Space Invaders power supply

[P-feif]

Well the game quit working, and I couldn't get the voltages to work so I installed a cap kit in the power supply. Still couldn't get the voltages right and game still didn't work. So I installed a cap kit in the mother board, touched up dozens of cold solder joints and then... I did something non of us should EVER do. I used solder to touch up the board edge where the wire harness connects to it. I know I shouldn't have done it, and normally I wouldn't BUT I noticed that someone in the past had already done it so I figured the harm had already been done and I can always install a edge replacement and new harness connector sometime in the future as I did in my Ms Pacman. And wa-la! The game came alive, BUT the voltages are still not right. I figure that something somewhere has high resistance and so the amps are probably high (no I didn't measure the amps, I don't know what the amp spec is so until I find that info why bother?) and high amps usually lets the smoke out at some point. So that's what I'm trying to avoid. At this point the game turns on a works as it should, just with funky voltages. Heck I've set the pots right in the center with the voltages at 4.6 and -5.4 and it still works. So chase down the problem or live with it? I don't know, let it run for awhile and see if I can find something hot to the touch on the mother/daughter board set? I'm really not sure how to go about this at the moment. If I just let it cook itself that would be one way to find the problem. Probably not the best way but I'd find it. 

[iankellogg]

Just leave the power supply alone. You are chasing nothing at this point. As long as its near 5V you are fine.

[P-feif]

O.k. I'll try setting it at like 4.85 volt so that I don't have the pot pegged and I'll move on. Maybe I'll rebuild the control panel.

[iankellogg]

Nothing wrong with the pot pegged, get as close to 5V and leave it.

[P-feif]

O.k. Thanks Ian.

[P-feif]

I haven't had time to work on this in a while. A buddy stopped by this last weekend and I plugged it in to let him play a game. The bom BOM bom BOM sound of the alien ships marching across the screen was gone. It's never given me trouble before. Also since I haven't worked on this in a while the above stated voltage problem has not been fixed. So I'm wondering. If I was having a problem with not being able to achieve +5 or -5 volts with the PCB plugged in, to me it seams that something on the PCB is loading down the power supply. Now all of a sudden one of the sounds is missing.... Is it possible that whatever was loading the power supply finally died? Keep in mind I haven't had time to plug it in and check if my voltages are still messed up or not. But let's just assume that's what happened, my guess is a chip for that sound is bad, so which one is it? Yes I know I really need to check my voltages before asking that question.

[P-feif]

O.k. been since last spring. Weather is getting cold so back to indoor project. Time to get this Space Invaders done so I can move on to another game.....

Bob Roberts is still closed, I need to replace the PCB board edge and repair the pins in the connector or replace the connector any idea's where I can get this stuff. (Ian I'll buy them from you if you carry this stuff.)

By the way I'm doing this because I'm still having a voltage issue. Still can't get 5 volts or -5 volts with the PCB plugged in. I noticed that the edge of the board is in bad shape. I don't know for sure that this is the problem but if the board edge is in bad shape and I can fix it then it's one more thing that I can rule out, and it needs to get done anyhow. Same for the connector, someone in the past soldered the board edge so I'm pretty sure the pins are spread, I may be able to gently bend them back up if I can replace the pins/connector then I'll do it.

[P-feif]

So, I haven't had time (as usual) to work on this, BUT... I did contact the guy that I bough the Space Invaders from and he had a spare PCB and spare power supply, both of which he had sent out and repaired. He said he hasn't tested them yet, however he loaned them to me so I can try them in my game. This should hopefully let figure out if "MY" PCB is pulling down the power supply, or if "MY" power supply has an undiagnosed problem even after I recapped it. First thing I'm going to try is to use "HIS" PCB with my power supply. Then "HIS" power supply with "MY" PCB. I'll let you guys know what happens, when I get to it.

[P-feif]

O.k. So I tried my friends power supply and it was bad, wouldn't make any volts at all. So I put my power supply back in and tried it with my PCB and got the same results that I've been getting. +4.7 volts and -5.2 volts. Can't make 5 or -5. So then I put in my friends PCB and got the exact same result. So this points to a power supply issue and not a PCB issue.

Also I noticed today that when I was using my PCB the background sound (bum Bum BUM Bum, bum, Bum, BUM, Bum) is gone and when the mother ship flies by the sound is very weak and tiny. All other sounds working fine. This bugs me. It WAS working. I'm sure my power supply issues didn't do it any good.

So anyhow one of the caps that I got from B. R. was a different capacitance and I questioned that but was told that the power supply would work fine. Now I'm questioning it. It was one of the two big filter caps. I know that B. R. was trying to sell me a cap that saved me some money but I'm wondering if I should just spend the money and buy the expensive caps and give it a try. Only other things that I can do is remove one component at a time and test them, or just get a switching power supply and adapt the game to use it. Personally I like having the original stuff, but I guess it is inside the game where you can't see it.

So what do you guys think???

Edit: just thinking about this. The reason I replaced the capacitors to begin with was this voltage problem so I doubt it's the new capacitors. Hmmmm.

[P-feif]

I am suspecting that the 2n3055 transistor on the large heat sink might be bad. Looking at the print it is the only part that is part of both the -5 volt and +5 volt circuits. On Mouser I found a 863-2n3055g. Anyone know if it is compatible? Ian?

[P-feif]

Wow I can't believe I haven't worked on this thing in that long. Any rate I finally found time to putts with it..............

MONTHS ago I bought the transistors that I listed above, along with some others and decided to check them, however before I put them in I had watched a youtube video where someone having the same issue as me found the big ceramic resistor (.18 ohm 5 watt) was bad he changed it and his problem was fixed. I looked at the print and saw that it "could" be an issue so I pulled it out of circuit and low and behold it was WAAAAY out of spec. So I ordered a new one and changed it. DID NOT FIX ANYTHING. So this morning I changed all the transistors that I had purchased for it. Did not have time to turn it on and see what it does and I didn't have time to use my meter to test the transistors either so I'm not sure that it's fixed. If it's not, after looking at the print there are a bunch of resistors that are sort of in the middle of the +5 and -5 volt circuits and could effect them both so I'll start pulling them out of circuit and testing them, along with some of the diodes (there are too really big diodes that the board under them looks burned, Hmmmmm?). There isn't a lot more to look at here. I'm even starting to wonder if the transformer is making enough voltage for the power supply to work so I'm probably going to check that too. I honestly can't believe that I don't have it fixed yet.

[P-feif]

Decided to give up on the original power supply. I bought a brand new switching power supply with the 8080 adapter from The Arcade Shop. Just installed it set 5 volts with the processor disconnected, turned the game off, plugged in the processor and turned the game on. The new power supply turns on for a few seconds and then goes into shut down. I shut the game off confirmed my connections and turned it on again. Same problem power supply comes on for a few seconds and then goes into shutdown. Something on the processor board has got to have a short.

Any ideas would be appreciated.......

[P-feif]

So I needed to change the wire harness connector for the pcb because I knew it was not in the greatest shape. Was really hoping that it would solve the problem. Nope. Brand new power supply goes into shut down  with the pcb hooked up. I’m at a total loss. I would really appreciate if some of you gurus would reply. I’m going to call arcade shop sometime this week but I’m really lost on this problem and could use some friendly advice.

[P-feif]

Talked with Arcade Shop today. I felt that this thing must have a short on the PCB. There is one sound missing (thump thump sound) and the flying saucer sound is really weak. The guy I talked to at Arcade Shop felt that one or both of those chip is most likely shorted to ground and at the very least I should investigate that. I was sort of getting that feeling too, but really wasn't sure until I talked to this guy. So hopefully sometime soon, I'm going to pull those two chips and see how the board runs without them. It won't have those sounds but it should (hopefully) at least run. I'll let you know what happens after I get a chance to work on it.

[P-feif]

So I pulled the two chips for the UFO and the thump thump sounds, plugged the board into the harness and turned the game on. The new power supply just goes into shut down almost instantly. So either the new power supply is bad or my game board has a dead short. I'm not sure what to do now..... Any ideas?