Fried switchbox for Atari 5200 4-port system

[bargora]

Well, I've got a 4-port Atari 5200 system that I mistakenly left plugged in for a while, and when I powered it on last night, I got nothing but black screen. I changed over to my backup switchbox, and the picture was fine.

I've read that the switchboxes are easy to repair, and I've got basic soldering skills. I opened it up I saw that everything is nicely mounted with legs onto the board, so now I just gotta figure out which component fried and get a replacement. While the Atari 5200 faq (posted at Atari Age and gamefaqs.com) tells me how to build one from scratch, it doesn't seem to cover repairs to the original switch boxes. Any helpful hints?

[FABombjoy]

When you hit the power button, the screen turns black like there's no cartridge inserted? Or is it different than that? With the console off, does the normal TV picture come through? Do you hear the 'click' noise from inside the switchbox when you plug the power supply into it?

Reference http://www.atariage.com/5200/archive...witch_Low.html for schematics.

[bargora]

When you hit the power button, the screen turns black like there's no cartridge inserted?

Yes.

Or is it different than that?

No.

With the console off, does the normal TV picture come through?

Yes.

Do you hear the 'click' noise from inside the switchbox when you plug the power supply into it?

Yes. It may be my imagination, but it seems to me that the click sounds less "clicky" in the fried switchbox.

Reference http://www.atariage.com/5200/archive...witch_Low.html for schematics.

Thanks for the link. Unfortunately, I have only a general E&M course in my ejukation background, so that diagram is mostly just kicking my ass.

I posted this question at Atari Age as well, and was told by one person that there's a fuse that's probably blown. Another person said he was successful in repairing the switch box after replacing the small transistor next to the power plug and the OP Amp. Unfortunately, I don't know what the OP Amp looks like.

This thread at Atari Age has a photograph of the switch box PCB (with one blown component)--is the OP Amp the black 8-pin component in the middle of the left edge?
http://www.atariage.com/forums/viewtopic.php?t=16488

Thanks in advance for any further help!

[FABombjoy]

This thread at Atari Age has a photograph of the switch box PCB (with one blown component)--is the OP Amp the black 8-pin component in the middle of the left edge?
http://www.atariage.com/forums/viewtopic.php?t=16488

The 8-pin chip appears to be the LM393, which is a voltage comparator / op-amp. The fact that the switchbox still 'switches' suggests that it is probably operating just fine, although it could be providing insufficient output voltage/current to the 3906 transistor. I'm speculating here. My electronics skills are rustier than I'd like them to be.

I doubt it's a fuse problem, since the switchbox is the culprit and it doesn't contain any fuses. A fuse would have probably prevented the transistor in that AtariAge photo from grenading. Do you have a VOM? Since you have a working and a not working box, you could take some simple measurements on both boxes & see where the resistances/voltages are different. That is, assuming both switchboxes are the same hardware revision.

The 5200 power/switchbox setup is a really good example of over-engineering. I'm going to continue to hurt my brain with these schematics.

[bargora]

VOM = voltage/ohm meter, right? I've got a multimeter that at least does voltage and amperage. I'll see if it does ohms, too. Looks like I have a weekend project.

[Captain Wrong]

If nothing else works for you, the 5200 FAQ has a very easy to make replacement switch box for the 5200. That's what I'm using and it works great. Cost about $7 to assemble.

[bargora]

If nothing else works for you, the 5200 FAQ has a very easy to make replacement switch box for the 5200. That's what I'm using and it works great. Cost about $7 to assemble.

Yeah, I'm leaning toward the hombrew garage-hack switchbox solution. Thanks for the reminder, Cap'n.