Re: Gottlieb System 1 power supply/transformer question

Congrats on your first game!

I wouldn't worry about your -12vdc, as the Ni-Wumpf only uses the +5vdc. There's something funky going on with your A2-P3 voltages though. I can't see how the +4vdc can reach 80v. That line is fed by the 5v line of the power supply. You may want to double check your readings. Also, make certain that you run a ground off of the power supply.

Before writing off your transformer, double check your 69vac readings at the transformer again. And to answer your question, the only component in the signal path between the transformer and the power supply on this line is a 1/4SB fuse.

Finding that transformer can be tough. You have to rely on others parting out Sys1 games. The odds of finding that transformer elsewhere will be slim. The problem being is what other real world application uses those particular voltage, outside of a Sys1 pinball machine?


terrencel@xxxxxxxxxxxxxx wrote:
Hello Fellow Pinballers,

I'm restoring my first machine right now. It is a Gottlieb Dragon SS.
I've been diligently following the System 1 repair guide at (thanks to whoever did that, it is great).

Of course the board had acid damage - I have already ordered a Ni-
Wumpf replacement.

So here's the situation. I actually removed all of the electronics
from the box so I could clean and repair the lower cabinet. I have now
reinstalled everything that belongs in the lower cabinet and have also
reinstalled the power pcb.

I re-pinned the entire wiring harness, as recommended (not fun) and I
replaced the C1 capacitor on the power board with a new 10,000 mfd 16
volt. Up to this point, everything I have done fits with what the
repair guide expects.

I just now got to the point of attaching the power board to the bottom
panel AC power system and I'm getting weird readings.

The bridge rectifiers tested out correctly according to the guide.

Here are the readings I got with my multimeter at the pins on the
power board:

A2-P1/J1 (bottom most power supply connector).

A2-P1 pin (11.5 volts AC) = 12.3 VAC
A2-P1 pin (11.5 volts AC) = 12.3 VAC

A2-P1 pin 4 (14 volts AC) = 14.8 VAC
A2-P1 pin 5 (14 volts AC) = 14.8 VAC

A2-P1 pin 6 (69 volts AC) = 38.9 VAC
A2-P1 pin 7 (69 volts AC) = 31.5 VAC

A2-P2/J2 (top most power supply connector).

A2-P2 pins 1,2 (+5 volts DC) = 5.1 VDC (trim pot works fine)
A2-P2 pin 6 (-12 volts DC) = -11.77 VDC

A2-P3/J3 (right edge of power supply board).

A2-P3 pin 1 (60 volts DC) = 13 VDC
A2-P3 pin 3 (42 volts DC) = 0 VDC
A2-P3 pin 7 (+4 volts DC) = 80 VDC
A2-P3 pin 8 (+8 volts DC) = 81 VDC

I'll ask the easy question first:

Is -11.77 VDC too far out of spec to safely operate an orignal system
1 board ? The guide says -11.9 VDC minimum. What about for the Ni-
Wumpf replacement board? I don't think it uses the -12V supply, but
haven't dug into the literature yet. If I need to get it within spec,
how would I do this?

Here's the hard question:

Is my little transformer fried? The 69 VAC drives the 60 VDC, 42VDC,
4VDC, and 8VDC signals, so I'm assuming the low input voltage is the
first problem to solve. Is there any component in the signal path
between the transformer and the power board input that could have
failed? I get the same VAC reading between ground and the 69 V fuse.

Are these transformers still easy to find? I've seen lots of posts of
people looking for one. Can a replacement transformer be purchased at
an electrical supply store?

Thanks for your input,