(Topic ID: 243272)

Question. Should all of my playfield coils be shorted together?

By StotzBotz

2 years ago



Topic Stats

  • 9 posts
  • 5 Pinsiders participating
  • Latest reply 2 years ago by chad
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#1 2 years ago

I've been trying to figure out why on my Williams Flash machine why certain coils aren't firing. When I use a voltmeter all of my drop target coils and ball reset coil appear to be shorted together. I am burning up a drive transistor to one of the drop targets which is solenoid #4 and Q21. Should all of these coils be connected in some way to one another? I'm thinking this is where my problem is but hoped someone could help me figure it out. All of the drop target coils were replaced by the previous owner. I know the ball reset diode is not shorted but haven't checked any others yet.

#2 2 years ago

You will have 8 coils in a row or column. Make sure you change out the driver transistor and the pre driver . Also the diode on the suspect coil is bad. If it still is not working you may have a 74xx chip bad on driver board, or further up the chain , 6821 pia chip.

#3 2 years ago

The biggest issue with these older William's games is the 40 pin interconnect. It causes many issues including locking on coils. Its it hasn't been changed I'd always start there.

Also if replacing it always replace both the male and female side, not just one.

Mitch

#4 2 years ago

When you say shorted together are you referring to the power side? The power is usually daisychained coil to coil, at least for ones that are close together.

Compare the resistance across the individual coils, you may have one shorted out causing the problem if you're repeatedly blowing that transistor.

#5 2 years ago
Quoted from Mitch:

The biggest issue with these older William's games is the 40 pin interconnect. It causes many issues including locking on coils. Its it hasn't been changed I'd always start there.
Also if replacing it always replace both the male and female side, not just one.
Mitch

+1

#6 2 years ago

OK so first of all thanks everyone. The diode is shorted across the coil that has the driver transistor frying. Just wondering if this would cause the other coils not to fire. I did check the pre driver transistors and none of them seem to be shorted at any of their pins and seem to read the same resistance. I was going to replace the driver transistor and diode and see what happens and in the mean time order some of the pre driver transistors. This game does have a new motherboard by the way.

#7 2 years ago

Yes, all the coils are connected together, that's how they get power.

They are individually grounded by a transistor on the driver board, that's how each one fires on its own.

A shorted diode on one coil will cause the others not to work if it blows the fuse. Games like Flash have a single 2.5A slow blow fuse on the power supply that controls all the playfield coils. If it is burned out, you'll get nothing.

#8 2 years ago

I think the under playfield fuse is 1a slo blo right? Could also be the cause. Not at a game right now that's just from memory.

#9 2 years ago
Quoted from Chalkey:

I think the under playfield fuse is 1a slo blo right? Could also be the cause. Not at a game right now that's just from memory.

Bally has the 1 amp fuse under field.

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