Space Invaders Deluxe Power Supply - Fail

orion3311

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Ok I'm tinkering with an SI-Deluxe kit I got untested from Wu. (I assumed it would need work no big deal).

Anyhow - thankfully before I plugged the board in I tested the power supply. Found -5v dead, +12 is really almost 12.2, and the +5v seems to bounce between 9 and 11volts.

That said, I then realized the +12v fuse on the power brick blew. Replaced it, and it blew again.

Here's the kicker/question - there's a bunch of diodes near the harness plug. For some reason, my meter is reading ALL of them except for 2 as OPEN. Does that make sense? The two in the corner which looked baked are reading shorted. Does that sound like my meter may be acting up? Its a nice Fluke so I doubt it, but damn I can't get ANY of the diodes to register ANYTHING either way, just seems wierd. Is it really possible this PS is epic fail, even though it sorta worked?
 
Good point, but I think I quit for tonight. Too tired. BTW I still have your brackets, I gotta get a tube or something to box them with. I hit the ups store and they didn't have any that were the right size, so I didn't forget about ya.
 
Awesome man, No sweat.
Thanks!

Good point, but I think I quit for tonight. Too tired. BTW I still have your brackets, I gotta get a tube or something to box them with. I hit the ups store and they didn't have any that were the right size, so I didn't forget about ya.
 
Dude, I have no clue how to fix that crap. lol
But fellow member oregonarcade has my old, working power supply at his shop if you're screwed. I think the harness is still attached to it as well. Shipping from Oregon would suck I'm sure, but you know, just thought I'd throw that out there.
 
When mine was acting up i decided to rebuild the whole thing.Total was about 35 bucks,but i replaced all the transistors,diodes and caps.The diodes were fine,but they looked scary old lol,so figured while i was in there.I ordered as much as i could from mouser on the transistor and diodes,then went to bob roberts for what mouser didnt have and the cap kit.Voltages are great now,except my -5v only goes as low as -5.06 v.
At one point i was also blowing the 12v fuse,but in my case it was a shorted cap on the sound board.
good luck to you
 
Question on the diodes - these 4 diodes, two of which I identified as being shorted (and baked), they're round. BrentRadio's site shows 2 seperate schematics, one having some odd diodes which I believe are the ones I have (with a number like A14-xxxx), and another showing 1n4004's. Would it be a safe bet to replace the ones I have with 1n4004's, of which I happen to have a few?
 
Still curious but I found out its a moot point anyway. Those diodes do nothing more than feed the lamps which are non-existent at the moment.

Found a cleaner scan of the layout and schematic here (same power board)...
http://arcarc.xmission.com/archive/..._II_Parts_and_Operating_Manual_(Oct_1979).pdf

I guess that explains why it seemed like everything worked without that fuse being good. That said - why did they use special diodes for an led?
 
Looking at the schematics, it looks as it's also used for audio circuits.

Also, I'd substitute an A14 diode with a 5400 series (1N5400, 1N5401, 1N5402, etc.).

Edward
 
Ok went back and reviewed what I have. I have no -5, but I have -14v to the regulator, and there's practically nothing else involved so I believe that reg might be bad. The adjustment pot works and adjusts the regulator to ground. The diodes that seemed to be open are working fine - AC to DC. If you go to the schematic in the above link, the two bad diodes are the two that are the uppermost left corner.

12v looks good enough to me at 12.11 volts. Adjust ok with the knob.

5v is putting out 10.0 volts on the money. Does not adjust with the pot. Could it be because the board isn't connected? Either way I'm not hooking it up until I can test with some kinda load (need a 10w resistor to test).

Or I can just buy a new power supply from TNT for $30 or use a switcher, but whats the fun in that?? :)
 
You definitely need a load to test/adjust +5V.

DogP
 
Just figured that out - put a light bulb on the 5v line and now it works and looks great. Still have no -5v though, and who knows where I"m gonna find that reg at. I have a tv hooked up but nothing showed up - yet.
 
I used a PC power supply to generate the -5v, and got a scrambled mess on the screen. Did some poking around and found at least a half-dozen broken or folded over legs between the rom chips and the processor. The processor had one bent pin I was able to straighten out. The roms are in bad shape - I cleaned up the legs but there's 4-5 broken legs. Tried to use resistor legs just wedged in but no go.

That said after reading the Brentradio page, I popped out all the roms, and get a nice clean screen with vertical bars, some thick some thin, so with any luck, a new rom set, -5v reg, and away it goes!!
 
So I got a new -5v regulator for the power supply and its 99% working again. Now these A14 and A15 diodes, can someone learn me on those? Bob has a couple midway ps layouts on his site and mentions to replace the diodes in that area with 1n5400s. Do I really need 3 amp diodes to run a few lights?

OldSupply.jpg


The diodes in question are lower left corner. From the schematic all they do is run the lighting - panel lights (cocktail) and coin door lights.
 
Bob has a couple midway ps layouts on his site and mentions to replace the diodes in that area with 1n5400s. Do I really need 3 amp diodes to run a few lights?

The diodes in question are lower left corner. From the schematic all they do is run the lighting - panel lights (cocktail) and coin door lights.

An A14 diode can be replaced with a 1N4007. An A15 diode should be replaced with a 5400 series (as Bob states.....and I said in the middle of this thread). These diodes have nothing to do with the coin door & cocktail panel lights. Those lights are fed straight AC voltage off the transformer. These diodes feed the audio circuits (which I also mentioned).

Edward
 
Sorry you did mention that. What I'm curious about is the part #s on the diodes - if I were to come across this in the future, how to I cross reference them? Couldn't find anything in my ancient ECG book and Google was no help.
 
IIRC, the "A" series diodes were made by General Electric. To my knowledge, they haven't made componets in years. Back in the late 70's.....there wasn't much standardization amongst semiconductor manufacturers regarding part numbers. Two different manufacturers would make the same part, but give it their own part number. A 1N4007 is a modern equivalent/substitute for the A14F diode.......as is the 1N5400 for the A15F. If you want originals....you're gonna have to search surplus houses.

http://www.datasheetarchive.com/
Here's a good site for comparing data sheets....they sometimes list substitutes.....and links to suppliers.

Oh yeah, NTE/ECG crosses....A14 = NTE125.....A15 = NTE5800

Edward
 
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Thanks - I was just curious like learning that stuff.

Radio shack had 1N5400's so if the legs fit I'll replace the A14s with those for now. I need a rom set and have bigger fish to fry so I might also just let it sit until I do another Digikey order.
 
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