TZ Tripping Circuit and Fried Thermistor

Michael Roma

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I just picked up a non-working TZ on CL and have a question regarding the powerbox.

After I got the game home and unloaded I did the precursory checks, I powered it up. Immediately I heard a low gutteral sound and then nothing. The circuit that the pin was plugged into tripped and when I lifted the playfield I noticed smoke coming from the power box.

I unplugged the game and removed the power box to see that the thermistor was fried and the inline fuse was bypassed.

This is a re-import from Germany. Has anyone seen this behavior before or have any knowledge on the cause? Thanks.

- Mike

tz_powerbox.jpg
 
Do some searching on the RGP forum for info on converting re-imports. Or just start a thread there. I found info there on converting re-imports when I got my Dirty Harry, which was a re-import from Germany. Mine worked fine, but I wanted to verify that it was converted correctly.
 
This was already converted and working on US 120V from what I was told by the previous owner (they had it in their house for 5+ years). I will check RGP to confirm the conversion settings are indeed correct.

- Mike
 
It's a varistor, or MOV RadioShack sells suitable replacement last I knew. Replace the MOV, rewire the fuse, confirm power wiring... Should be good to go.
 
I believe the one that comes off the fuse hold to the line filter is a thermistor and NOT a varistor. Can someone else confirm?

What would cause this to fry like it did?

- Mike
 
I believe the one that comes off the fuse hold to the line filter is a thermistor and NOT a varistor. Can someone else confirm?

What would cause this to fry like it did?

- Mike

Yes, that's the thermistor. The other disc thing in your picture (soldered to the two legs of the line filter) is your varistor. You might want to check it too....and make sure it's not shorted.

Edward
 
I have replacement thermistors and varistors on order.

I was planning on:

- fixing the fuse holder and putting an 8A fuse in it
- replacing the varistor and thermistor
- disconnecting the transformer and then powering on

If it powers up w/o blowing the line fuse I would then:

- turn the game off and disconnect the connectors going to the boards from the transformer
- plug the line assembly box to the transformer and then power on

I am hoping that this will determine if the problem is with the transformer or the line filter.

Is my logic sound? Also, is there a way to test the line filter? Where can a replacement line filter be found?

Thanks in advance...

- Mike
 
I replaced the fuse holder, thermistor, and varistor today. I plugged the power assembly in outside the game while I had it on my test bench and everything looked good (120V AC).

I plugged the transformer up and disconnected all connectors going to the pcbs. When i plugged it in the 8 amp fuse in the power assembly box blew.

I guess it I am looking at a transformer issue... Right? Is there anything I can do to the existing one or do I need to find a replacement? Thanks.

- Mike
 
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Transformers usually don't go bad, but it's possible the pin was hit by a power spike/lightning and it got damaged..
don't have any experience troubleshooting transformers so can't help you more with that.
 
I just confirmed it is the transformer. I pulled the transformer from my Judge Dredd and put it in the TZ and now it powers up.

It resets and the DMD has vertical lines but it is now showing signs of life.

Now to start troubleshooting these new issues.

- Mike
 
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