(Topic ID: 344272)

T2 Flashers lock on

By Don44

9 months ago

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#1 9 months ago

I was working on the drop target switch and the coil wire came loose and I hooked it back up. Now when I power on, none of the coils work and the flashers stay locked on and the cannon runs constantly. The fuse had blown and it blows when I replace it. Any suggestions?

#2 9 months ago
Quoted from Don44:

the coil wire came loose and I hooked it back up.

Hooked it back up in the right spot ?

LTG : )

#3 9 months ago

I hooked it back up like it was but I realize now was wrong. It was not working and I didn’t realize there was a third wire and I think I may have fried something. I put the thinner purple wire on the right lug

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#4 9 months ago

My guess is that some thing is fried on the power driver board. I unhooked J122, that is the connector in the manual associated with the drop target and flashers. The flashers still stay on though so I’m confused

#5 9 months ago

In general, if you turn the game on and before the game even boots a coil or a flasher locks on, you've got a blown transistor.

Here is the manual for your game:


On PDF page 2 (inside the front cover), there is a chart of coils and flashlamps.

If, for instance, it's your gun flashlamps that are locked on, the chart says Q26. Pull your WPC driver board, and use a meter on Q26, it'll probably read shorted.

A TIP102 is a great replacement transistor. On earlier boards you might have a stronger possibility that the 'pre driver' transistor would be shorted... but WPC games usually just blow the first transistor in line, the TIP102. Still, you can measure the small transistors around the TIP102 that you are interested in, and they should read the same as the identical circuits around them. Do this after you've pulled the shorted TIP102, because a direct short in that transistor can affect your readings of the 'pre driver' connected to it.

#6 9 months ago

There was a fried resistor, R25. I replaced that resistor and another one near it, as well as the diode and the transistor right near it as well. The coil that initially caused problems is not hooked up. When I power on it blows fuse 105.

#7 9 months ago

Fuse 105 blowing instantly.

In your book, pdf page 112, it shows that everything associated with Fuse 105 is pin 3 on J107, the Violet-Yellow wire.

These are solenoids 1-8 in the table on pdf page 2.

All of these get ground path (are switched on and off by transistors) at J130.

For grins, disconnect J130, turn on the game, make sure that the fuse doesn't blow.

In WPC systems, J107 (where the fat Violet-Yellow wire gets it's power from...) is also connected to J106 and J108. There is one spot on the WPC driver board, where the connectors are keyed in such a way that you can plug the wrong thing in... and it's possible to stretch the wire from what should be plugged at J124, and plug it into J106.

J106 should only have one wire, red, that goes to the flashlamps in the backbox. J108 should be empty.

It would be rare, but possible, to have the wrong thing plugged in here. (Very remote possibility, but I've seen it happen!)

So, if the fuse doesn't blow with J130 disconnected, you know your problem is one of those eight coils, and their associated driver transistors.

Pull the power driver board, and go down the line of Q70, Q68, Q66, Q64, Q76, Q78, Q80, Q82. All of these identical circuits should read identically.
Then I'd go to the predrivers for these: Q69, Q67, Q65, Q63, Q75, Q77, Q79, Q81. All of these identical circuits should read identically. Continue with the small transistor predrivers. Same procedure.

You are looking for the shorted transistor that is providing a path to ground.

The usual path is that you've popped the transistor because the associated coil is shorted, or it's diode is shorted (I don't seem to find this nearly as often as other technicians do...).

So the usual path is to examine the coil associated with the popped transistor. Any hint of browned wrapper and you'll replace the coil. You can also unplug J130 and measure resistance across the coil. Less than 2 ohms is bad, 4 ohms plus is good. The coil should be reading the same as other similar coils (the knocker and the ball popper are both 23-800's, so they should have very similar resistances). Any questionable reading here and you replace the coil. Sometimes the coil reads fine, it was just the transistor causing the problem.

You are popping the fuse because your Violet-Yellow fat wire on J107 pin 3 is being connected directly to ground. This is nearly always because a transistor is shorted and is providing a path to ground. Replacing the transistor and getting it's associated circuit to read identical to the similar circuits in the line is the first step. The second step is to make sure the coil attached to that transistor isn't going to blow the transistor again, whether it's because of shorted coil (common) or shorted diode (common for other technicians), or miswiring.

Let us know what you find.

#8 9 months ago

To rehash everything so far I was fixing the switch on the drop target assembly and a wire came loose from the coil. I didn’t realize, but there was a wire that already was not connected, and I thought the loose wire went to the other lug. I just got the machine and I guess the green wire was what actually came off and the other thin violet orange wire was not attached. I had the thick violet orange wire on one side and the thin violet orange wire on the other. This caused a resistor on the board to fry, r25. I replaced this resistor and also replaced r 23 Q1 R 24 and Q 20 transistor.

I also tested all of the other transistors suggested, and none of them was shorted. I am still experiencing the same problem with the flashers coming on and some coils locking on. I appreciate all the help so far but I think I may have to send the board out, although still open to suggestions.

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#9 9 months ago


This is presenting as two different problems. Flashlamps, and coils.

The driver chips for the coil bank and the flashlamp bank are not commonly connected except through the data buss, and if (for example) Data line D3 was compromised, I'd expect you to have other problems with lamps as well as coils and flashlamps.

A skilled board technician would likely make short work out of this problem.

This is fixable, but it's a bit more challenging than the usual 'you blew the output transistor'.

Let us know if you are going to tackle this yourself.

And if you are going to tackle this yourself, we'd need to know:

Do coils and flashlamps immediately lock on when power is first applied, before the game starts?

Which coils, which flashlamps?

Does a fuse blow immediately when power is applied? Is this fuse F105 (coils)? Does fuse F105 (coils) still blow immediately on power up when J130 (connection to coils) is removed?

Are there other fuses blowing? Which?

Are there other symptoms like a string of lights or single bulbs being lit up immediately upon power up?

You've made some solder connections under the playfield. Do you still get things blowing fuses and having problems when you undo your solder connections (disconnect those wires again?)

This is far from easy stuff, and I'm sorry you are going through this.

1 month later
#10 7 months ago

I sent out the MPU and power driver board to be fixed and tested. When I power on it blows F111 and F112 and F105. The box where the power goes in does not have a fuse, so it must be hacked. Could this cause issues as well. Just making sure I have the two coils wired right as well.

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#11 7 months ago

that plunger in the last pic doesn't look correct being on an angle.

thinking the adjustment screw on the underside may need to be screwed in/up to prevent the plunger from being out so far?

1 month later
#12 6 months ago

I wound up sending the board out and had the machine working properly without blowing any fuses. I had to adjust a switch under the playfield, and after doing that it blew fuse JF112 when I started the machine up. after that I wound up rebuilding the power box because it was hacked. All worked again for a while but now blowing fuse F112 again. Any idea of what I might be overlooking?

#13 5 months ago

Blowing F112.

F112 is your 50v circuit.

Replace the fuse. Pull J107 (middle of the board). If J106 or J109 has something plugged into it, pull that too, for testing.

Power on.

If the fuse blows, you likely have a bad BR3 bridge rectifier.

If the fuse doesn't blow, you have a 50v coil problem somewhere on the playfield.

Let us know what you find.

#14 5 months ago

Sounds like a ribbon cable plugged in one row off causing the J112 to blow.

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