(Topic ID: 6227)

Need help w/ STTNG

By Silverballer

9 years ago

Topic Stats

  • 30 posts
  • 10 Pinsiders participating
  • Latest reply 7 years ago by Atomicboy
  • Topic is favorited by 13 Pinsiders


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STTNG Drop target coils 001.jpg

#1 9 years ago

The drop target appeared to stop working on STTNG and as it is now when it tries to load up the balls it will launch the first and it drops under the borg ship and ejects out of the left vuk and then drains. repeats this consistently. Tests indicated that the drop up and down were not working, nor could I hear anything for the under playfield diverters. When I raised the playfield I instantly noticed this cherry switch leaf bent, which I am guessing might be the issue. I cannot determine if the leaf just got caught and is completely bent back or if there is something Im missing. Strange thing is the test reports inidicate no issues. My newbieness is shining bright here but I really could use some advice. Do I attempt to bend the leaf back or replace the switch? And, what caused it to do this?


#2 9 years ago

The switch is probably still good but not triggering the button.
Try bending it back a little and go easy with it.

#3 9 years ago

Thanks Mike, I was kinda hoping you would reply. I actually started to adjust it then stopped, took picture and posted for advice. I did hear the pronounced "click" when I looked at it earlier. I have an adjuster and I will go easy as I have a way of mangling them.

#4 9 years ago

Mine had the exact same problem.

That should fix it. Yours is also a LOT cleaner than mine was when I got started.

#5 9 years ago
Quoted from Johnny:

Mine had the exact same problem.

Mine too.Bending it carefully as others have said should fix it

#6 9 years ago

Well, I actually took the switch off and looked at it and only then did I realize how the drop target worked. The leaf looks normal, it doesnt look bent so Im still a little puzzled. I reinstalled the switch and when I manually engage the drop target it comes to almost 1/16" of making it click. Could the spring just not have enough tension or is it really just bent and I dont see it. Sorry to keep asking but I hesitate bending the leaf that looks normal. Thanks. I appreciate the help from everyone.

#7 9 years ago

From the pics the spring looks fine.Switches sometimes do tend to open up
wider from going thru so many cycles and will not look bent.I recently had
a switch problem on my LOTR and the switch was fairly new and wasnt bent
at all i just bent it down a little bit to make contact with the button and
problem solved.

#8 9 years ago

I believe that the phillips screw on the end is an adjustment .Try and see if it makes contact.

#9 9 years ago

I tried adjusting with no luck and then went back to the basics... F103 fuse was bad. Sad thing is the replacement burned up instantly and I cannot locate anything that would be causing this. No final frontier tonite, as if . Im not going to get stressed over it anyway. Sometimes its best to step back from it for awhile.

#10 9 years ago
Quoted from Silverballer:

Sometimes its best to step back from it for awhile.

Good advice! maybe you will have a brain storm later and figure it out.

#11 9 years ago

Heres some more info is the coil locked on when you powerup your game?
this probably why the fuse is blowing and could be from a locked on coil sm1-26-600
or the other coil in your pics the one with the green wrapper starting with AE-
or faulty transistor Q13 on the 8 driver board.

Games with Solenoid Numbers Above 28 (Auxiliary Driver Board).
Even though the WPC driver board only supports solenoids 1 to 28, there can be solenoids numbered up to 44. Most often seen are numbers 29 to 36, which use transistors in the fliptronics section of the board. If the game only has two flippers, the fliptronics section will have two flipper power (TIP36) and two flipper hold (TIP102) transistors that may be used by the game for things other than flippers. Also several games (Indiana Jones, Twilight Zone, Demo Man, Roadshow and Star Trek Next Gen) used an 8-driver auxiliary driver board, which contained eight more TIP102 transistors for even more flash lamps or coils. Note this board also contains circuitry for an extra ninth switch matrix column (used on STNG, Twilight, Indy Jones only).

This auxiliary driver board could be problematic, especially on Star Trek Next Gen. On Star Trek, this board needs +50 volts for a "tieback diode" voltage for the circuit (because it controls solenoids, and not just flashlamps; all the other games that use this Auxiliary driver board only control flashlamps). The 50 volt tieback power is connected by a thin violet/yellow wire which connects to the playfield's single drop target coil (at the back of the playfield), and goes to the Auxilary Driver Board. If this wire breaks, or if some other power wire in this coil power daisy chain breaks, it can cause the two under-playfield diverter coils to lock on (after they're first activated in game play!) If the problem is not found quickly, the diverter coils and their driving transistors can fail. Transistors on the auxiliary driver board will short out in a couple of activations on Star Trek if the tieback voltage is not present on the board. If the two Star Trek diverter coils lock on after a game is started, check the violet/yellow wire which connects to the playfield's single drop target coil. Additionally, add 1N4004 diodes to the two diverter coils (banded side of the diode to the coil's power lug), and test the TIP102 transistors on the Auxiliary driver board.

If a transistor shorts on the Auxiliary driver board, this will cause the driving coil to lock-on as soon as the game is turned on. Again on STNG this is very common for the under-playfield diverter coils. With the game off, check the diverter coils first - they should have 7 to 9 ohms of resistance (tested in-circuit, any less and replace the coil). This transistor is Q13 on the 8 driver board runs the sm1-26-600 coil.Don't bother testing the transistor(s) on the Auxiliary driver board. They will *not* test correctly in-circuit. Just replace the TIP102 and it's companion 2N4403. Replace *both* transistors at the same time! Do not skimp here, or you will have to replace both transistors again after the game is turned on! Also test all the resistors related to these two transistors, and the 1N4004 diode (the diode and resistors can be tested in-circuit). Buzz out all traces related to the two transistors also, especially the 50 volt tie-back trace.

Driver Transistor Operation.
As described above, the main driver transistor (a TIP102 or TIP36) completes the coil or flash lamp's power path the ground, energizing it. But there are other components involved too!

Each driver transistor has a "pre-driver" transistor. In the case of a TIP102 (the most common WPC driver transistor), this is a smaller 2N5401/MPSD52 or 2N4403 transistor.

If the main driver transistor is a TIP36c, this is pre-driven by both a TIP102 and a smaller 2N5401/MPSD52 or 2N4403 transistor. The bigger TIP36c transistor is an even more robust than the TIP102, and controls very high powered, high use coils (like the flippers).

Then before even the smaller 2N5401/MPSD52 or 2N4403 pre-driver transistor, there is a TTL (Transistor to Transistor Logic) 74LS374 chip. This is really the first link in the chain. This is what in affect turns on the smaller 2N5401/MPSD52 or 2N4403 pre-driver transistor, which then turns on the TIP102 (which then turns on the TIP36c, if used for the coil/flash lamp in question), and energized the device.

This series of smaller to bigger transistors is done to isolate the hi-powered coil voltage (50 volts), from the low-power logic (5 volts) on the driver board. Also the 74LS374 chip (operating at +5 volts), which really controls the transistors, can not directly drive a high power TIP102 or TIP36c transistor (which is controlling 50 volts).

If ANY of these components in the chain have failed, a coil/flashlamp can be stuck on, and will energize as soon as the game is powered on!

I have a Stuck-on Coil (or Flashlamp), What should I Replace?
A short summary (before reading all the info below). The following procedures will test the driver and pre-driver transistors in question. If either is bad, it will need to be replaced. When replacing either a driver or pre-driver transistor, replace them both (or in the case of a TIP36, replace the TIP102 and smaller 2N5401/MPSD52 or 2N4403 transistor)! A shorted transistor will cause the other transistors in the link to be stressed, and they should all be replaced.

Inside the front cover of the game manual is a list of each coil used in the game. Also listed are the driving transistor(s) for each coil. Use this chart to determine which transistors could potentially be bad. Also use the schematics.

If after replacing the driver transistors the coil/flashlamp is still locked on, then replace the TTL 74LS374 logic chip. The TTL 74LS374 can also go bad (though it is not real common). This can be tested with the diode function of a DMM (red lead on ground, black lead on each leg of the chip) A value of .4 to .6 should be seen for all pins except ground and power.

Also if the new TIP102 transistor is not soldered in correctly, this can cause the TIP102 to short again. This happens becasuse the old TIP is hastly removed, destroying the plated-through holes in the circuit board. After soldering the new transistor, make sure all three transistor legs are connected to their traces. Use the continuity feature of a DMM to test this. Particularly if the center leg does not connect to the 1n4004 diode (trace on the component side of the board), the TIP102 will work for one "fire" and then lock-on during game play and destroy itself.

Also remember to test the resistance of a coil after replacing the driver transistors. If a coil gets hot, it can burn the painted enamel insulation off the coil windings. This lowers the overall resistance of the coil because adjacent windings short together. If resistance gets much below 3 ohms, the coil becomes a "short", and will fry its associated driver transistors very quickly!

1 year later
#12 8 years ago

I know its an old post but jeez mike your explanation is gold dust for a newbie to get an idea of how these machines work. Thanks.

1 year later
#13 7 years ago

The tie back mod is made on the Drop down target yellow coil or green coil?

#14 7 years ago

Either, makes no difference.....
The two coils on the drop target and the two diverter-coils on the spiderramp are all 4 connected (daisy-chained) by the violet-green 50v wiring.
The most common used is the 50v lug from the green coil on drop-target.

#15 7 years ago

I'm dealing with this issue now as well, but my upper divertor coil works, but not the lower (lower as per the coil description, when the PF is up, its actually the upper one of the two). Everything seems to check out on both boards.

#16 7 years ago

It's not always the daisy-chain effect, sometimes just one coil went bad or has a broken wire.

First look at the common things which can go wrong with coils

#17 7 years ago

I don't see a diode on that coil. Is it on the opposite side in that picture?

#18 7 years ago

Oh wow, this is one of the earliest threads I ever started on Pinside. STTNG was very intimidating to work on in my early days. Its still a basta but I am no longer hesitant to dive right into it. This is by no means any indication that my repair skills have improved. Still, back then I had to call in the local awesome Pinsider ace for this one- thanks Stangbat!!! If I recall correctly the issue was a bad Q16 and the pre-driver transistor at Q8, as well as a toasty coil. This was couple of years ago and the machine still flying warp 9.9. Superpin. I love STTNG. Not quite as much as lamp but I do love it.

#19 7 years ago

Can someone tell me what wires are on each of the drop target coils, as in the lower and upper lug for the coil that kicks the target up, and the front (closer to the coin door) and back lug (closer to the PF) of the smaller coil that drops it?

Someone seriously messed with mine, the yellow wire was not connected and wrapped around something else tied off, yet the upper diverter still worked...?!

#20 7 years ago

bump, please help.

#21 7 years ago

For the larger coil that kicks the target up- lower lug is 2 purple and greens and the upper lug is orange w/white stripe.
For the smaller coil-the back lug is the yellow and the front lug is 2 purple and greens and a smaller purple.
Hope this helps and sorry to make you wait.

#22 7 years ago

STTNG Drop target coils 001.jpg

#23 7 years ago

Awesome man, exactly what I needed!

One more question I forgot, do you have diodes on the diverter coils, and if so, did you add them as per clay's description in the post by pinmike?

Looks like someone really messed mine up, my aux driver board has been hacked so bad due to the tieback wire not being connected anywhere.

The board has all the pre-driver transistors removed, and two of the holes for these are jumpered on each, again with no tieback. Somehow, the only issues is the lower diverter not working, as the coil has been locked on and melted, but the upper one does. Given all this, I'm surprised they are both not working (or better yet completely melted, or locked on), so apparently someone has hacked their way past the tieback voltage, but I don't understand how it works as is.

I don't know if I should hook it up correctly and give it a go, or order another board (only $50) and try from there. I'm leaning towards the latter. This board is so far gone from repair I'm not even going to try.

#24 7 years ago

Clay is the man when it comes to anything pinball and Mike's review was excellent. Still, I do not have the diodes on the diverter coils and I have not encountered any issues. I bought a new board but it turned out my original was repairable and I re-installed it and kept the new one as a backup.

#25 7 years ago

The diodes are just to bulletproof that daisy-chain.
Originaly it's taken care of on the boards.

2 months later
#26 7 years ago

So I'm finally getting around to working on this today. I got a replacement driver 8 board from arikisum for a RS that is near perfect and unhacked. Checked all the transistors, and this board looks solid. I have to change the jumpers for STTNG from RS. I read a few threads on RGP about this where people noted they were the same for all games using the driver 8, but this is not the case for anyone attempting this down the road. The boards have different jumpers, and the parts list for the boards in each manual list different 0ohm resisters (jumpers) at different locations for each game.

Anyway, this crappy tieback wire got me thinking. I looked at another machine where the tieback was not on the daisy chained purple lug for the drop target drop coil, but the actual drop target reset coil, also right there. Obviously, this shouldn't matter, since they are both tied into the same daisy chained line.

Given the issue with the possible breaking of the tieback, and the immense amount of issues that can follow, why not further attempt to avoid this by splitting the tieback to both of these coils? I'm going to cut into the wire, and split the tieback so it then goes to the drop target reset and drop target drop coil, thus if vibration ever breaks one off in the future or whatever, you have a back up connection for the tieback, and the driver 8 isn't bent over. I still think this takes some acknowledgement that you need to still quickly take a look at both o these connections when you're under the hood each time, just in case.

Good idea?

#27 7 years ago

Doing this won't hurt anything, but it won't help either. All of the purple/green wires are already connected. The larger issue with the "tie back" circuit is the crappy IDC connection for that purple/green wire at the 8-Driver board. I'd repin that connection with a Tri-Furcon crimp style pin.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The new place for pinball repair info

#28 7 years ago
Quoted from ChrisHibler:

Doing this won't hurt anything, but it won't help either. All of the purple/green wires are already connected. The larger issue with the "tie back" circuit is the crappy IDC connection for that purple/green wire at the 8-Driver board. I'd repin that connection with a Tri-Furcon crimp style pin.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The new place for pinball repair info

I actually just re-read clay's notes, and he stated to do the same, connect the tieback to two coils rather than one for the same reason. He also noted the differences in the driver 8 board jumpers, funny, I don't recall reading either of those points before today.

That's a good idea about the IDC connector though as well, I will do that.

Turns out when I got everything working with the machine (over 5 hours now blah) the small coils to bring the drop target down is shorted, but the board now works and my under PF diverters work.

#29 7 years ago

I should add the jumper configuration for different games to the Wiki.

Connecting the tie-back to two coil lugs doesn't help unless you split the wire prior to connecting to the two coil lugs. I assume Clay suggests this to add a redundant connection should the wire break free. But, simply "daisy chaining" the wire doesn't help.

That little -600 coil burns up easily...
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#30 7 years ago

That's what I had mentioned previously, splitting the tieback, I guess with a molex connector, with one end being crimped with two wires to two separate lugs in the same chain, ie the two coils in noted. Then if one breaks off, you have a second still connected.

Quoted from ChrisHibler:

That little -600 coil burns up easily...

And because I was stupid and didn't check the coil before putting back in the new driver 8 (assuming like a total ass that the board was the only issue), I took out the tip102 as well. I swapped that out, and have to order the coil today, but disconnected it for now, and the machine is now up and playing for the first time, just no auto down on the drop.

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