
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Maybe the brown resistor up to the right should be a capacitor instead? After all, it's called "E261C"...

Underside looks ok.
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Old 23 November 2010, 21:18   #18
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Maybe the brown resistor up to the right should be a capacitor instead? After all, it's called "E261C"...

Underside looks ok.
Yea, I would agree. If so, it should be 100pf, again looking at the circuit diagram.
As hinted though in a previous post, the question remains why this was carried out.
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Old 23 November 2010, 23:14   #19
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it seems that it is damaged the sony cxa1145 chip or the circuit after the chip
that's why the video is incorrect

to solve this problem you can connect a RGB cable to the connectors on the sony chip itself and should works fine
connect the rgb cable to pins 2,3,4 and 10

check the sony cxa1145 datashhet for more info

http://alexm.times.lv/CXA1145/CXA1145.pdf
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Old 24 November 2010, 21:13   #20
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At a closer look on the underside it seems that the RF module has been resoldered, maybe changed.

Maybe the best thing is to get rid of the card and forget it.
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