(Topic ID: 153481)

(WPC) Star Trek: TNG - Coils not firing


By pinballholder

3 years ago



Topic Stats

  • 15 posts
  • 7 Pinsiders participating
  • Latest reply 3 years ago by Cheddar
  • Topic is favorited by 2 Pinsiders

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#1 3 years ago

Howdy, I picked up a STTNG this week and it needs a little bit of work before I can play it. This is my first dive into repairing WPC so I have been doing a lot of research on pinball ninja and asking lots of questions to my local pin heads. I have what at first sounds like an age old issue with STTNG but after digging in for a few days, appears to be something not so simple.

The two under playfield diverters and the top drop up and the top drop down coils do not fire. This of course causes the balls to be sent looping around the machine as it attempts to lock them into place before a game but can't. The rest of the coils fire fine during Solenoid testing, its just these 4 coils with the issue (yes I am looking at you Mr Aux 8 Driver Board).

So armed with the issue I went and found a slew of reasons that cause these four coils from firing. Here is what I have verified so far:
- The coils fire when the tabs on their transistors are grounded
- Fuses on main power board test out well (I even replaced F103 for good measure)
- I removed the aux driver board and verified all 8 transistors are good (one leg tested ~550 and the other at around 650, the middle around 3)
- All four of these coils look good, not fried, and they obviously fire (see first bullet point)
- The tieback wire appears connected to the correct coil (the bottom green one for the top drop)
- All four coils, when testing for volts, are testing around 71
- All four coils, when testing for resistance, are testing between 6 and 13
- All connectors on the aux driver board appear to be seated well and there is nothing burnt
- All connectors on the main driver board and the aux driver board have been re-seated

Couple of other items of note:
- Had a shorted BR1 on driver board that I replaced and that fixed a lot of issues.
- There was crispy connector for the GI in the head with bad hack in place. I re-pinned the bad pins and made new connector. GI for head is still out but I suspect myself and will revisit when the coil issue is figured out.
- The right gun motor has broken short crank arm
- I have tested most if not all the fuses by now and replaced a few
- This is a re-import that has been working fine for more then a decade, but was originally from Germany I believe

What other tests can I run to isolate where this issue is coming from?

Thanks!
Seth

#2 3 years ago

Verify that the red line on the ribbon-cable is on pin1 at CPU-J204 and pin1 at 8DRV-J1.
Does switch-matrix column9 work ? test it in testmenu T.14 and T.15 -mark & home switches.

#3 3 years ago

Check the schematics and see if the coils that are not working are consecutive. Then check the wire between the coils. Look for a break at the first non working coil and the coil upstream.

#4 3 years ago
Quoted from zaza:

Verify that the red line on the ribbon-cable is on pin1 at CPU-J204 and pin1 at 8DRV-J1.
Does switch-matrix column9 work ? test it in testmenu T.14 and T.15 -mark & home switches.

Verified and re-seated just to be safe.

I ran T.14 and it shows two closed switches. I ran T.15 and it shows one open switch and one closed switch. However, this is the gun motor with the broken short arm so switch is not engaged as expected. I manually manipulated the long arm on motor and switch registered as closed.

#5 3 years ago
Quoted from pincredible:

Check the schematics and see if the coils that are not working are consecutive. Then check the wire between the coils. Look for a break at the first non working coil and the coil upstream.

Connections between all these coils seem solid. I would think if there was a break they would not fire when I ground the transistor tabs up on the Aux Driver board.

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#6 3 years ago

Seth,

You mentioned that you tested the transistors and they all tested good. What about the pre-drive transistors? If those are bad, it could be the issue.

#7 3 years ago

This is where I show my greeness

What and where are the pre-drive transistors? I tested all 8 that were on the Aux Driver board (four are for the flashers and the four for the solenoids that are not working) but haven't tested any others.

#8 3 years ago

I can't believe you'd have a lot of board damage.

I'd try a new ribbon cable between CPU and Power Driver board.

LTG : )™

#9 3 years ago

Ok, I need to hunt down a spare cable. There is another in the machine with the same pin count, but its not long enough.

Yeah I have had the two driver boards out and they look really good, no trace damage no burn damage with the exception of the head GI pins.

#10 3 years ago
Quoted from pinballholder:

Ok, I need to hunt down a spare cable. There is another in the machine with the same pin count, but its not long enough.

I would think that Diner's cable may work

#11 3 years ago
Quoted from pinballholder:

This is where I show my greeness
What and where are the pre-drive transistors? I tested all 8 that were on the Aux Driver board (four are for the flashers and the four for the solenoids that are not working) but haven't tested any others.

The pre-drive transistors are in a horizontal row under the transistors. you should be able to use the continuity setting on your multimeter to trace what transistor they go to (I do not know off hand)

If you need more help, I can stop by this Sunday and get you all set. I fixed a similar issue on Henry Nanjo's STTNG about a year ago.

#12 3 years ago
Quoted from pinballholder:

I ran T.14 and it shows two closed switches. I ran T.15 and it shows one open switch and one closed switch.

Quoted from pinballholder:

I tested all 8 that were on the Aux Driver board (four are for the flashers and the four for the solenoids that are not working)

No, and that is why I asked to test the switches in T.14 and T.15.
Column 9 is generated at this board and it seems to work.

I circled in next picture all components in GREEN that are working since you have a working column 9.
That is 5Volt, 12Volt, Digital ground, ribbon cable correct, etc.

I circled in BLUE the connection that has not been verified, being Power-GND
so, check PowerdriverBoard J103. Is GND connected here and making continuity all the way to 8DRV-board ?
sttng_connct_8_drv_(resized).jpg

#13 3 years ago
Quoted from LTG:

I can't believe you'd have a lot of board damage.
I'd try a new ribbon cable between CPU and Power Driver board.
LTG : )™

Quoted from burningman:

I would think that Diner's cable may work

Great idea to use Diner's cable but no joy after swapping.

#14 3 years ago
Quoted from zaza:

I circled in BLUE the connection that has not been verified, being Power-GND
so, check PowerdriverBoard J103. Is GND connected here and making continuity all the way to 8DRV-board ?

Winner winner chicken dinner! Looks like the idiot (yes, me) that last removed the power driver board to replace BR1 lost track of this connector (see photo). It was tucked behind board after I re-installed the board and I never saw it. I went back and looked at my original photos I took before touching anything and it was plugged in correctly. Once I plugged it back in, these four coils started firing correctly. Looks like I just have to fix a sticky coil on the top side divertor and replace the broken arm on the right gun and I will be ready to play test.

Thanks everyone for your help! Hope this helps someone down the line.

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#15 3 years ago

good job. Someone will read this and think: Take lots off pics, review the pics after the repair. Lessons will be learned

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