System 1 power supply question

alejandromad

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Game is completely dead... only GI works.

I saw the game working, minus the displays, when I purchased it.

Got it home and A2P1 basically fell off in my hands when I tried disconnecting the harness.

Bought a "working" power supply but before plugging it in I tested the voltage at the plug

Using pin 3 as the ground I read:

Pin 1 and Pin 2 - 12.5 VDC
Pin 4 and Pin 5 - 15 VDC
Pin 6 and Pin 7 - 75 VDC

I realize those are a little high (esp Pins 6/7) but not sure why or if that's a significant enough difference to cause my issue.

I read the pins on A2P2.

Using pin 5 as the ground I read:

Pin 1 and Pin 2 - something in the millivolt range
Pin 6 - neg (-) 12 VDC

Hmmmm... seems like a bad power supply.

Here's what worrisome to me... almost immediately the diodes CR1 and CR2 get hot enough to be untouchable and now, after taking voltage readings for maybe a grand total of 5 minutes combined, there is an ominous buzzing sound coming from A2.

I WOULD trace the voltage flow (using the schematic) but the buzzing is a little scary. I don't want any caps or diodes to pop in my face.

What's going on?
 
man hope you get to the source of the problem. I'am taking an electronic hands on course get get a little knowledge on this sort of thing. Good luck.
 
Game is completely dead... only GI works.

I saw the game working, minus the displays, when I purchased it.

Got it home and A2P1 basically fell off in my hands when I tried disconnecting the harness.

Bought a "working" power supply but before plugging it in I tested the voltage at the plug

Using pin 3 as the ground I read:

Pin 1 and Pin 2 - 12.5 VDC
Pin 4 and Pin 5 - 15 VDC
Pin 6 and Pin 7 - 75 VDC

I realize those are a little high (esp Pins 6/7) but not sure why or if that's a significant enough difference to cause my issue.

I read the pins on A2P2.

Using pin 5 as the ground I read:

Pin 1 and Pin 2 - something in the millivolt range
Pin 6 - neg (-) 12 VDC

Hmmmm... seems like a bad power supply.

Here's what worrisome to me... almost immediately the diodes CR1 and CR2 get hot enough to be untouchable and now, after taking voltage readings for maybe a grand total of 5 minutes combined, there is an ominous buzzing sound coming from A2.

I WOULD trace the voltage flow (using the schematic) but the buzzing is a little scary. I don't want any caps or diodes to pop in my face.

What's going on?


The input lines on P1 are AC signals so you cannot measure them with respect to ground.

The output pins --
your +5V line is shorted somewhere on your board. That explains the zero output voltage and the overheating diodes.
The -12V line looks good.

Is anything plugged into J2 or J3 while you are testing these voltages?

If so, unplug from them and see if you get the same results.
If nothing is plugged into J2 or J3 and the board is shorted then make sure the bit TO-3 transistor in the middle didn't get shifted on the heatsink and one of the pins is now against the heatsink. The power supply may have worked before being shipped but may have been whacked during shipping and moved the heatsink a hair.

Ed
 
Of course... you are right... the inputs on J1 are not DC... doh! I was measuring in the AC mode... sorry, that was silly. I switched it to measure J2.

... and when I did the measuring I did not have anything plugged except J1.
I should have stated that.

I will check the transistor as you mentioned.
Thanks!
 
The input lines on P1 are AC signals so you cannot measure them with respect to ground.

The output pins --
your +5V line is shorted somewhere on your board. That explains the zero output voltage and the overheating diodes.
The -12V line looks good.

Is anything plugged into J2 or J3 while you are testing these voltages?

If so, unplug from them and see if you get the same results.
If nothing is plugged into J2 or J3 and the board is shorted then make sure the bit TO-3 transistor in the middle didn't get shifted on the heatsink and one of the pins is now against the heatsink. The power supply may have worked before being shipped but may have been whacked during shipping and moved the heatsink a hair.

Ed

Let me just say it's great to have Ed posting here.
 
OK... I repaired the A2P1 connector that had basically fallen off the original power supply... measured the voltages at A2P2 and they looked good. I plugged up P2 and P3 and turned the game on. Yeah !!! I got to play Charlie's Angels !!!

As for the other power supply and the big old transistor on the bottom... it's not shorted to the heat sink so I don't know what to check next. I think I will send it back to the person I bought it from and maybe he can fix or replace it.

Thanks for the help Ed (and everyone else)
 

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Congrats on the fix! Charlie's Angels was my first pin. It is a pretty fun game. If it wasn't for that totally worthless top left "lane", it would be excellent.

Note: I quoted lane because all that ever happens when you shoot it up there is either: hard shot= violent airball, soft shot = drifts back down to sling for cross table hit.
 
Congrats on the fix! Charlie's Angels was my first pin. It is a pretty fun game. If it wasn't for that totally worthless top left "lane", it would be excellent.

No doubt... that left lane doesn't seem to be of much use. I checked out your CA restore thread even before I picked mine up. Nice work.
 
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