7800 video problems.

[Desh]

Hello! I am new to these forums. The first system I ever played was an Atari 2600 my dad had purchased in the late 70 ' s (I still have it). I am a classic gaming collector/ enthusiast and decided to pursue buying a 7800 to experience it's 8-bit wonder as well as play my old 2600 ganes on it.

 

I finally snagged one from a local game store with issues. It came with 2 controller's and the power supply. I knew going in there was a video issue (shop owner showed me before purchase) but, I have repaired/ modified many game consoles and for $15 I couldn't say no.

 

In the shop the console was hooked to an Atari RF switch box and displayed a blurry and skewed black and white picture but the sound works. I got it home thinking maybe something as simple as a dirty cart slot and went to town cleaning it. Still had the issue. So then I started thinking maybe an RF modulator issue and composite/ s-video modded the console since I wanted to anyways. The video is much more clear but still the same skewed black and white picture.

 

I have good power (13 volts in, 4.9 volts at regulator). I can't find any obvious visual defects on the mother board either. The only thing that was a bit strange to me is I am only receiving 4.6 volts at the power switch. Is this normal? I suspect I have a hardware issue somewhere but being new to this console I don't even know where to start looking and there isn't too much info available online. If anyone has any pointers I appreciate any advice.

 

NOTE* I currently only own 2600 games so those are all I have to test with.

 

[78001987]

Is it a pal console on an ntsc TV?

 

Pal 7800s have a fat rainbow sticker on the silver plating. NTSC has a thin rainbow, surrounded by raised milled metal outline.

[Desh]

It's NTSC... at least the shell is anyways. It sure does resemble a sync issue though.

Edited July 11, 2015 by Desh

[Desh]

Just an update. I figured out the problem. The problem ended up being my own stupidity.

 

I got in touch with one of my local collector buddies who is a big Atari freak. I ended up purchasing another confirmed working 7800 off of him. When I got the replacement 7800 home I installed my composite/ s-video mod and just copied my install from the previous machine. When I tested it I had the e act same issue. At this point I realized it had to have been something I did. I originally followed the install guide from electronicsentimentalities.com but the pictures are pretty poor. I looked at longhorn engineer's install guide and found I had remove the wrong resistors and hooked up to the wrong connection points (I counted one too many).

 

Anyways, now that I corrected the issue it works flawlessly. I also reassembled my original 7800 and it too works just fine. There are worse things in life than owning multiple 7800's.