(Topic ID: 159008)

WOZ fuse 706 keeps blowing and I'm out of ideas-help!

By WesleyCowan

7 years ago


Topic Heartbeat

Topic Stats

  • 19 posts
  • 7 Pinsiders participating
  • Latest reply 7 years ago by Crash
  • Topic is favorited by 2 Pinsiders

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#1 7 years ago

Was playing WOZ last night and noticed a spark coming from the ball plunger area. It was coming from the coil that is connected to the autoplunger. Discovered the coil looked partially burned and very carefully replaced it making sure to mark and takes notes on all the connectors on the coils and trough area and did this carefully and slowly being very detailed not to make mistakes. I also took the trough off to make sure a nut or something else hadn't fallen in jamming that area.. Made sure the plunger inside the new coil was moving freely with no binding or problems..
Anyway, every time I turn the game on the 706 fuse now blows immediately. I've gone and over and over my every bit of my work both last night and tonight including looking at every wire, connector, etc. Read the manual and went through every coil that fuse 706 controls. No problems found and noe of them cause it to blow only reconnecting the autoplunger coil cause it. Tried another coil and that didn't help. Have looked for foreign objects, metal etc around the coil, trough, autoplunger and even on the boards since I've been in that area replacing the fuse. I've googled but nothing I've found so far has been a solution.
Help please I'm all out of ideas, tied, and frustrated!

#2 7 years ago

Q323 , it's transistor might be bad.

LTG : )

#3 7 years ago

Thanks Lloyd I'll check that.

#4 7 years ago
Quoted from WesleyCowan:

Was playing WOZ last night and noticed a spark coming from the ball plunger area. It was coming from the coil that is connected to the autoplunger. Discovered the coil looked partially burned and very carefully replaced it making sure to mark and takes notes on all the connectors on the coils and trough area and did this carefully and slowly being very detailed not to make mistakes. I also took the trough off to make sure a nut or something else hadn't fallen in jamming that area.. Made sure the plunger inside the new coil was moving freely with no binding or problems..
Anyway, every time I turn the game on the 706 fuse now blows immediately. I've gone and over and over my every bit of my work both last night and tonight including looking at every wire, connector, etc. Read the manual and went through every coil that fuse 706 controls. No problems found and noe of them cause it to blow only reconnecting the autoplunger coil cause it. Tried another coil and that didn't help. Have looked for foreign objects, metal etc around the coil, trough, autoplunger and even on the boards since I've been in that area replacing the fuse. I've googled but nothing I've found so far has been a solution.
Help please I'm all out of ideas, tied, and frustrated!

Wes,

I had a similar issue with my TZ a few years ago on the shooter lane coil. Check the wiring very carefully for this coil. I had a single loose wire strand that was contacting an adjacent piece of metal and causing a short every time the machine tried to auto-plunge a ball.

I realize that this is for a WOZ, but your issue sounds very similar to the type of issue that I had on my TZ with the auto-plunge coil.

Gord

#5 7 years ago

Duplicate Post

#6 7 years ago

Mine did this. I sent the board back to JJP and they repaired it for about $85. I also replaced the burnt coil. A good idea to get some extra fuses too.

#7 7 years ago

Why would the MOSFET fail in just a couple of years time? I've heard these were beefed up beyond your typical TIP102.

#8 7 years ago
Quoted from Crash:

Why would the MOSFET fail in just a couple of years time? I've heard these were beefed up beyond your typical TIP102.

I'm not sure but my problem started since new. A mislocated coil wire was hitting the coil plunger. Eventually when the plunger fired the game would shut off. This may have weakened the transistor. Later the slipper broke off and players kept playing.(I was not around to fix immediately). My guess is the piece of flipper jammed the trough and the coil kept firing then overheated the coil or the transistor just gave up.

#9 7 years ago

Gotchya, he did say he saw a spark.

#10 7 years ago

Are there diodes on the coil you replaced? If so you likely wired the coil to the incorrect diode orientation. That would have taken our the MOSFET on the board, and in turn the shorted MOSFET took out the coil diode.

A coil diode can be put across the coil lugs in either direction, the coil doesn't care, it's wiring to the diode that matters, not the coil lugs. The power side wiring always goes to the diode's cathode, the banded side of the diode. Which leaves the drive side (usually the thinner wire) goes to the anode of the diode, the non-banded side of the diode.

If this is the case, both the driver transistor and coil diode will need to be replaced at the same time, before powering on again. Failure to do this will continue to take out one or the other on each power up.

--
Rob Anthony
Pinball Classics
http://LockWhenLit.com
Quality Board Work - In Home Service
borygard at gmail dot com

#12 7 years ago

Holy triple posting Batman!!! Someone stop the madness and chop off my fingers!!

--
Rob Anthony
Pinball Classics
http://LockWhenLit.com
Quality Board Work - In Home Service
borygard at gmail dot com

#13 7 years ago

I did have to put a diode on the new coil but through past mistakes I know it's vital re: the banding orientation. However, good to be mindful of that as I proceed. Thanks!
I'm heading downstairs to look at and test the transistor and bringing my laptop down with the very helpful suggestions and thoughts expressed so far. I'm planning to go slow as I don't want to mess up and end up with potentially complex board or other issues.

Thanks to everyone who has responded so far!

#14 7 years ago
Quoted from Crash:

Why would the MOSFET fail

Crap happens. Stern has had same problem with 22NE10's in the past on flippers.

I don't know if it's cheaper transistors or what out there. But it happens.

LTG : )

#15 7 years ago
#17 7 years ago

#18 7 years ago
Quoted from LTG:

Q323 , it's transistor might be bad.
LTG : )

LTG nailed it. Replaced it and WOZ is once again working great. Thanks again for everyone's suggestions!

#19 7 years ago

Easy fix! Enjoy your game.

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