Williams ST:TNG - issue with pass through opto switch

Machine is a Williams Star Trek: The Next Generation in Good working condition.
Besides the lamps and flasher (now complete LEDs) the whole pinball is equipped with original boards.

I have nearly from the beginning an issue with one of the pass through opto switches and cant find the root cause.
(thought I solved the problem every here and then as the game is fully playable but with Multiball 4+ it startes to miscount the balls in play)

First I thought it would be an issue of the opto switch itself and replaced it on the 7-Opto Board.
But when this did not work I also exchanged the complete 7-Opto Board, what did not solve the problem either.

Maybe it is an issue on the main board but if I shorten the switch it triggers in test menue as expected, but not with direct light.
That was also the reason why I exchanged several opto switches before the complete opto switch board (also just to be sure transmitter besides the reveiver board).

So maybe I have an issue somewhere else on the main board?
The cable all looking good as far as I can tell, identified the one belonging to that particular switch and traced upto main board.
Some dirt from all the years but no damage or loose contacts.

Any further checks and description are welcome!
If some more information or even photos could are required to be helpful just state accordingly.
But I must admit, I have a high resistance to change anything on the main boards ....

In case of mistyping or using uncommon names / description of parts I am sorry for causing confusion as I am a non-native speaker.

#2 1 year ago

???

PinRetail

Pinside+ Addict

Finding an intermittent opto can be difficult.

What I normally find when I finally locate the problem is that the actual QED123 or QSD124 Transmitter or Receiver LED is broken underneath the LED, on top of it's little circuit board. I find this when I'm desoldering, and the LED comes off the board when only one leg is desoldered.

So... broken legs to the actual LED itself is a common problem, and your pinball has a LOT of opto switches!

I would get all the balls out of the game, and then go into switch test, and slap/beat on the playfield to see if anything is triggering with vibration.

Also, while it is quite a bit of work, dirt can make an optical switch unreliable. Consider pulling every opto pair off of the ball delivery ramps under the playfield and cleaning them... and then consider it again... nobody wants to do that job! But it could just be a dirty opto.

I'm thinking about all those optos on the bottom of the ramps that are ball delivery switches, but honestly I've had more trouble with the trough optos than anything else.

For the trough opto I pull both the transmitter trough opto board and the receiver trough opto board off, and hold them in my hand, with the optos lining up. I make sure that all the LEDs are pointing toward each other, and put the game in switch test. Then I make sure each LED pair is properly activating, and I wiggle each LED to make sure that none of THOSE LEDs are sitting with one leg broken off.

Broken solder connections at the connectors to the trough opto boards are common, so re-flowing the solder at the connector is usually a good idea, unless the solder on the connectors REALLY looks perfect.

Tracing down an intermittent opto switch can take a lot of time and effort. Keep us aware of your progress!

#3 1 year ago

KEN

radium

Pinside+ Frequent

Covington, LA

10y 93,550 4,153 12 2

You said you have trouble with "one of the pass through opto switches".... do you know which one is the problem?

#4 1 year ago

???

PinRetail

Pinside+ Addict

https://pinside.com/pinball/forum/topic/how-to-determine-the-c-e-of-black-opto-receiver-leds

Ha! Good catch Radium!

Yes, if we know which switch is the problem, we can definitely help you get this fixed!

I got confused in the original description about the "Multiball+4", and thought that some random opto was miscounting the balls.

Problems with one specific opto receiver can be a broken leg to the LED, bad wiring or voltages, or...

Maybe you've just got a replacement LED that is wired wrong!

#5 1 year ago

MMG

TheMmgs

Pinside member

Yes, the faulty opto can be identified

- after power up the test report states 'check switch 62 trough release #5'
- in single switch test mode i can confirm that

And that is the point where my problem really starts.

I replaced the faulty opto after validating the led on the transmitter boards works fine.
Also the complete opto trough board is now new, as i wanted to exclude mistakes from my side during replacement of single opto.

The switch still is not working BUT if i shorten the opto it is stated as 'closed' in the single test mode.
After a while of playing the test report is showing again 'check switch 62...' as it remains in open state all time.

And that is the reason why I am a little bit confused.
What is the chance that a complete new board has a faulty opto at the exact same position?

Heap thanks for your responses so far!

I will now check for bad wiring or voltages and again start over just to ensure I did not miss what you pointed out.

#6 1 year ago

KEN

radium

Pinside+ Frequent

Covington, LA

10y 93,550 4,153 12 2

Since you have a new 7-opto board, that rules that out. I would examine the connector next. Check 3-19 in the manual to find the connector locations... 12-pin header on the opto board, J1-1 is column 6, J2-2 is row 2. But J2-2 (white-red) is what you really want to check because the other pin is the column shared by all the optos.

These go to CPU board J207-6, J209-2, but I think if you had a CPU issue there would be more switch problems than just the one opto. I wouldn't disturb any of that yet.

I am no expert so hopefully someone smarter can assist!

Screenshot_208.png

#7 1 year ago

KEN

radium

Pinside+ Frequent

Covington, LA

10y 93,550 4,153 12 2

And since I already have it open, here's the other half of the 7-opto schematic.

Screenshot_209.png

#8 1 year ago

???

PinRetail

Pinside+ Addict

Radium has mentioned the next step in testing, which you might have already done?

Put machine in switch test, disconnect the plug from the receiver trough opto board.

Use a small piece of wire or solder to connect pin 1 (green-blue) with pin 2 (white-red).

The switch test should respond to this with an activation on switch 62. This verifies that you have a good cpu switch matrix, good wires all the way to the connector.

Have you already done this?

Now, if it DOESN'T register switch 62 being closed, then you know you have a bad wire, or connection somewhere between the cpu and the trough board.

If it DOES register switch 62 (I think maybe you have already tested this?), then the problem is actually in/on the boards at the trough. (Which is what I think is going on).

So, what I do here is to reconnect the plug on the receiver trough board, and unscrew both boards (yes I know it's a pain!).

Get both boards in your hand. Make sure the game is in switch test. With the boards lined up in your hand, one by one, block the opto beam. Each should work except switch 62.

Now, move the transmitter board and align it differently, have LED 7 align with Q2, instead of Q1. Now the receiver opto (Q7) won't be aligned with anything, and Q1 won't align with anything, but the other ones will. Test them by blocking the opto beams.

Now do it the other way, have LED 2 align with Q2, and test them by blocking the opto beams.

This is hard to describe, but easier to do than you'd think. The idea is that you want to have a different transmitter LED from the transmitter board shining on each receiver LED on the receiver board.

We'll come up with a couple of things.

What I suspect is that the receiver associated with Switch 62 won't activate no matter which LED on the transmitter is shining on it. If that is the case, then yes, you have exactly the same problem with a different board. Start by replacing the receiver LED with a QSD124, making sure that the LED is properly installed with the correct leg connected to the C and E sides. (Here is the link:
https://pinside.com/pinball/forum/topic/how-to-determine-the-c-e-of-black-opto-receiver-leds ). If replacing the receiver doesn't fix it, then you are looking at the LM339 chip... I've never seen the resistors or diode be bad.

Another thing that might be the case is that the transmitter that you previously tested as OK that would be shining on the receiver for Switch 62 is now not shining on any receiver that you align it with. That would be great! Check the resistor and it's solder connections that is associated with that LED, and if necessary replace the transmitter LED with a QED123. It is extremely common for the resistors to test with no connection inside them (this is called the resistor being open), or the legs to the resistors be broken on the original transmitter trough board.

Another thing that might happen is that everything works perfectly in your hand, but doesn't work when installed. Sometimes the transmitter LED is bent a little to the side and thus not shining directly on the receiver, but this is usually bad solder connections (at the connector or the transmitter resistor).

Let us know!

#9 1 year ago

MMG

TheMmgs

Pinside member

These were great hints&tips - heap thanks for your advice and support on this topic!

Finally I now can say: everything is working

I really tested everything more than multiple times but not in structured order due to my 'assumption' from previous work.
And after replacement of some parts I did not really check the previous ones again - just because the failure was unluckily faulting the identical switch / function 62 in trough board

But encouraged by your input and following your advice just for crosscheck outlined what finally brought up the solution:
---------------------------
- clearing all balls out, machine in switch test
-> 62 not working, everything else is fine (see pic with switch test overview)
- checked and cleaned connector on opto board of receiver
-> nope, error still there / no change
- shorten trough rel 5 on trough board OR connect pin 1 (green-blue) with pin 2 (white-red)
-> it DOES register switch 62 (see pic with switch test overview)
-------
Status: wiring is ok, must be the pair transmitter receiver

So next steps, now I was looking at transmitter (tx) and receiver (rx) boards simultan.
AND I also crosschecked my old/original ones against the new boards - so if it is confusing do not hesitate to ask for clarification
-------
- disconnecting plugs from rx/tx boards and getting them unscrewed for hands on test
- first checking OLD tx if LEDs are fine (doing this with smartphone camera, see pic)
-> exactly the LED for switch 62 is not working on the OLD tx
- so checking NEW tx board
-> all LEDs are working
- checking NEW rx in line with NEW tx
-> 62 not triggering
- checking OLD rx with NEW tx
-> all fine!!!!!!!!! (see pics)
-----
Result:
-> my original/OLD rx trough board which I had repaired a lot myself in the last couple of centuries is working
-> the NEW rx and my OLD tx have defects at the same switch 62 parts

Solution:
After re-mounting and re-connecting my OLD rx and NEW tx it was a great to re-inserting the 6 balls one-by-one and see them triggering each switch while running through the ball holder

Hope the attached pics are a good help to visualize every step.
Just to point out again:
My problem was that the my old rx and tx boards had failures for the exact same switch AND after have repairing the LED and optoReceiver for switch 62 couple of times AND now replacing complete boards the NEW rx hat unluckily an faulty switch 62 optoReceiver - never thought that statistically this could happen

I am really happy (and my wife is relieved as well

radium & @PinRetail: I owe ya, mates!

Now I have to spare boards were I will replace LED and optoReveiver

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#10 1 year ago

???

PinRetail

Pinside+ Addict

NICE!

So glad you are working!

Pinball repair can be some of the hardest kind of technical work, and mostly what you need to do is just keep working at the problem when it doesn't seem like anything is making sense.

It is REALLY common to have to go back and examine every single step in your troubleshooting, one by one.

Thanks for posting that you got this problem fixed!

#11 1 year ago

MMG

TheMmgs

Pinside member

https://www.pinballlife.com/7-opto-trough-emitter-board-for-williamsbally-widebody-pinball-machines.html

I have to thank both of you for helping out and encourich me for structured error exclusion!
So posting the solution with the pics was least I could do.

This switch 62 was really driving me mad as exact that was repeating / occurring over decades - only once a direct optoRx and LEDtx failed, but I think that was due to bad solder work of my side.

That was the reason why I went for complete exchange after I found the boards, to eliminate myself from the error prone list.
And never thought of 'https://pinside.com/pinball/forum/topic/how-to-determine-the-c-e-of-black-opto-receiver-leds' so having this bad opto on the new board was after my positive test to shorten not even close in mind.

Already have seen me exchanging all the main boards and complete wiring BUT now the pinball is cleaner than ever afterwards
It was fun and I am looking forward to new rounds hitting high scores, where I never have gone before... (as the miscounting of balls always drove me nuts )

#12 1 year ago

???

pins4u

Pinside apprentice

Gaborone

3y 34,400 1,037

You are going to have continuing problems with that trough board. It was a very dumb design to put those large resistors on the transmitter board.

I would replace that board with something like this:

$32 and your problem with this is gone for good. Get rid of all the excess heat that is only going to keep frying the existing board.

1 week later

#13 1 year ago

MMG

TheMmgs

Pinside member

Ah, my dreamtime galaxy class pinball always keeps me busy - current status:

After having repaired the ball trough everything was working as designed....only the right lower flipper coil getting real hot - which weaken the shots, but that was an easy fix.

After that last repair the game play was smoothly as never before!

And suddenly all switches failed at once
Guess I will have to make up a new post as soon as I figured out what really happened

#14 1 year ago

MMG

TheMmgs

Pinside member