MaxB Posted June 28, 2015 Share Posted June 28, 2015 Hello All, Just found this forum! I just bought a 7800 that was still in box, wrapped in its original plastic and everything. However, upon getting it home when I fire it up all I get is a white screen. Occasionally I will get some colored lines, but it wont display the games. Cables were all new in their plastic as well as power supply... This thing is a cherry! I tested the games again on my 2600 and they all work... Even the game that was with the 7800 (Pole Position II) wouldn't work. Pins still shiny gold!!! Any help would be great! Quote Link to comment Share on other sites More sharing options...
Shawn Posted June 28, 2015 Share Posted June 28, 2015 5v regulator would be the first thing I would check. Quote Link to comment Share on other sites More sharing options...
78001987 Posted June 28, 2015 Share Posted June 28, 2015 If I remember correctly, the original box for the 7800 was not shrink wrapped when it was originally released. It was the bare box with the sides glued shut. You might have been duped. Quote Link to comment Share on other sites More sharing options...
Shawn Posted June 28, 2015 Share Posted June 28, 2015 If I remember correctly, the original box for the 7800 was not shrink wrapped when it was originally released. It was the bare box with the sides glued shut. You might have been duped. Some came shrink wrapped with games. Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 29, 2015 Author Share Posted June 29, 2015 The box wasn't shrink wrapped, it was the console had its plastic around it. Also silver strip still had protective coating... Not a speck of dust inside of machine... How do I test the 5V regulator and where is that located exactly? Quote Link to comment Share on other sites More sharing options...
Shawn Posted June 29, 2015 Share Posted June 29, 2015 when you open up the console it's attached to the black heat sink behind the cartridge connector. Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 29, 2015 Author Share Posted June 29, 2015 Is this something that would typically fail just from age? I'm going to test it now. Thanks Quote Link to comment Share on other sites More sharing options...
78001987 Posted June 29, 2015 Share Posted June 29, 2015 when you open up the console it's attached to the black heat sink behind the cartridge connector.this. It's black, marked 7805c, has three prongs soldered to the 7800 motherboard, and has a screw through it connected to the metal heat sink. It's pretty easy to replace, even if you have mediocre soldering skills like me. 1 Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 30, 2015 Author Share Posted June 30, 2015 Just opened it up... There was a white paste all over the plate that screws the 5v Regulator to the back piece. I cleaned the paste off thinking it was like an oxidation from age. Plugged it back in, I got Pole Position main screen for about 15 seconds then white screen again... Any other thoughts? I am going to get a multimeter tomorrow so I can actually test the regulator... Quote Link to comment Share on other sites More sharing options...
RodLightning Posted June 30, 2015 Share Posted June 30, 2015 Regulator and power supply can definitely fail from age. It makes me wonder how often your 7800 was played. Heat and time are the usual culprits in that kind of failure. A multimeter will be your friend in checking for proper voltages at both the supply and regulator. Good luck and hope you are able to fix it. Keep us posted! Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 30, 2015 Author Share Posted June 30, 2015 Ok, so the 5V Regulator is working just fine... I tested both the in and out prongs... pulling in way over 10 and sending out right at 5.... According to what I read that is what it is suppose to be doing... So, I have a machine that powers on, has the right voltage but still has white screen when game is inserted... Like I said after cleaning that paste off I got the game screen for about 15 seconds... Looking for new ideas on what could be the issue. Dont want to trash this thing as it is so clean!!! Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 30, 2015 Author Share Posted June 30, 2015 I went back in to mess with it, fired it up and it came right on.... Thought I had it fixed by luck!!! Put case back on, replugged it in, and right back to white screen!!!! Ughhhhhh... WTF!!!!! Quote Link to comment Share on other sites More sharing options...
RodLightning Posted June 30, 2015 Share Posted June 30, 2015 This is the point where you might want to do some bench testing with the case open and a game cart in. The 5v regulator may still be a little flakey, or it could be a bad capacitor or cold solder joint somewhere. . Those should be eliminated before suspecting bad chips. You might try applying fingertip pressure here and there to see if you can temporarily correct a fault. Further troubleshooting will call for a soldering iron... Quote Link to comment Share on other sites More sharing options...
MaxB Posted June 30, 2015 Author Share Posted June 30, 2015 Will do! I'll play with it some more just to see if I can make a difference with pressure. Thanks for the info! I may just change the 5V just to see since it's literally a $1 part! Quote Link to comment Share on other sites More sharing options...
MaxB Posted July 1, 2015 Author Share Posted July 1, 2015 Found the problem!!!! Under the metal casing (I hadn't taken this off to expose entire board) there is one yellow wire that runs from one module to another. It has come lose on one side. I assume I have to put a drop of solder on that connection. When I hold it on there its perfect picture and sound! 3 Quote Link to comment Share on other sites More sharing options...
RodLightning Posted July 1, 2015 Share Posted July 1, 2015 Nice! I'm wondering if they all have a jumper wire like yours or if it was a factory correction in your particular model/series?Now I want to open up mine some time soon to see if it has the wire.Anyway, congratulations on finding the problem! Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 1, 2015 Share Posted July 1, 2015 (edited) Nice! I'm wondering if they all have a jumper wire like yours or if it was a factory correction in your particular model/series? They most certainly do not. This one is mine (with an AT-84 serial number and Expansion Interface). No jumper wires anywhere. Edited July 1, 2015 by DrVenkman Quote Link to comment Share on other sites More sharing options...
MaxB Posted July 1, 2015 Author Share Posted July 1, 2015 Well mine had one --- Re-soldered and fixed the issue... Perfect Pic & Sound Serial # on the bottom of this unit is 72R4BR A3 5251266 (There are two stamped numbers between the A3 & 5) These numbers are: 1 - Next to the 3 in A3 & 5 - In Front of the 5251266.... The wire according to your pic above went from the Maria Custom Graphics IC and the TIA Custom IC Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted July 1, 2015 Share Posted July 1, 2015 The board in your picture, is the rarest of the rare, all chips are socketed. I have 5 and none are like that. And yes, there are service center and factory units with jumper wires. They did all sorts of weird shit. EDIT: I was replying to Venkman. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 1, 2015 Share Posted July 1, 2015 The board in your picture, is the rarest of the rare, all chips are socketed. I have 5 and none are like that. And yes, there are service center and factory units with jumper wires. They did all sorts of weird shit. EDIT: I was replying to Venkman. Interesting. This is my only 7800. I expect the very early "EP" and perhaps also the "AT-85" units would be similar. As for jumper wires, yeah. I saw that when I disassembled my only XE machine a few weeks ago (a 130XE). Anyway, glad to hear MaxB got his machine up and running again! 1 Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted July 1, 2015 Share Posted July 1, 2015 Indeed, especially if it is minty. Quote Link to comment Share on other sites More sharing options...
RodLightning Posted July 1, 2015 Share Posted July 1, 2015 Well mine had one --- Re-soldered and fixed the issue... Perfect Pic & Sound Serial # on the bottom of this unit is 72R4BR A3 5251266 (There are two stamped numbers between the A3 & 5) These numbers are: 1 - Next to the 3 in A3 & 5 - In Front of the 5251266.... The wire according to your pic above went from the Maria Custom Graphics IC and the TIA Custom IC I cracked my 7800 open out of curiosity tonight and saw no jumper wire either. I've no clue what the wire in yours could be other than a trace repair done during production? All that matters is that another 7800 is back in play. Happy gaming. 1 Quote Link to comment Share on other sites More sharing options...
MaxB Posted July 1, 2015 Author Share Posted July 1, 2015 Here's a pic of my attic find. Exactly how I found it. Plastic still on, even the protective strip still on silver plate! Not a speck of dirt or dust on or in it! Absolute Cherry! How the cable came loose, I have no clue. Maybe that's why whoever owned it put it in the attic, because it never worked??? It's alive and kicking now!!! Thanks for all the feedback! 2 Quote Link to comment Share on other sites More sharing options...
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