7800 acting up! Help please?

[RevEng]

Have you tried cleaning the cartridge slot? If one of the higher address lines has a dodgy connection, it would cause the console to always run in 2600 mode. Other address lines might interfere with 2600 bankswitching - it's a bit of a long shot, but cleaning it is an easy thing to do.

 

The tight fit with some carts is a 7800 hallmark, I'm afraid. Some people mod the console cartridge guide, cutting away part of it so it has more flex.

 

[edit - missed your reply to xucaen. Not a cart slot issue, then.]

[juggalot]

Yeah the resistor is connected to both ends of that broken trace. Thats why I figured it was intentional. I did think it was a little strange to make such a tiny hole to do it as well. I looked at the board quite a few times before I even noticed it. Do you think its possible that the little hole was an accident and maybe they just used the resistor to jump the connection instead of just using a wire? And maybe thats why this thing isnt working? Im far from an electrician so Im just throwing it up there. Also when you said 100-200 Ohm resistor, would that be 100k or just 100? Because I do have a 100k Ohm resistor I had bought for a controller mod but never used. And would I ground one end and the pins listed on the other end?

[juggalot]

I have tried cleaning the cartridge multiple times . I looked down inside with a bright light and magnifying glass and I didnt see anything. Although It is a pretty narrow slot. I used a credit card cut to fit and folded a thin cloth around the edge and spreyed it with contact cleaner. It didnt seem to leave any dirt or anything on the cloth either. Is there a better way to clean it that I could try? Or maybe My pins need bent back out a little? I did that to my NES awhile back.

[RevEng]

What you did to clean it should be fine.

 

If it's loose pins, putting gentle pressure on the front of the inserted cart should make the problem worse or better. That's one way to check, instead of bending them all and discovering it wasn't needed.

[juggalot]

ok thanks

[juggalot]

Well I woke up this morning and checked Craigslist like I always do and there was a 7800 for sale for $45 so I picked it up and it works great! It didnt come with a power adapter and only had one controller but I already had that stuff. It also came with four games. Donkey Kong 7800, Ms. Pac Man 7800, Air Sea Battle 2600, and Combat 2600. I opened it up and it has the exact same board as my malfunctioning 7800, resistor soldered to the leg of that one chip and everything. I feel alot better now.

[sn8k]

When I doubt buy another one. Or get in touch wth someone who can fix that stuff. Everything I have ever brought to my guy came back perfect.

[Stephen Moss]

Yeah the resistor is connected to both ends of that broken trace. Thats why I figured it was intentional. I did think it was a little strange to make such a tiny hole to do it as well. I looked at the board quite a few times before I even noticed it. Do you think its possible that the little hole was an accident and maybe they just used the resistor to jump the connection instead of just using a wire? And maybe thats why this thing isnt working? Im far from an electrician so Im just throwing it up there. Also when you said 100-200 Ohm resistor, would that be 100k or just 100? Because I do have a 100k Ohm resistor I had bought for a controller mod but never used. And would I ground one end and the pins listed on the other end?

 

I guess if you have 100's of boards to modify drilling a hole is quicker than cutting the track with a knife and removing the cut section. As you know having now purchased another one you know the use of a resistor was intentional, a break that small could easily have been jump with just solder or a small piece of wire such as a cut of resistor leg on the track side of the board so it would have made no sense to use a resistor if it was not necessary.

When I said 100 - 200 ohms I mean just that, 100K would not draw enough current out of the pin to create the necessary voltage drop, however as you have now purchased a second operation unit you should just keep the non functioning for spare parts.

[juggalot]

Yeah. I was thinking that. There's a Tedco Electronics down the street(I think it may be the last one left) that said they do repairs so maybe Ill drop it off and see what they can do. The guy that works there is about 90 years old and he's been there since they opened 50 years ago. I think he is the only reason that store is still open so I go to them for all my stuff. I fear when he dies the store will close up. Walking in there is like stepping into the past. The guy actually still writes up the receipts by hand and keeps the yellow copy. I know this is off topic but I think its pretty cool. First Ill get a resistor and try the reset thing you requested. Who know I may get it working eventually. Then Id probably just put it up for sale and give somebody else the pleasure of owning a 7800.

[+-^CrossBow^-]

Yeah. I was thinking that. There's a Tedco Electronics down the street(I think it may be the last one left) that said they do repairs so maybe Ill drop it off and see what they can do. The guy that works there is about 90 years old and he's been there since they opened 50 years ago. I think he is the only reason that store is still open so I go to them for all my stuff. I fear when he dies the store will close up. Walking in there is like stepping into the past. The guy actually still writes up the receipts by hand and keeps the yellow copy. I know this is off topic but I think its pretty cool. First Ill get a resistor and try the reset thing you requested. Who know I may get it working eventually. Then Id probably just put it up for sale and give somebody else the pleasure of owning a 7800.

 

I'd keep it as a parts board as well. Or..look at it and the working one over carefully to see if anything between them is really obvious to account for the issues? I know you stated they both have the bodge resistor in there, so I assume you removed the RF shielding from both? Do they use socketed chips or are they soldered in direct? Could try swapping out logic chips to see which is the culprit and then order the needed replacement from Best electronics...etc to get it up and going again.