Repair tips for a 2600

[rigues]

Hi Folks,

 

I'm facing a weird problem while trying to repair my girfriend's 2600, and thought someone here would be able to shed some light on the issue. It's a 4-switch Polyvox machine (from Brazil), made circa 1986. The problem is: some colours on the image are missing. You can see a good representation of the issue here:

 

http://www.caetano.eng.br/rigues/temp/DSC04430.JPG

 

As you can see, green is missing. At first I thought the problem was on the internal transcoding board (NTSC->PAL-M) and removed it, bringing the console back to NTSC (most modern TVs in Brazil show NTSC anyway). Seeing that it had no effect, I turned my attention to the RF module, and did an A/V mod [1] on the machine. Still no deal, so I tried the TIA. The chips are all socketed, and at first I replaced the old worn-out TIA socket with a new one. As a last resort, I spent 4 hours scouring the electronic component shops here in São Paulo looking for a new TIA. I lucked out and found a shop with few pieces of a compatible part (KSC131) in stock and bought two, but even those didn't solve the problem.

 

Does anyone have any idea on what might be going wrong? Any parts that I should check? This console means a LOT to her, and I really want to get it back on a working condition.

 

[1] - The A/V Mod (portuguese): http://sti.br.inter.net/elucas/artigos/Atari-AV/

 

Thanks for your attention!

Edited June 9, 2007 by rigues

[opeygon]

You may try contacting an atari age member by the name of A.J. Franzman. He has helped answer a couple of questions of mine and seems very knowledgeable about all the atari tech thingies that I know nothing about. If you are reluctant to contact him, just hang around and watch your post, he may answer, or try posting in the hardware thread here at atari age.

 

Good Luck

 

Edit:

 

A.J. - hope you don't mind that I dropped your name here

 

Opeygon

Edited June 9, 2007 by opeygon

[A.J. Franzman]

I don't mind the name dropping. I usually read all the posts with topics about 2600 hardware issues, and comment on many of them (some folks might consider me a post whore that way), but I didn't post in this one because I thought I had nothing helpful to say.

 

Losing some colors but not others suggests a TIA problem, but rigues said he replaced it with no improvement. The easiest way to make sense of that would be if someone made a bunch of defective TIAs, and he replaced one bad one with more bad ones from the same lot. Other very remote possibilities are low system voltage (but I would not expect two TIAs to behave identically in that case, much less three), or an RF modulator problem (could be some kind of bizarre failure, or simple slight mis-tuning), but riques says he's using an A/V mod now, so that possibility is eliminated too.

 

@ riques: are the TIA that was in the console and the replacements you bought marked the same way?

Edited June 12, 2007 by A.J. Franzman