Williams Stargate arcade. Where's my +12v?

mitchschaft

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Working on a new project, after installing BR's cap kits, replacing headers, installing a PS rebuild kit, including the 2 IC's and the 2N6059. I go to power it up after getting hold of a known-good power supply and F3 pops right away leaving the second LED for +12v not lit.

I realized I had a cap in backwards on the soundboard (the black one in the middle, top right) when I heard a hissing. I installed it the right way hoping no fuses would pop, but F3 did again. So that's when I disconnected the boards from power all together.

I've been reading through threads and think I may have narrowed it down, but need some more direction. I did Dokert's tutorial on reading bridges and BR2 likes to beep at me with my multimeter. So I figured I will replace that.

I did some measurements across the 2n6059 transistor's 1&3 pins, I get 9.86 if I did it right.

From fuses F5 and F4 I get 22.2v. TP4 I get 4.95, TP5 is 14.83 and the other TP5 is 15.20. I couldn't find a TP1 so I figured what I read might be for another power supply, maybe defender.

So now my head is spinning. Aside from replacing the recitifers, what else should I test? Or any other advice.
 

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Hang in there. I'm no repair guy, but even I found the schematic not too bad to follow. After doing the rebuild kit, I had a voltage out (can't remember which). It actually turned out that the big cap wasn't making a connection from the top to bottom of the via. Good solder joint and all..I had to replace the cap, put it 1/4" above the board instead of flush, then solder top and bottom of PCB. I figured that out by following the missing voltage to that cap.
 
yeah, I can't see why after installing all new components that you would be missing a voltage outside of some kind of installation error. lol

it's pretty easy to mess that sort of thing up. when I did my Defender power supply I stripped that thing completely bare, washed it with simple green, the whole shot, and redid EVERY solder joint on it. I was such an asshole about it that it actually fired up correctly on the first try.
 
TP5 is 12VDC unregulated....this is the TP5 beside the big yellow/orange axial cap. The other TP5 (by the bridge) is an error. It's supposed to be TP6. Your circuit board was printed incorrectly. TP6 should be -12VDC unregulated. If you had a positive reading there...that's not correct. If you install a cap backwards and power up the machine.....that cap is suspect, at best. Since you stated it made a "sizzle" sound, it's bad. That cap is in line with F3 (after the bridge).

Edward
 
Do you think the backwards cap blew the bridge and that's why the fuse keeps popping even after the soundboard isn't even hooked up? That makes sense to me.
 
I see, I think mr lutz was talking about the C14 cap next to the F3 fuse. The cap that hissed at me is on the soundboard next to the power supply board.

I had to dig up a Moon Patrol scheme for this power supply since the one in my Stargate drawings are the old defender type.
 
The caps on the power supply pictured are installed correctly as far as polarity goes.

F3 controls +/- 12vdc reg

If F3 pops immediately and BR2 tests good, suspect the 2N3055 or IC1. IC1 is the most probable, as most people tear up the traces when they install the socket and remove the old regulator chip.
 
Oops, I hope i didn't tear it up. I'll check that out. And I think BR2 failed since it keeps beeping at me when I use the diode check. The number shoots way high, too.
 
I took it out and here's what I get:

negative lead to AC = 472, second leg beeps

positive lead to AC = 494, 487

BR1 screams at me in circuit on a couple legs and also jumps to 1,300 or so.
BR3 test out fine.
 
BR2 is bad replace it.

Pull BR1 and test it out of circuit.



I took it out and here's what I get:

negative lead to AC = 472, second leg beeps

positive lead to AC = 494, 487

BR1 screams at me in circuit on a couple legs and also jumps to 1,300 or so.
BR3 test out fine.
 
Make sure you put BR2 back in the correct way. If it is put in backwards it will blow the fuse immediately.

Also when you replace BR1, it is a good idea to solder the top of the pads as well. The plated through holes tend to get damaged and the top pads don't always have enough connectivity to carry the current required. The +5V will show as +5V when it doesn't have a load and then it will drop when the boards are plugged in.

ken
 
Thanks for the tips. I'm gonna order a BR2 and a BR1 for good measure. I also reinstalled the 2 IC sockets and made sure to get some solder on the top pads so those look much better than before.

Here's something I did find. It looks like these 2 resistors were cut out. W2 and W3. Can't find it in the bill of materials so I don't think it's supposed to be there.
 

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The two missing zero ohm resistors are used for cocktail games only and should not be there. They are documented in the Joust scat only from what I recall off of the top of my head.
 
My Bob Roberts order came in. But I forgot to order the damn BR2, the whole reason for placing the order :(. kbu401. I'm gonna try to find a source with cheaper shipping for that one part.
 
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