Atari 2600 jr repair question

[Duke]

My Jr has an issue with the color not being correct. I attempted to adjust it with the little adjustment wheel on the left side of the circuit board but it’s all out of whack. I’m pretty sure I need to replace it. It should be fairly easy (three solder points)  anyone know what that thing is a called and where I could get one?  Thanks so much. 

[Lohe]

Its an adjustable resistor, a potentiometer with 500kOhm. You can get it in any good sorted electronic business. Have a closer look to the three legs of the new one. They should be long enough to bend them into the solder points on the PCB. 

[Duke]

3 hours ago, Lohe said:

Its an adjustable resistor, a potentiometer with 500kOhm. You can get it in any good sorted electronic business. Have a closer look to the three legs of the new one. They should be long enough to bend them into the solder points on the PCB. 

I just ordered one. Thanks so much!  

[athousanddetails]

Duke, 

I had similar issues. If by any chance the pot doesn't fix it you need to change the following components as I had to do: 

Q5 - 2N3904

Q1 and Q2 - 2N3906 (check the component they might differ from revision to revision). 

C50 - 47pf Cap Ceramic / MLCC

C51 - 22pf Cap Ceramic / MLCC

C52 - 47pF Cap Ceramic / MLCC 

C55 - 22pF Cap Ceramic / MLCC

C48 - 820pf Polystyrene (Foil PS) or Polypropyelene Capacitor- Farnell / Mouser / RS have them.  Needs to be one of these. 

R36 - 4K7 resistor 1/4W 5%

R37 - 470 resistor 1/4W 5%

R56 - 1k8 resistor 1/4W 5%

R55 - 6k8 resistor 1/4W 5%

R9 - 500K Linear Trim Pot 

C22 - 1000pf/1nF/0.001uF Cap Ceramic / MLCC 

 

Also change all Electrolytic Capacitors... doesn't hurt and always help  big 2200uf 16V near power, and 4x 4.7uF 35V around the board. 

 

I had to change all this in order to get the colors back... for me changing the trim pot did not help at all. after doing this, i was back to life... than it's just a matter of trimming the pot and the RF Modulator at the same time to get the best possible picture (or do a Composite Mod, I would :P)

Let me know if the pot made it, or else go this route  q1, q5 and q2 and C48 are the biggest culprits for color display  

[ChildOfCv]

Ceramic caps do not fail that often.  I wouldn't even give them a second thought unless circuit testing directly pushes you into it.  Even more so for the resistors.  The styrofoam caps, though, could wear out.  And, of course, the transistors can die.

[athousanddetails]

9 hours ago, ChildOfCv said:

Ceramic caps do not fail that often.  I wouldn't even give them a second thought unless circuit testing directly pushes you into it.  Even more so for the resistors.  The styrofoam caps, though, could wear out.  And, of course, the transistors can die.

Well... In REV F they are tubular caps... which are known to be quite bad. a normal MLCC / Ceramic one does indeed last a ton. But in my case they were pretty much dead. And I also had R36 in very bad shape. I hadn't plugged my JR in roughly 15 or 20 years... + the age that it has. 

You can test for short or so... if they pass it doesn't mean they are OK. Same with readings... my C55 and C52 were 100% OK by the readings... changed them and voila much less interference more definition. Q5 and C48 were the ones to make colors appear on a wider range. 
So things are not that linear with this ? 

[Duke]

Thanks for all the advice. My part comes in this week. I’ll post a progress report. Thanks again!