reverendshoebox Posted November 11, 2013 Share Posted November 11, 2013 Hi, all. Got a problem with a recently-acquired Atari 7800 - when I plug it in and power it up, the LED comes on but there's no video or audio. Power supply is known working, TV and RCA cable / coaxial adapter are known working, cartridges tested are known working, and I've cleaned the heck out of the cartridge slot. I visually inspected the board for blown capacitors and don't see any. Not sure what to do from here. If it's just the RF modulator, I'm fine with that, because I'd love an excuse to try the composite video/audio mode. But how can I tell if that's the issue before I start down that road? Is there anything else I should check? Thanks much, -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
toiletunes Posted November 11, 2013 Share Posted November 11, 2013 Are you connecting to a newer (flat panel) television? The 7800 may not send a strong enough signal for this. Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 11, 2013 Author Share Posted November 11, 2013 Nope. And the TV I'm using works fine with another 7800 using the same cable, power supply, and coaxial adapter. Thanks, -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
YANDMAN Posted November 11, 2013 Share Posted November 11, 2013 I wanted a spare 7800 and believe it or not i purchased three.........yes three separate systems all in good boxed condition and they are all like this, I tested them on the same tv my current 7800 is tuned to but there is no picture and when i recycle on the tune it will never find a setting so it must be RF, Have you tried re-tuning, If it doesn't find it i would say you have the same issue, One seller wanted the console back the other two said throw them away i obviously wasn't going to do that but i think i now have two mod candidates, The only issue i have is being in the u.k i dont use s-video i want an RGB scart mod but im not sure one exists. Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 11, 2013 Author Share Posted November 11, 2013 Retuning the TV? Yes, I've tried that. No dice. Thinking it's likely to be the RF but I'd love to have some way of verifying that before I try the composite mod. Thanks, -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
ColecoGemini Posted November 11, 2013 Share Posted November 11, 2013 Only way to verify it is to plug it into a proper CRT tv. Some 7800s vary a bit in their output signal, and even though one will work with you LCD, another might not - but it may still work with a CRT. And if you do the "easier 7800 composite mod" you can find here, you can reverse it just as easily. Quote Link to comment Share on other sites More sharing options...
YANDMAN Posted November 11, 2013 Share Posted November 11, 2013 I only use crt's for mine, i tried my 7800 on my lcd and it looked horrible. Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 11, 2013 Author Share Posted November 11, 2013 I'm using a CRT. Sorry, thought I'd mentioned that but I see that I didn't. -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
+Mitch Posted November 12, 2013 Share Posted November 12, 2013 If you have a voltmeter check the voltage regulator inside the 7800 and see if it is outputting 5 volts. It may still output enough to power the LED but not the system. Mitch Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 12, 2013 Author Share Posted November 12, 2013 Yup, multimeter shows 5V on the voltage regulator...there does seem to be a bit of white powder around it on the heat sink... Anything else I could/should try? Thanks a lot, -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted November 12, 2013 Share Posted November 12, 2013 Try checking the 14-pin IC right below the power jack on the right-hand side of the board, that controls whether or not the system actually turns on. 1 Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 12, 2013 Author Share Posted November 12, 2013 Thanks for the response - what do I check there? -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
desiv Posted November 12, 2013 Share Posted November 12, 2013 Q: for those that know (which is NOT me).. Could he tap a few wires somewhere and hook them to an A/V input and see if he gets anything? I know the basic composite video MODs require an AMP (and some resistors, etc) for the video, but would he be able to see or hear ANYTHING just as a test with just some wires connected to some pins? That would at least tell him if the system/game is working?? desiv 1 Quote Link to comment Share on other sites More sharing options...
Rex Dart Posted November 12, 2013 Share Posted November 12, 2013 (edited) I imagine that if he tapped the audio points that the Easier Composite Mod taps, he should at least get audio. Probably would not get a picture without the amplifying transistor, though. Edited November 12, 2013 by Rex Dart 2 Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 13, 2013 Author Share Posted November 13, 2013 Thanks, I will give that a try. -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 14, 2013 Author Share Posted November 14, 2013 Alright...no dice on the audio. I hooked up the POKEY and the audio out as described and get no sound. Tried both an Atari 7800 cartridge and a 2600 cartridge. Nothing but a click when the power comes on. Apolloboy, what do I need to check on the aforementioned 14-pin IC? Anything else I should look at? Thanks, -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted November 14, 2013 Share Posted November 14, 2013 Apolloboy, what do I need to check on the aforementioned 14-pin IC?You could try checking pin 14 on it and see if you're getting 5V. Aside from that you'd need a logic probe to see if the chip is working properly. Quote Link to comment Share on other sites More sharing options...
YANDMAN Posted November 15, 2013 Share Posted November 15, 2013 This isnt related or anything that can help you but something very odd happened with my 7800 last night, Now nearly all my pal consoles tune in on the same channel and that channel has been set since about 89-90' when i got my NES, last night i was playing some NES then switched over to 7800 all on same tv same channel no issues, I then dug out my Super NES as i picked up a new game last night, plugged it in with same rf on same channel it came straight on no problems, I thought i would have a few games on pav-man collection before wrapping it up for the night but when i switched back over to my 7800 it had lost its tuning, re-tuned to the same channel and all was well again. Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 19, 2013 Author Share Posted November 19, 2013 Thanks - I checked, and yeah, I'm getting just under 5V. Am I basically stuck at this point without buying a logic probe? Any other ideas, guys? -=ShoEboX=- You could try checking pin 14 on it and see if you're getting 5V. Aside from that you'd need a logic probe to see if the chip is working properly. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted November 19, 2013 Share Posted November 19, 2013 Have you tried going through Atari's repair flow chart? http://atariage.com/forums/topic/216763-7800-theory-of-ops-ts-guide/? Mitch Quote Link to comment Share on other sites More sharing options...
Magic Knight Posted November 19, 2013 Share Posted November 19, 2013 Hi, all. Got a problem with a recently-acquired Atari 7800 - when I plug it in and power it up, the LED comes on but there's no video or audio. Power supply is known working, TV and RCA cable / coaxial adapter are known working, cartridges tested are known working, and I've cleaned the heck out of the cartridge slot. I visually inspected the board for blown capacitors and don't see any. Not sure what to do from here. If it's just the RF modulator, I'm fine with that, because I'd love an excuse to try the composite video/audio mode. But how can I tell if that's the issue before I start down that road? Is there anything else I should check? Thanks much, -=ShoEboX=- Just to check - is the power supply an original Atari or OEM equivalent? ive seen units power up to at least a LED on etc, but fail to play due to being on the power threshold. Im assuming the psu and cartriges have been tested on a friends machine before you know they are ok? Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 21, 2013 Author Share Posted November 21, 2013 Mitch - Thank you! I will check that out! Magic Knight - Yes, power supply and games are good, tested on another machine. -=ShoEboX=- Have you tried going through Atari's repair flow chart? http://atariage.com/forums/topic/216763-7800-theory-of-ops-ts-guide/? Mitch Quote Link to comment Share on other sites More sharing options...
ColecoGemini Posted November 23, 2013 Share Posted November 23, 2013 Considering the relative cost to find 7800 specific repair parts and pain in the ass to desolder if the problem is tia or Maria related vs. just buying another working console, it's probably easier to just keep this one for spare parts/repairs and just get another one the works. Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted November 27, 2013 Author Share Posted November 27, 2013 Yeah, I've already got a working one. Just was hoping I could get this one working as well. I wanna try the composite video/audio mod and I'd like to know I have a backup in case I screw something up. -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
reverendshoebox Posted December 20, 2013 Author Share Posted December 20, 2013 Giving up on this, annoyingly...so I guess I've got parts. Wheeeee, parts! On the plus side, I successfully did the composite mod on my working 7800, and it looks glorious. -=ShoEboX=- Quote Link to comment Share on other sites More sharing options...
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