Sears Video Arcade II Problem

[Mindfield]

Okay, so I got a Sears Video Arcade II cheap ($15), sold in known non-working condition by a seller who thinks it may be a loose contact or something. I've always wanted a SVAII or 2800 'cos they just looked s'damn cool, so I bought it on the strength that it may be repairable.

 

Today it arrived, so naturally the first thing I did was try it out with what it came with, and sure enough, no video. Or rather, I can sometimes see an extremely brief (like, a 1Hz flicker) shot of the game's screen before it goes black. In some cases (GI Joe: Cobra Strike for one) I get a single vertical line along the left side of the screen. Now, it came with an Atari-branded 10VAC, 750mA AC adapter, but I tried another one -- a newer known-working Atari-branded 9VAC/500mA. Same thing. I tried a universal 300mA adapter set to 9V/tip positive. Same thing again. No change with 12V or tip negative. If I power it up without a cart, I'll sometimes display a "garbage" screen (colour lines of random thickness in a thick swath) for a few moments before going black. (This lasts much longer than the brief flicker of a game being inserted)

 

Could this be something simple, like a loose connection? or is it perhaps the TIA? Or maybe the voltage regulator? Everything powers up fine -- the LEDs light up and the buttons function just fine, there's just no video display for more than a frame or so, if that -- just black. Any ideas would be helpful. I'd like to fix this baby up -- if I can do that I'll have a very sweet Sears-branded 2800 cheap. :-) Thanks!

[Mot]

Now, it came with an Atari-branded 10VAC, 750mA AC adapter, but I tried another one -- a newer known-working Atari-branded 9VAC/500mA. Same thing. I tried a universal 300mA adapter set to 9V/tip positive. Same thing again. No change with 12V or tip negative.

 

I could be wrong here but I thought putting 12V into something desighned to use 10V is a bad thing!

 

But I know you electronic geniuses will have more info.

[joesmooth]

No, that should be OK. I just picked up an SVA II last weekend at a flea market for $15 without a power supply. I'm using a 9VAC, 400mA supply just fine. Looking at the circuit board, the AC signal is rectified and then passed into a 7805 DC linear regular, and I don't think they are using AC for anything on the board (maybe the 60Hz for timing for something, but I have no clue). So, putting a 12VAC supply will probably not hard it.

 

I'd open up the machine (there's only a few screws) and reseat all the chips in their sockets (on my board, all the chips were socketed). Take a dust blower to it and look for any loose connections. The system is pretty integrated.

 

Good luck,

 

Joe

[Mindfield]

Socketed chips? Well that certainly makes things a lot easier. I'll have to check that out. Odydation is definitely a possibility.

[pmpddytim]

I'd open up the machine (there's only a few screws) and reseat all the chips in their sockets (on my board, all the chips were socketed). Take a dust blower to it and look for any loose connections. The system is pretty integrated.

 

I agree. I picked one up a a garage sale for $2 because the guy said is was toast. so I went home and tested it. It was acting like what the creater of this thread (sorry forgot the name) was talking about. Iopened it up and did almost exactly what joesmooth said and after that it has worked perfectly.

 

Tim

[CincYnoTi]

I'd open up the machine ...

 

I agree. I picked one up a a garage sale for $2 because the guy said is was toast. so I went home and tested it. It was acting like what the creater of this thread (sorry forgot the name) ...

Tim

 

when posting a reply, you can scroll down to the bottom of your window, and there is another scrollable window which displays all the previous posts. easy way to look for something forgotten.

[Mindfield]

Well, I just pulled the 2800 apart. Fortunately it's all socketed -- 5 small ICs around the main board and 3 larger chips under the RF sheilding around the cart port (I assume TIA, RIOT and whatever the other chip is). I pulled each of the chips, swabbed them down with isopropyl alcohol and re-seated them. I then shoved some cotton swab down into the cart port to clean the contacts (I can't figure out how to get the hood surrounding the port itself off of the board -- there are two clips on the underside of the board, but it seems to be held down by something else as well)

 

Unfortunately none of it appeared to help. There's a POT on the rear-left of the board (if you're facing the front), left of the cart port. I'm not sure what it's for but I suspect it's something to do with video synchronisation or colour correction. I don't wanna touch it 'til I'm sure though, and since I can't find and schematics on the 2800 I can't verify it.

 

That leaves me to suspect the TIA. Unfortunately I don't have a spare sixer to cannibalize. I have a spare Coleco Gemini I can gut if need be (the joystick ports are very fussy and probably need to be resoldered) but A) I dunno if they use the same parts, and B) I don't know (and sincerely doubt) if the chips are socketed. Coleco was all about cost cutting, so I doubt they'd have sprung for sockets.