Atari 7800 Repair

[yell0w_lantern]

I bought a broken 7800 on ebay. It was listed as not powering up and needing a good cleaning.

 

It arrived today.

 

When I flipped it over and saw 2 screws were missing, I had a feeling I was in for a ride.

The top RF shielding was gone and the power led had been snapped off of its leads confirming that someone had indeed opened the console before. The nasty surprise was a layer of something clear and sticky like someone had spilled soda pop in the thing.

 

Well, I soldered in a new LED, jury-rigged a power supply, soldered in an extra momentary switch in case the power button was busted, and replaced the capacitors. It actually powered up without the auxiliary switch. Unfortunately, the output consisted of noise and a black or grey screen with a rolling horizontal line and droning sound. Occasionally, the screen went white on power up and produced a crackling noise in the tv. Without a cart, I would occasionally get a blue screen or less frequently, a multi-colored screen.

 

I removed and reseated all the socket chips (none of which had any obvious physical damage).

 

I then cleaned the pins of the cart slot using de-oxit and a t-shirt over a credit card but without any improvement. I repeated cleaning the pins several times and I cleaned my test cart as well but still no improvement.

 

I intend to clean the pins one more time tomorrow after I remove the cartridge guide. However, I do not expect this to work.

 

So I am wondering:

1) What else should I try?

2) Is there anything that I can safely use to remove the sticky substance?

3) Should I continue to fail, does anyone here fix these things?

Edited May 17, 2014 by yell0w_lantern

[Osgeld]

1) What else should I try?

 

measure 5 volt lines to see if they are measuring 5 volts, if outside of 10% thats a problem

 

2) Is there anything that I can safely use to remove the sticky substance?

 

some high percentage isopropyl alcohol, the higher the better cause the rest of the mix is water, soak in a plastic tub and while submerged attack it with an old toothbrush, make sure its completely dry and then blow it out with compressed air, under chips and any components, let dry and repeat till no more liquid appears

 

3) Should I continue to fail, does anyone here fix these things?

 

try the above and report back, you could chip swap it, guessing till you get it, or you can find someone with more serious electronics tools (ahem) to diagnose it

Edited May 17, 2014 by Osgeld

[yell0w_lantern]

1) What else should I try?

 

measure 5 volt lines to see if they are measuring 5 volts, if outside of 10% thats a problem

 

 

Out of the power regulator?

[Osgeld]

yep

[yell0w_lantern]

4.95v so that looks okay.

 

Additional pin cleaning was no help.

 

cleaned off some of the gunk with 91% isopropyl and am waiting for it to dry.

[yell0w_lantern]

Needed a new 6502.