Police force fuse F1 keeps blowing

[infinite1977]

Thought i would start a new thread on this issue as i am at a loss.
I have fuse F1 on the power supply board constantly blowing as soon as i turn the  machine on. I have isolated the  issue  to the  j3 connector. With everything  else off on the board, as soon as i plug this  connector F1 blows!!

[Pintoxicated]

What does the J3 connector run?  First thoughts would be that something is shorting out somewhere causing the fuse to blow.  Lights or coils - look for loose wires touching metal or coil tab touching some metal.

[infinite1977]

J3 wires run to the transformer according to manual. Everything  else works. There  are no loose wires on lights  now and fairly certain nothing  shorting on coils. Tested all coils with dmm and all are good  also.
Waiting for a new batch of fuses to come as i ran out and it is a wierd fuse 3/8a, now that lights have been redone

[Steevsee]

J3 brings power from the transformer to the board.

If the fuse is blowing with nothing else connected, there may be a short in the high voltage section.
Might be worth testing the transistors (Q1-4).

[infinite1977]

Thanks Steevesee how do i test these:)

[Steevsee]

Thanks Steevesee how do i test these:)

Pretty simple of you have a multimeter with a diode test function.

Set meter to diode test, pinball power off.
Connect your black lead to the Base of the transistor you want to test.
Now probe the Emitter and then the Collector.  Note your readings.

Next reverse the procedure by starting with the red lead connected to the Base.

Note any readings which differ between similar transistor pairs.

[Steevsee]

Also before you start, you should be able to isolate which side of the high voltage circuit is at fault by removing fuses F2(+volts) or F3(-volts). If F1 doesn't blow with one of these removed, at least you know which side to check.
I'd start removing F2 to see if F1 still blows.

[infinite1977]

Cool will report back. Do you know by any chance what Fuse f1 does?

[beaky]

Cool will report back. Do you know by any chance what Fuse f1 does?

F1 is the input fuse for the high voltage section for the displays.
before you replace the fuse unplug J2 and see if the fuse blows again.
if it does then the problem is in the HV section.

As long as F2 and F3 (+100v and -100v outputs) are the correct value if F1 blows then the fault will be a faulty component or components in the HV section

If you intend to use led displays then just leave the fuse out as the high voltage section is not needed for LED score displays
 

[infinite1977]

Thanks Beaky, i was thinking about you and was going  to contact you.
Hope all is well

[andypinboy]

Check that one of the cops isn't shooting the fuse while his partner is checking there are no witnesses around 

[infinite1977]

Ok fuse still  blows with no fuse in f2 and f3. Also with only just J3 connected on powerboard it blows.
Will have to take board to get rebuilt by the looks of things