(Topic ID: 311800)

[maybe fixed] Tech: Opto issues - Stern Star Trek LE

By Zitt

5 months ago


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  • 31 posts
  • 9 Pinsiders participating
  • Latest reply 35 days ago by Schwaggs
  • Topic is favorited by 7 Pinsiders

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#1 5 months ago

Was planning on packing my STLE for travel to TPF '2022... but noticed that there was an opto issue.
Trouble shooting and eventual magic smoke ensued and now I think I have two dead opto boards 520-5239-01

I'm about 90% sure that my troubleshooting did not cause the release of magic smoke as I was quiet careful during the debug.

Looking at my Star Trek LE manual... it mentioned the opto boards' wiring on page Y39... but I can't find any schematic for the board anywhere in the manual.

Did I over look it?
Does anyone have a schematic for 520-5239-01 so that I can start troubleshooting to the component(s) which are bad?

#3 5 months ago

Page 136 of the WPT manual.

https://sternpinball.com/wp-content/uploads/2018/11/World_Poker_Tour_Manual.pdf

Or you can order one for $12 bucks from PBL. But I suspect it isn't about the money with you.

#4 5 months ago

Thanks!
I want to be able to fix the board.
Lm338s are like pennies to get in digikey.

amazon.com link »
20 qty @ 9.99 with prime shipping.
50 cents each << $11

So; hopefully I can swap the lm339 and get these boards back to functional so I can pack it for TPF.
I also ordered two from PinballLife; so it shouldn't be a problem if the part swap doesn't work.
The 2N3904s are something I have in my part box as well; so might test them with a dvm while I have it on the bench.

2 weeks later
#5 4 months ago

ok. So; my machine was unhealthy at TPF'2022.
I overnighted three more Opto boards from pinball life and installed them at the show friday morning before the show opened. No improvement.

I did send a request for help to Stern tech support via email two weeks ago... haven't heard a damn thing. and yes, I checked for spam trapped responses.

I have several issues.
1) the first one is if i connect opto board #5 to the switch matrix; it lights 5 or so optos as closed.
PXL_20220317_061146663 (resized).jpg
I've tried new opto boards; I've tried swapping with known good opto boards.

2) If I leave opto board #5 disconnected; the game functions - but it intermittently goes into warp ramp freakout mode where it awards warps indefinitely.

So; I'm left wondering what's wrong with my game.
Could there be a +5V under playfield voltage issue which causes "load" when opto board 5 is connected?
Does anyone know where +5V originates under the PF?

I checked the warp ramp optos; and even required the "entry" opto. They appear to be solid (not loose) so it's unclear to me why the enter/exit optos are rapidly triggering.

#6 4 months ago

When you say opto boards were replaced are you speaking of 520-5239-01 or the optos on the ramp?

Have you tried reflowing solder or replacing the boards with the actual optos on them that are attached to the ramp? Look for pinched or shorted wires leading from the board to the optos. Try disconnecting the optos and leaving the board connected to the switch matrix to see if the problem goes away when disconnecting one of the optos.

#7 4 months ago
Quoted from Zitt:

ok. So; my machine was unhealthy at TPF'2022.
I overnighted three more Opto boards from pinball life and installed them at the show friday morning before the show opened. No improvement.
I did send a request for help to Stern tech support via email two weeks ago... haven't heard a damn thing. and yes, I checked for spam trapped responses.
I have several issues.
1) the first one is if i connect opto board #5 to the switch matrix; it lights 5 or so optos as closed.
[quoted image]
I've tried new opto boards; I've tried swapping with known good opto boards.
2) If I leave opto board #5 disconnected; the game functions - but it intermittently goes into warp ramp freakout mode where it awards warps indefinitely.
So; I'm left wondering what's wrong with my game.
Could there be a +5V under playfield voltage issue which causes "load" when opto board 5 is connected?
Does anyone know where +5V originates under the PF?
I checked the warp ramp optos; and even required the "entry" opto. They appear to be solid (not loose) so it's unclear to me why the enter/exit optos are rapidly triggering.

Following as we have a Star Trek Premium at my dads house. Which we have swapped that opto board 3 times. Which makes it good for a while then it re-occurs later after days/weeks. Have not find a solution, havent had time to dig in it.

We have the warp ramp freakout -> leading to ship getting direct hits making it fall forward.

So if you do find a solution for your machine please do tell.

Thanks

#8 4 months ago

Nothing wrong with the optos.
Pulled the entrance opto, reflowed, and rewired with new wire and a 2pin connector

I've replaced 520-5239-01 many times

With board #5 attached, those optos show blocked regardless of the actual opto being attached or not

#9 4 months ago
Quoted from Zitt:

Nothing wrong with the optos.
Pulled the entrance opto, reflowed, and rewired with new wire and a 2pin connector
I've replaced 520-5239-01 many times
With board #5 attached, those optos show blocked regardless of the actual opto being attached or not

Forgive me for asking since I know you are a smart pinball tech but is it possible that the main connector to board 5 was repined incorrectly? Installed backwards?

That connector isn’t polarized and has 5v and ground on one end and the switch matrix on the other. Installing the connector backwards would short some of the switch matrix possibly causing the closed switches.

Just grasping at straws since none of what you are seeing makes sense.

#10 4 months ago

I'm 98% sure it's impossible to plug the main connector in backward on the opto board #5.
They have a mechanical fiction fit that prevents you from plugging it in backwards. Ok prevents is probably wrong ... I'm sure someone could do it if really committed, but in general the header on the board has features to minimize that possibility.

When i get the machine out of the PinArmor and set it up... I'll do some more testing; but you are right - nothing I'm seeing makes sense ... short of "low" +5V or some other oddball problem.

#11 4 months ago
Quoted from Zitt:

I'm 98% sure it's impossible to plug the main connector in backward on the opto board #5.
They have a mechanical fiction fit that prevents you from plugging it in backwards. Ok prevents is probably wrong ... I'm sure someone could do it if really committed, but in general the header on the board has features to minimize that possibility.
When i get the machine out of the PinArmor and set it up... I'll do some more testing; but you are right - nothing I'm seeing makes sense ... short of "low" +5V or some other oddball problem.

I think you are right. Maybe a weak 5v supply or ground connection? Maybe repin those connections?

#12 4 months ago

I emailed [email protected] on Saturday 3/19 with no response to date.
I assume this is the only email address available?

#13 4 months ago
Quoted from Zitt:

Nothing wrong with the optos.
Pulled the entrance opto, reflowed, and rewired with new wire and a 2pin connector

I’ve had the shotgun opto issue before with the 3 pros I had on route. You have an opto rx/rx issue. Reflowing and replacing the wire won’t work. Something went bad with the lense. Replace them. $4 a piece - 500-6775-01

#14 4 months ago

I also looked at maintenance logs and on one of the pros we reseated all connections on the cpu for the switch columns and that temporary fixed it on one of them.

#15 4 months ago

Zitt, so you've eliminated the boards as the issue, what else is in the circuit? If you have smoke released I would look at the opto wire bundle and see what else is it connected to. There maybe a bad diode somewhere...

#16 4 months ago

I took a look at the opto amplifier schematic and I must be missing something obvious. Where's the supply voltage for the receiver opto?

Is Stern relying on the Rx diode generating a small voltage when exposed to light?

pasted_image (resized).png
#17 4 months ago

Yes, that is correct. The receiving LED generates a very small current when lit by another LED of the same type. Stern optos have used the same design since they were sega. Struck me as super odd when I first saw it too.

https://sciencewithkids.com/Experiments/Energy-Electricity-Experiments/LED-generate-electricity-experiment.html

#18 4 months ago
Quoted from Schwaggs:

Yes, that is correct. The reviving LED generates a very small current when lit by another LED of the same type. Stern optos have used the same design since they were sega. Struck me as super odd when I first saw it too.
https://sciencewithkids.com/Experiments/Energy-Electricity-Experiments/LED-generate-electricity-experiment.html

Wow, that is going on the seriously cheap! I sort of knew you could do that, but didn't think anyone would cut corners that much! LOL

I have two of the LED boards. I'll wire one up as an Rx, and the other as a Tx and run a test. I had done a quick Rx test using a 1Meg like the Stern circuit and just using ambient lighting just after I posted. Next to fluorescent, the opto put out 0.18V, under a 'warm' LED it was about 1.5V. Granted, no clue on what wavelength makes the opto happy. So I'll try the Tx/Rx back-to-back and check that.

Just 'thinking out loud', has anyone tried a piece of film across the Rx diode as a filter (ideally the diode lens would do that)? Looking at the trip point of the comparator, it's only 100mV if the 5V supply is solid. With the pin being full of light, wonder if there's a concern of just the ambient light keeping it from tripping reliably? Or maybe raise the comparator up from the 100mV trip point w/R8 in the schematic (not shown in my SnipIt)?

Just started looking at this, so still getting my feet wet.

#19 4 months ago

I wired up Tx and Rx sensor about the right distance apart ('eyeballed it', Homer Simpson approved test jig). Rx had a 1Meg like the schematic. The Tx limiting resistor was 183 ohms.

Rx diode output was 1503mV with no ball and ambient light.
Rx diode output was 0V w/a ball blocking and ambient light.

So a decent delta V between on/off. Of course, I should really measure it in the pin, I just happened to have two of the LED boards handy. I may measure the Rx/Tx distance in the pin first and set proper and retest.

My initial guess would be to maybe adjust the comparator trip point? Zitt commented about the quality of the 5V too, that could also be the issue, or maybe it could aggravate a so-so design when combined with what the RX diode generates.

Zitt: When the board indicates the switch is closed (your problem)...is that from the Rx sensor not sensing light? Or is there always light being detected? Maybe try a piece of black heatshrink around the Rx diode to help isolate the light beam from stray light? Here's an odd guess...do you think the lighting (i.e. color, intensity) at TPF could have aggravated the Rx diode?

With a 1meg resistor on the RX line - that's a high impedance line ( i.e. an antenna) and might be picking up a transient. A clamp on EMI filter might help if so. Do any of the high currentwires run parallel w/the Rx wires? A small cap across the Rx diode connector might solve that too (keep an eye on the time constant tho, i.e. don't make it long). Or just separate the wires.

Just a bunch of WAG's, I just started to look into this a little while ago.
pasted_image (resized).pngpasted_image (resized).png

#20 4 months ago

Looking at some of my old PF pictures, just checking the connections on the power connector might be in order...given they are just pushed in place for an electrical connection. Can't see the other board under the the wires.
pasted_image (resized).png

#21 4 months ago
Quoted from mbwalker:

Zitt: When the board indicates the switch is closed (your problem)...is that from the Rx sensor not sensing light? Or is there always light being detected? Maybe try a piece of black heatshrink around the Rx diode to help isolate the light beam from stray light? Here's an odd guess...do you think the lighting (i.e. color, intensity) at TPF could have aggravated the Rx diode?

I have two problems.
the easier problem is the warp ramp flaky optos... which is demonstrated by the entrance and exit warp ramp optos rapidly flickering in test mode. I think that is likely an issue of marginal voltages from the "LED" used as sensors.
This issues has been happening on and off since I had the game new in box. Not specific to the location ... IE not ambient light. but more a function of the "whim" of the gravity of the moon in relation to the second monday of the month of june.

The second one is the stranger one. IF I hook up board $5 to the switch matrix. like 6 optos read closed (which is weird since a single opto board is only 2 optos. ) See post #5 above. I don't think it's the 5v connection as my game the leds work on board 5. IE if I unplug the sense led; the light goes off.

#22 4 months ago
Quoted from Zitt:

I have two problems.
the easier problem is the warp ramp flaky optos... which is demonstrated by the entrance and exit warp ramp optos rapidly flickering in test mode. I think that is likely an issue of marginal voltages from the "LED" used as sensors.
This issues has been happening on and off since I had the game new in box. Not specific to the location ... IE not ambient light. but more a function of the "whim" of the gravity of the moon in relation to the second monday of the month of june.
The second one is the stranger one. IF I hook up board $5 to the switch matrix. like 6 optos read closed (which is weird since a single opto board is only 2 optos. ) See post #5 above. I don't think it's the 5v connection as my game the leds work on board 5. IE if I unplug the sense led; the light goes off.

I know you mentioned you've swapped the opto boards with know good ones but one easy test is to disconnect the Rx/Tx optos on BD 5, pull the two Rx lines high and see if the 6 optos closed issue goes away. Then also ground them and see if they close If not, then focus on the matrix lines or pwr.

At least that will definitively eliminate the Rx/Tx lines doing something screwy no one has thought about.

The opto board has LED's that indicates the Rx optos status, do those seem to work and have you compared that to the DMD sw matrix test?

Closed indicates the ball blocking the beam?

#23 4 months ago
Quoted from mbwalker:

I know you mentioned you've swapped the opto boards with know good ones but one easy test is to disconnect the Rx/Tx optos on BD 5, pull the two Rx lines high and see if the 6 optos closed issue goes away.

They did not. I tried that.
I also looked at the schematics today and according to them; the +5V comes from the IO driver in the backbox.
So; it's unlikely the magic smoke I saw was from the +5V supply.

When I get the game back on legs; I'm going to measure the opto voltages for the flakey optos to see if I read anywhere near 1.5V. My gut says no. but won't know until I test it.

The other thing to try is swapping the emitter and sensor leds to make sure both light equally. Since they are the same part; it should still function properly.

#24 4 months ago

Weird thing about the LED Rx optos is they don't need 5V, it's just an opto plus a 1 meg resistor on the opto amplifier board. Still good to test tho since it all sort of starts there. I guess if the 5V had an issue, then the Tx LED could be dim, resulting in the Rx opto not producing enough voltage.

4 weeks later
#25 3 months ago

Following up qs I just got a similar issue on my at pro.
Could a dead diod somewhere on the switches cause that?

#26 3 months ago
Quoted from Nihonmasa:

Could a dead diod somewhere on the switches cause that?

Unclear which issue your asking about.

Stern is taking 25ish days to respond to my tech support emails.

The last message from them indicated that my issue with all the switches reading closed when connecting "1) the first one is if i connect opto board #5 to the switch matrix; it lights 5 or so optos as closed." is a bad transistor on the CPU board.
I haven't been able to confirm as I've asked them for a clear, legible schematic page for those switch matrix transistors.

The phantom warp ramps they last asked if I've tried swamping the "opto board" I assume they are talking about the LM339 board... but they may be talking about the board holding the opto.

These long periods of silence from them is just ... silly. At this rate my machine will be broken until 2024.

1 month later
#27 63 days ago
Quoted from Zitt:

Unclear which issue your asking about.
Stern is taking 25ish days to respond to my tech support emails.
The last message from them indicated that my issue with all the switches reading closed when connecting "1) the first one is if i connect opto board #5 to the switch matrix; it lights 5 or so optos as closed." is a bad transistor on the CPU board.
I haven't been able to confirm as I've asked them for a clear, legible schematic page for those switch matrix transistors.
The phantom warp ramps they last asked if I've tried swamping the "opto board" I assume they are talking about the LM339 board... but they may be talking about the board holding the opto.
These long periods of silence from them is just ... silly. At this rate my machine will be broken until 2024.

Any follow up from them yet?

#28 63 days ago

Yes, wondering if you figured things out.

3 weeks later
#30 36 days ago

Stern never did return my email. But there email several months ago indicated to test Q4 on the CPU board and compare it against the others. My assumption is they wanted me to test with a DVM set to diode mode. Tonight I pulled the cpu board to do that test.

The result was Q4 was identical to the others. Tested fine in diode mode. No punch thru between E and C. no opens between BE or CB.
Regardless; I had examined the poor manual schematics and had convinced myself it was either Q4 or the LVC245 on the receiving end.

I went ahead and replaced Q4 with a part I had in my parts bin. 2N3904 is a common transistor I use for a lot of my circuits. I have some thruhole parts for breadboarding. I didn't have any of the SMT ICs so this was a "shot gun" hope and prayer that just Q4 would fix it.

I tested the transistor in diode mode out of circuit; it still tests ok.

Put the CPU board back in... and The stuck switches went away. I hooked the opto boards back up... no issues.
Warp ramp works. Ship works. Drop target works.
Played a handful of games; everything just works.

So, did Q4 fix it? maybe. Not conclusive since it never tested bad. It probably needs a more in depth test that a DVM cannot provide.
Maybe the act of unplugging the switch matrix? not really sure that's it either given how "tight" the connectors are on this board. This is the first time this board has been pulled since NIB.

I do think at least one of my Opto boards went bad. It likely "damaged" Q4 in such a way that it was too slow to transition properly on the switch matrix.
I'm not ready to say this is conclusively fixed. Want to get some more games in on it when its not 108 in the garage.

#31 35 days ago

Interesting. Thanks for keeping us updated on your progress.

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