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My 7800 won't power on


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#1 TerryMasters OFFLINE  

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Posted Fri May 28, 2010 8:14 PM

Hi everyone. I'm Terry Masters, and I'm hoping you guys can help me get my 7800 working again. For some reason it doesn't want to power up. I tried the original Atari power cable, and I just finished testing it with a 9v Genesis cable too but neither managed to get it to come on. When a 7800 doesn't turn on, and it's not the power cable, what could it be? I get the feeling someone shoved a third party cord in here at some point and damaged it, but I don't know where to look.

Thanks in advance guys,
-TM

#2 TerryMasters OFFLINE  

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Posted Fri May 28, 2010 10:55 PM

I took some pics of the board, incase it helps:

Posted Image
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#3 Mitch OFFLINE  

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Posted Sat May 29, 2010 12:31 AM

Could be the power button or voltage regulator. Do you have a volt meter or multi-meter?

Mitch

#4 TerryMasters OFFLINE  

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Posted Sat May 29, 2010 1:32 PM

Could be the power button or voltage regulator. Do you have a volt meter or multi-meter?

Mitch


Well I heard about the people having problems with the power button, but even swapping buttons didn't get it to come on. I do have a multimeter, where is the voltage regulator located?

Edited by Terry Masters, Sat May 29, 2010 1:34 PM.


#5 Mitch OFFLINE  

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Posted Sat May 29, 2010 5:16 PM

The voltage regulator is attached to the large heat-sink at the back of the board behind the cart slot. Put the ground probe of your multi-meter on the middle leg of the voltage regulator and report back on what the other two legs meter at.

Mitch

#6 thegoldenband OFFLINE  

thegoldenband

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Posted Thu Sep 1, 2011 4:05 PM

Bumping this thread because I have a similar problem. I bought my first 7800 recently, it came without a working power cord, I ordered one from Atariguide.com as recommended in the FAQ, and my 7800 won't turn on.

I've opened up the 7800 and tried following Mitch's instructions above. Assuming the voltage regulator is right at the top edge of the board, right below the nut used to attach the heatsink (?) and about 1/2" from being dead-center above the cart slot, then I'm getting nothing from it.

However, when I use my multimeter on the thingie (transistor?) marked MJE210, right between the power jack and heat sink, then I get a strong 11-12V reading. Furthermore, if I inadvertently bridge the center pin with either of the other two, the LED at the power light immediately comes on. I hope I'm not harming anything by doing that. :(

What steps should I take next? I don't have any soldering stuff, but I do have my multimeter at least. One other data point is that this 7800 originally came with a power cord from which the custom connector had been removed, leaving two bare wires. Maybe that offers some clue as to the previous owner's actions?

Edited by thegoldenband, Thu Sep 1, 2011 4:06 PM.


#7 thegoldenband OFFLINE  

thegoldenband

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Posted Thu Sep 1, 2011 4:18 PM

Whoa, update: when I bridge two pins on MJE210, the console boots! Karateka's there on my CRT, behaving normally as far as I can tell. What am I bypassing by doing this, and what does it mean for a fix?

EDIT: Even stranger, I managed to get the console to stay on without a bridge for a while. I'm not sure what I did, but I tried pressing all four of the buttons (power/pause/select/reset), all of which seemed to have the expected results except power, and ultimately it stayed on -- but I couldn't get it to turn off with the power button. Then when I cut power and tried again, it was back to requiring the bridge.

Edited by thegoldenband, Thu Sep 1, 2011 4:26 PM.


#8 Mitch OFFLINE  

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Posted Thu Sep 1, 2011 4:54 PM

Sounds like your power switch may be shot.

Mitch

#9 thegoldenband OFFLINE  

thegoldenband

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Posted Thu Sep 1, 2011 5:03 PM

Yep, that's it. I just tried applying some extra pressure to the switch, and the console powered on. I feel foolish for not trying that before! :dunce:

Other than desoldering the current switch and soldering in a new one, is there anything else I can do to temporarily improve it? Also, can I leave the upper RF shield off?

Edited by thegoldenband, Thu Sep 1, 2011 5:05 PM.





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