(Topic ID: 147956)

Bally High Voltage won't adjust

By jwilson

6 years ago

Topic Stats

  • 10 posts
  • 7 Pinsiders participating
  • Latest reply 5 years ago by barakandl
  • Topic is favorited by 4 Pinsiders


Linked Games

  • Meteor Stern Electronics, 1979
#1 6 years ago

I've rebuilt the HV section on my power supply but no matter where I set the pot, it's always 230V. I checked the pot and it changes resistance when I turn it.

Also, this board is missing R53, which I can't find on the schematics at all. It's a later Stern board with the well-labeled layout. The displays work fine but I'd like to turn the voltage down to save them.

#2 6 years ago

DId you change all the HV section parts?

2N3584 transistor at Q21 (250 volts, 2 amp, TO-66 NPN).
(2) 2N3440 transistors at Q22, Q23 (250 volts, 1 amp, TO-39 NPN).
1N5275A zener diode at VR1 (140 volts, 1 watt).
1N4004 diode at CR21 (400PIV, 1 amp).
3/16 amp fast blow fuse at F1.
22k ohm 1/2 watt resistor at R51.
1.2k ohm 1/4 watt resistor at R55.
82k ohm 1/2 watt resistor at R56.
8.2k ohm 1/4 watt resistor at R54.
390 ohm 1/4 watt resistor at R52.
100k ohm 1 watt resistor at R35.
(2) .01 mfd 400 vdc metal polyester capacitors at C27, C28.
25k ohm potentiometer PC mount at RT1

#3 6 years ago

Check cr21 for being shorted. Possibly q21 shorted.

#5 6 years ago

The only other thing I can think of is to verify the pot is installed correctly. I've seen folks mistakenly install a pc mount pot 90 degrees off. You'll see the resistance adjust when you measure it, but it won't have the desired effect on the circuit.

If you really get stuck there are some Bally experts out here that might be able to look at your board.

4 months later
#6 5 years ago

I have the same problem,do you find a solution?

#7 5 years ago

Are you measuring TP4 or TP2?

230 is bang on for one of these

#8 5 years ago

tip 2

#9 5 years ago

Broken foil trace?

#10 5 years ago

If the pot does not adjust the high voltage and the HV IN = HV OUT. The transistors in the HV section are shorted. Probably all three of them. You can be guaranteed the transistors are bad if the 82k or 22k resistor (i forget which one now) is burnt.

I put together HV rebuild kits for Bally Driver games. I made about 25 of them, i need to figure out the price point and put them on my website.

I fix these driver boards too.

Thank you

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