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Repair questions 2600 jr rev e

repair capacitors troubleshooting 2600 jr poor video audio static

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#1 Xamfear OFFLINE  

Xamfear

    Combat Commando

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Posted Sat Apr 13, 2019 12:44 PM

Hello,  

So first a bit of a disclaimer - I am a bit of a noob when it comes to electronics repair et all - my soldering is crap, and I am definitely learning this stuff as I go along - so please pardon what I am certain is going to be apparent ignorance.

 

I have a 2600 jr rev E which is displaying poor colors (screen appears mostly greyscalish/monochromatic  with some yellow/green tinting on the sprites.  I tried adjusting the color pot, which  you can tell is affecting the underlying colors but onscreen the result is just changing the grey levels so the screen still remains mostly monochromatic.  Adjusted the RF pot to no effect either.

 

Low hanging fruit (IE assumption on my part) seemed like it might be a bad cap, so I purchased a recap kit from console5 for the JR.  Replaced the caps (polarity on the caps is correct)

 

Turned the machine back on, colors were perfect for 1 second, and then it reverted to the same symptoms, only this time with audio distortion as well.

 

Ordering ESR meter from amazon to check caps, but while I wait the two days for prime to deliver, I would love to get the communities input.

 

1) What should I be checking to troubleshoot this?

 

2) I have another 2600 jr  that works  (I haven't opened it yet so not sure what rev the board is)  - so I could desolder and swap TIA if that's appropriate  (my inclination is to socket the chips as well, my board has all three chips soldered to board - so if there is room, I think I will socket them)

 

3) This is probably a really dumb question - but I am curious all the same, the Jr cap kits comes with new caps for  C20, C26, C27, C29, C37

  • c26 is obviosuly the big cap @ 2200uF    16v
  • the other four c20, c27, c29, c37  are listed @ 4.7uF    35v in the console5 wiki (https://console5.com/wiki/Atari_2600)
  • That said the kit from console5 only comes with 3 replacement caps instead of four.
  • My particular revision lacks c29 so 3 caps were fine,  but  are there revisions which have all four caps on them? Or does each board revision have only a combination of three of those four caps?  

.

Thanks

Xamfear

 

 



#2 ChildOfCv OFFLINE  

ChildOfCv

    Moonsweeper

  • 391 posts

Posted Sun Apr 14, 2019 1:20 AM

Sounds like a power problem.  Check the voltage on A203's 3 pins, with the black probe on the shield.  You should have a pin reading close to 9V, another at 0V, and another close to 5V.

 

And to make sure your caps have correct polarity, arrowed stripe on the huge cap is pointing towards the controller ports?  The one near the coax out has the stripe on the coax out side?



#3 Xamfear OFFLINE  

Xamfear

    Combat Commando

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  • 4 posts

Posted Sun Apr 14, 2019 2:58 PM

Thanks for the reply!  Power is fine (went ahead and swapped out the regulator for the new one that comes in the cap kit.)

I double checked polarity on all the caps and they all are correct - big cap neg is toward the back,  one by RF out is correct as well.

Beginning to think the color pot is bad - even though I see some changes in picture when adjusting, I have seen several posts since I first posted this with people complaining about grey scale with yellow and it looks like it is the color pot that is usually the culprit.  I wrote Best electronics to see about ordering a replacement, so we will see when it comes in.



#4 ChildOfCv OFFLINE  

ChildOfCv

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Posted Sun Apr 14, 2019 9:56 PM

As you adjust the pot, what's the voltage range at C22 on the side facing the pot?



#5 Xamfear OFFLINE  

Xamfear

    Combat Commando

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  • 4 posts

Posted Tue Apr 16, 2019 9:21 PM

I'll measure this in the next day or so and get back to you.

Muchas!

-X



#6 Xamfear OFFLINE  

Xamfear

    Combat Commando

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  • 4 posts

Posted Fri Apr 19, 2019 10:31 PM

Replaced the color pot and get a great picture now with cvolor.  But still no Audio, just audio static, have replaced the two styrene caps at C53, C54.

 

Getting there.



#7 ChildOfCv OFFLINE  

ChildOfCv

    Moonsweeper

  • 391 posts

Posted Sat Apr 20, 2019 12:01 AM

First readjust the RF transformer (the red tower within the RF modulator) for best picture.  This could potentially bring the sound back too.  If not, go to the sound frequency adjust (the silver transformer below the RF modulator on the outside right of the RF modulator).

 

Handy picture for locating the adjust points:

http://www.the-liber...Motherboard.JPG







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