If the coil stays activated then burning up is exactly what will happen

If the transistor is shorted to ground, as soon as the board is powered up the associated coil activates. It starts smoking soon after that.

Don't over think it. The coil fried to protect the fuse.

Things don't always go according to plan.

LTG : )

This was my first assumption but I overthink everything and it took me a half hour to get all the documents together to answer the "Why?" Conflicting connection information in the specific game manual never helps either.

If you read my post and understood it you now know more than most pinball owners ever wanted to know.

TIL the slamramp is the 4th flipper. Never had to troubleshoot so never thought about it, but it makes sense based on game operation.

Not the first to do so however, JM uses 3rd and 4th flippers for diverters.

Interesting information along these same lines ... STTNG has no 4th flipper circuit connection but uses the Flipper 4 EOS switch circuit on the Fliptronics board for the spinner! How crazy is that?

Paging a Pinwiki editor. ForceFlow , ChrisHibler can we get https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Transistor_.22Quick_Check.22 updated?

I'm helping someone with a BSD where the right Mist gate won't stay open. Cycles up and down and sometimes blocks the ball from entering the right pocket. Throws lots of errors and disables normal Mist MB. Coil is driven by the Fliptronics board. Put in a known good Fliptronics board and the gate works perfectly.

Board looks fine, but I haven't dug into it. Borderline Tip102 or Tip36 is my guess. They don't always short to ground when they fail.

Two reasons come to mind.

1. All switches used in the (regular) 8x8 switch matrix.
2. Direct switch may have a slightly faster and consistent response than a switch in the matrix.

Indiana Jones center bank drop targets are direct switches. Leads me to concluded it's probably reason #1.

I believe there is a thread about the 100uF@100V capacitor. Williams removed it in later production of the boards (presumably to cut cost). The thread talks about installing the capacitor in Fliptronic board. The power board has one on the 50VDC that it generates. The Fliptronic board may or may not have it as the component is not always installed. If someone swapped the board from a later production game this may contribute to the problem (according to the thread).

Both are very good reasons and I would concur with option 1; without counting the EOS or direct ground switches STTNG has 69 switches.

I notice further down in the Pinwiki at https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Coil_Fails_to_Work
in paragraph 2 it says, “ With the game powered on, and a short length of wire stripped on both ends, touch one end of the wire to the ground braid in the head. Touch the other end of the wire BRIEFLY to the tab of the associated TIP-102. If the coil pulls in, then the path to ground has been proven and the failure is likely the TIP-102 itself. NOTE: This test can be performed ONLY when a TIP-102 is the drive transistor. TIP-36c transistors are configured differently. The tab of a TIP-36c is not connected in the same way internally.”

Might need a change there too?

Yes this should read "The tab of a TIP-36c is not connected in the same way externally."

This is very concerning as reversing the outside wires would forward bias both the primary and secondary flyback diodes all the time and your 50V is just just waiting for a path of destruction.

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Based on an assumption that WPC95 flipper control and WPC89 flipper control works the same way, as soon as the CPU activates the flipper coil, BOTH the Power and Hold transistors energize and would short your 50V right through both transistors to ground; this would allow a destructive amount of current to flow through these two components and may have causes some board damage. The destruction of the one coil diode shown in your picture is actually a good thing as it would have broke the short circuit by forcing the current to flow through the coil windings instead of around it.

You definitely want to either test and or replace both your drive your drive transistors, the best way to check this is as follows:

If the board is on your bench check for continuity between any ground point and on the board and to J120-4 and J120-6, continuity here would indicate a shorted transistor.

If the board is installed in the game you could perform the same test as above by removing J119 and J120 but you can use any ground point that's easy to access for checking between J120-4 and J120-6 to ground. If you do this check with the game powered on you should keep the coin door open or remove the 50V fuse as a precaution.

Thanks for the page @yeoldpinplayer, Acronymicon and @pin_guy.
I've updated/corrected the above two entrys.

I still have in the back of my mind that I need to review TIP-36c testing procedure. I had a discussion ages ago with terryb IIRC, about this.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

ChrisHibler Thank you for all your efforts in maintaining this page, it's a great resource for folks working on their pins and it provided with just the right amount of detail that most can understand it and also more detailed information for those of us that want this kind of information.

TerryB definitely has a different procedure for testing TIP-36c. I've found some chips that will pass the test shown on pinwiki using red on the center leg only, but others that don't. I believe TerryB's process is actually correct:

PNP transistors, left lead is base (i.e. – TIP36C and TIP42)*

Put the DMM’s black lead on the left leg of the transistor.
Test to the middle leg and the right leg with the red lead.
You should get a reading between .3 – .9 volts on each (the two reading should be about the same).
Put the red lead on the left leg of the transistor.
Test to the middle leg and the right leg with the black lead.
Your DMM should read open on each.
Test across the middle and right legs, you should get an open reading.
Reverse leads on the middle and right legs, you should get an open reading.

Ohms? Do you have a link to the procedure?