TSPP Flipper fuse popper

[Bigbloke]

Hi,

I only have one Stern, a TSPP, versus 4 B/W machines so I am less familiar with them. My TSPP has started blowing the fuse for the upper right flipper. As soon as the machine is switched on the flipper activates and pop goes another fuse. If I don't replace the fuse the machine all works bar this flipper, so I suspect the transistor drive. Before I have the hassle of removing the power driver board to swap the transistor(s) out, is there anything I can do to confirm this diagnosis?

Cheers,
Paul

 

[Calimori]

I would talke a look at the coil and check the wiring is correct and that the coil is looking healthy. You can check across the lugs and see if it matches the expect reason from another coil.
I would then dive straight to check the transistor.

 

[Moonraker]

Depends on the current path in the circuit but the fuse may have protected the transistor from blowing if the coil is the problem or vice-versa the fuse may have protected the coil if the transistor is blown if you're really unlucky and the fuse hasn't done it's job then both the coil and transistor will need replacing... First thing is to check the resistance across the coil lugs (as calimori says) and then go from there.

 

[Bigbloke]

Thanks guys. I have just been and measured the coil resistance. It is 5.2Ohm, however it is the only orange banded coil, so I can't compare with an exact match, a couple of the other coils measure 3.6Ohm and 4.5Ohm so it looks like it is in the right arena. I can't tell from just looking if the wiring looks ok, but it doesn't look any different to any other (and there are many on a TSPP) flipper. Now I just have to trace it the wiring back to the Power PCB and work out which tranny is being a b*gger! Not easy as I can barely squeeze down either side of the machine. Oh to have a proper games room!

 

[Moonraker]

The manual should tell you which transistor it is so you don't have to trace the wiring back...

 

[Bigbloke]

The manual should tell you which transistor it is so you don't have to trace the wiring back...

It certainly did! Q14 was the culprit. Seems it's already been changed at least once before, so I checked the coil, wiring and diodes again. Couldn't find a fault, so I changed the Q14 for one of Phil Palmer's finest alternatives, and much cussing later I have a working upper right flipper. Yay!

Now for the strip down, clean and rerubber! Oh what's that one more game first? Why not!

Thanks Guys!

 

[Wizcat]

The quick and dirty way to check for busted transistors is to see if they have permanent continuity to ground. You can do this with a meter set to continuity check, machine powered off. Then hold one probe against metal tab of the TIP102/120, and the other against ground (braid, or metal backplane in the backbox). If the transistor has permanent ground then its busted, and would behave exactly like you saw.

This only works on TIP102/120's though. The larger TIP42s that BW games use for flipper control can't be tested like this.

 

[pinballmania]

Thanks guys. I have just been and measured the coil resistance. It is 5.2Ohm, however it is the only orange banded coil, so I can't compare with an exact match, a couple of the other coils measure 3.6Ohm and 4.5Ohm so it looks like it is in the right arena. I can't tell from just looking if the wiring looks ok, but it doesn't look any different to any other (and there are many on a TSPP) flipper. Now I just have to trace it the wiring back to the Power PCB and work out which tranny is being a b*gger! Not easy as I can barely squeeze down either side of the machine. Oh to have a proper games room!

The resistance is ok. But you MUST check that the diode is intact and the leads are not broken. If the diode is broken the flipper may stick up even when the transistor is good.