Debug Help - No sound (only static) on a 4-switch Vader 2600 unit

[Trellot]

Hi all,

 

I've recently purchased a 4-swtich 2600 Vader unit but I only get static noise, no sound at all from the unit. Great video though! Looking for some suggestions on how to resolve this issue if possible.

 

What I've done:

 

• Cleaned mainboard top and bottom with alcohol and toothbrush
• Dismantled and cleaned all the switchs which now work great
• Electrically tested voltage regulator and power jack (all well within range)
• Noticed rust under the RF shield and the top and bottom plates had some rust on them which I've abraided away.
• Tried the sound adjusting coil but got nothing from that
• Tuned the RF Modulator without success
• Noticed a rusty base on the RF modulator box so I desoldered it and cleaned it all up (rust on the board underneath which I've also cleaned well)
• Resoldered the RF modulator but get the same static noise
• Replaced the sound adjust coil with another working unit (no dice).

Should there be anywhere else that I need to look other than the RF modulator? I've read that the TIA also manages sound as well?

 

Any suggestions would be appreciated! As it stands now all is perfect except the static noise I get.

 

Thanks,

 

Trellot

[SignGuy81]

That is correct about the TIA but it is probably in the circuitry between the TIA and the RF.

[SignGuy81]

http://www.robotsandcomputers.com/computers/manuals/atari2600_fsm.pdf

 

page 42 of 156 of the pdf

 

i would at the two 820pF(C206, C207) caps and the NPN transistor(Q201), and with system on make sure you have your +5VB in the circuit shown also you can follow troubleshooting steps on page 121 of the pdf I linked above.

[Trellot]

Thanks Signguy81,

 

I tried shorting L202 on the mainboard and immediately I got clear sound from the unit. After the short, all the static went away and I was getting good sound; not without anomoly however with some repeating of sounds and some game play weirdness. Should this L202 module be replaced or could it be another component inline? I'm a noob to all of this so nothing necessarily stands out and glares me in the face lol! I will also try your suggestion above and report on that.

 

Trellot

[SignGuy81]

Sounds like L202 may be open or bad solder joint(s) at it that may need to be reflowed.

[Trellot]

I will definitely reflow those joints and should the static return I'll replace that L202 part. Thanks for your suggestions!

 

~ Trellot

[Trellot]

UPDATE:

So just this last weekend I finally got this system working. I was in the market for the 1.8mH inductor but was warned away from thinking that was the issue from Best Electronics. They mentioned I should try replaicing the the two polystyrene sound capacitors on the board which I ordered and replaced. Didn't solve the problem. The problem morphed from having only static and not being able to play the games to having good video and sound after performing that short. But then on games like PacMan Ms. Pacman and Jungle Hunt, etc., the game would perform a sound glitch and freeze or in Jungle Hunt's case would start the game at the aligators but you couldn't play. So, I then decided to try swapping out chips but they were all soldered down on the main board, sigh! I chose to pull all the chips and socket them for ease of use in the future and it paid off since it ended up being the last chip I socketed, the RIOT chip. Now the system plays great, although I get a little buzzing noise every once in while during gameplay. Not sure why that's happening? I tried adjusting the sound coil and the rf modulator and it makes a little difference but the buzzing just sort of slips in now and then. Overall, I'm happy the results! I'll post a pic soon of the finished product!

~ Trellot

[Trellot]

FINAL UPDATE:

I realized I never finalized this post with the latest details.  What I ended up doing with this unit was to perform an AV Mod upgrade on it and and pulling out that RF Modulator.  Now the unit looks great, plays great and sounds great!  I recently gifted it to my brother who is having a blast with it.   Well, that's it!  Have a great day everyone!

 

~ Trellot