(Topic ID: 117875)

STTNG: Cannon/VUK issue: I need help!

By HoakyPoaky

4 years ago

Topic Stats

  • 11 posts
  • 4 Pinsiders participating
  • Latest reply 4 years ago by Matt_Rasmussen
  • No one calls this topic a favorite


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#1 4 years ago

I'll apologize in advance for my limited pinball knowledge & writing a small book here. I just want to be thorough. I've learned a lot in the last few years, but I've finally run into my first major issue with one of my pins, and my repair skills are limited & I'm not really sure sure how to proceed. I've never had an issue with this pin before, it was HUO for 10+ years & has always been taken well care of. So I read some past threads, looked over the owners manual & can't find the info I'm looking for. Any STTNG owners or Lloyd out there? Any help is greatly appreciated.

First the current problems:

I was not in the room when this issue started. I had a friend (who is not a pinhead) over who was playing my STTNG, and during his play I could hear a loud banging begin from the other room. I thought the machine was searching for a ball, so when I came in to look, both cannons were rotated to the far position & it sounded like a VUK was firing continually. When I asked what happened, my friend had no idea, said it just stopped working. No help there. The machine continued to bang away. I thought a ball might have been stuck somewhere, so I nudged the table a few times. When I did this, the Color DMD display went black. Total panic mode sets in. So I just turned the machine off.

With the Color DMD out, I had no way to view the operators menu. I checked the color DMD & all the connections looked fine. So I pulled it & replaced with the original DMD. Turned the machine on, and the old DMD was working fine. Great, now I could view the operators menu. But let's forget about the Color DMD for a moment & just focus on the main problem. The machine continued to bang away, and my original thought was that something my wrong with the LT cannon. Maybe something was wrong with the motor? So I opened the coin door to stop the banging & get into the operator's menu. At start up I got 3 errors...

1) Check Switch F8 UL Flipper But
2) LT Launcher can't find home error
3) RT Launcher can't find home error

From reading the owners manual, it says that Switch F8 isn't used, so I don't think that's the problem. When entering test mode for the cannons, I cannot get either cannon to rotate manually. The LT cannon is rotated to the far RT position, and the RT cannon is rotated to the far LT position. They won't move at all.

So I removed the balls & lifted the playfield. Upon closer inspection on the cannons, I do not see any loose wires or broken soldering points. Both wiring harnesses look like they're in great shape. I can't visually see anything wrong with the cannons.

With the playfield up, I closed the coin door & the banging started again. Now I could see where the banging was coming from. The rear LT VUK (the one that ejects the ball to the LT outer rail, not to the cannon) was firing repeatedly. In the owners manual it's the A-17049 Ball popper assembly. Upon inspection, I do not see any loose wires or broken soldering points. the connections look good. I'm not sure how the VUK even works or the parts involved with it, but I'm assuming there's an opto in there? Could it being out of alignment cause the VUK to fire repeatedly? At this point, I am stumped.

I have not tried to put the Color DMD into one of my other machines yet to see if it's working, but the CannonVUK issue started BEFORE the DMD went out, so I feel it's unrelated. I just want to get the machine working again first.

So need to get the VUK to stop firing & get the cannons to home. I want to proceed but I'm not sure where to start, but I am more than willing to learn. I always err on the side of caution when it comes to start tearing stuff apart. I have limited skills here, so trying to read the switch matrix is almost like a foreign language to me. On the plus side I do have a digital multimeter! I'm sure I can rely on you wonderful Pinsiders to guide me though this

I attached some video as well, just in case my descriptions were off. The first vid shows what happens at startup, and the second shows the VUK firing repeatedly. I've put this off for long enough & I'm ready to get my hands dirty.

Thanking you in advance for your help!

#2 4 years ago

Grab your meter and see if you lost 12 volts on the test point on the power driver board.

LTG : )™

#3 4 years ago

Where's that board located? In the backbox? Bear with me, I've never used this meter before

#4 4 years ago

Board is the biggest one in the back box. Test points are little metal studs sticking up and labeled TP and for voltage.

Youtube is littered with short how to videos for your meter and other good things.

LTG : )™

#5 4 years ago

Well I think I'm doing this right....I turned the pin on and let the VUK bang away. After about 90 seconds, without doing anything, it stopped banging. Then with the meter set to 20V DC range, I got the following readings.

TP1 (12VU) = 0.10V
TP2 (5V) = 5.0V
TP3 (12VR) = 12.05V

I'm guessing that TP1 reading is a bad sign.

#6 4 years ago

There was a thread about losing 12V after installing the color DMD.


Can you get the cannons to move in solenoid test mode? It appears both cannons are driven by 12volts from J118 on the power driver board. No clue if the cannons are related to the VUK.

#7 4 years ago

Oh, and after reading that thread, perhaps it was a fuse???

#8 4 years ago

I just took the Color DMD that I removed from the STTNG and put it in my JD. It works perfectly. The DMD is not the issue. The original DMD is installed in the STTNG & it's working fine right now as well.

Based on the reading with the meter, I think it's clear that the issue is with my 12V power supply. It's reading almost zero. Not sure how to proceed.

#9 4 years ago

Maybe it is a fuse? I'll have to look

#10 4 years ago

Ha boy do I feel dumb. Pulled the F116 fuse & tested it, it looked good visually but it was blown. Threw a new 3A fuse in there & now she's working perfectly. Turn out my first "major" fix cost less than a dollar.

Thanks for the help guys. This is exactly why I love Pinside

#11 4 years ago

It's going to do it again, and where did you get a slow blow 3A fuse for a buck?!?

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