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Stern trough opto problems


robm
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I recently purchased 2 new stern opto trough boards from a dealer – in separate transactions a few weeks apart– one a transmitter, the other the receiver.

 

After much troubleshooting, I am convinced there is a board error – or also wondering do they have very fine tolerances in the sensitivity of the LEDs? The attached is my testing – hopefully its not too complicated!

 

I have 2 machines to test in – Grand Prix and LOTR – all combinations of all boards test the same in both machines – so I know its not a wiring, machine or plug issue.

 

I have 3 sets (transmitter an d receiver) of boards

A – what I purchased from a dealer

B – out of LOTR originally (not working well)

C – out of GP – works fine in both machines

 

Part no's are

520-5173-00 transmitter

520-5174-00 reciever

 

Given that each board has 2 LEDS, the attached diagram shows where I tested each transmitter board against each receiver board, as well as checking each LED for a switch opening (ie: I did this without the board mounted so I could line up LED1 of receiver against LED2 of transmitter and vice versa.

 

The main takeaway is that receiver board C works with all transmitters, however receiver board A (new board) only works on LED 1 of transmitter board A (also new). So I suspect that transmitter board A is a problem, however I can’t work out why receiver board A does not work at all with transmitter board C (yet it works on LED1 of transmitter board A). Both LEDs are bright red on transmitter boards A and C. I am certain there are no loose connections and I reflowed solder on boards and ensured everything is correct. So this is why I wonder if different batches of leds do not work well, and wonder if the two boards I got new were from different batches? Or is there some other testing i can do?

 

Or is the only solution to get another new set - i have sent a message to the dealer, and am awaiting hhis reply, but thought i'd try the brains trust as well!

 

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@robm i had an LED opto issue with the alien head on Independence day. The optos are bright clear lens red light standard looking LEDs not I R so shining a torch into the RX should trigger a switch I also repaired a WPT that are surface mount . I purchased the LEDs from RS components and rreplaced them on board they were on. They do have a particular wave or focus spread.Hi
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@robm i had an LED opto issue with the alien head on Independence day. The optos are bright clear lens red light standard looking LEDs not I R so shining a torch into the RX should trigger a switch I also repaired a WPT that are surface mount . I purchased the LEDs from RS components and rreplaced them on board they were on. They do have a particular wave or focus spread.Hi

 

Do you recall the part number mate?

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@robm i had an LED opto issue with the alien head on Independence day. The optos are bright clear lens red light standard looking LEDs not I R so shining a torch into the RX should trigger a switch I also repaired a WPT that are surface mount . I purchased the LEDs from RS components and rreplaced them on board they were on. They do have a particular wave or focus spread.Hi

 

OK Phil - you've got me thinking. Is there a way i can modify the circuit to make either the LED trasmitter birghter, or the receiver more sensitive?

 

So the factory resistors on the transmitter board are 180 ohm - i put a 150+20 =170 ohm resistor in and it made no difference (still worked on my 'good'board C, but the 2nd LED would not work on my half working board A. Also tried a 150 ohm with same result.

Below are the schematics - any suggestions on tweaking of resistors on the reciever board if my wild idea has any merit?

 

Capture.JPG.99d855c43ab4050aac855c50a262c736.JPG

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@robm Hi Rob, OK I know the original LED is MT5000UR Ultra Bright T-1 3/4 Marktech optoelectronics it may be discontinued now but I know with the specs given you will find a replacement or NOS. Now is the type your chasing a through hole design or is it the SMD? SMD's I have. The schematic is out of Baywatch as I was repairing Independence Day but as you can see the write up and operation is exactly the same.

I also replaced the LM311N comparitor and 2N3904 I just did at the time. It was a long time ago. I did experiment at the time but the LED really needed a precise focal point to work effectively. So using resistors or trying to increase light output wont work but probably fail prematurely. It's all about narrow beam so you don't get flooding or interference from near by light output. It's a much better design than IR as you can visually see if the TX is working. Both sides use the same LEDs. Attached is the link to the MT5000UR data spec. it's safe to click.

Hope this helps mate.

 

https://www.datasheets360.com/part/d...9802010253818/

IMG_8040.thumb.JPG.938f5939b34915ab7531e2c5e3d174cf.JPG

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The LEDs are through hole but everyhting else is surface mount. I suppose i might swap LEDs 1 and 2 on the transmitter and see if the problem follows or stays. I also replaced the 2n3904 on the receiver - no difference. I just used a through hole one - looks ugly, but trying to get to the bottom of this with what i have on hand.

 

So apart from manual adjustment of angle, i assume there is nothing i can to to increase the focal point of the LEDs?

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OK - so i swapped position of LEDs on trasmitter board A (and put original 180 ohm resistor back). The problem follows the LED ie: now LED2 works, but LED1 doesn't (previously it was opposote.

 

BUT BUT BUT

 

This occurs with the 2 new boards (transmitter and receiver i purchased (i called them board set A). If i put the reciver board C (my good working orginals from another machine) in, transmitter board A works perfectly with both LEDs?????

 

So i still can't get a solution with what i have, as there seems to be an issue which transmitter you pair with which receiver

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That could be the case with the board sets as the wires will be addressed to the switch matrix however its the LEDs at a component level that it makes no difference. Same as the Bally/Williams opto TX assembly it doesn’t care one way or another if actual TX IR’s are swapped around as long as the RX it gets its light source. But replacement boards eg great lakes opto boards really want the matching pair as per switch matrix specs because of the diagnostic features.
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Well i started swapping LEDs around, as i also have a 3rd (B) set of boards that were largely not working.

 

I had the A transmitter board that only 1 LED on that would work with the B receiver. So then used the B transmitter and nothing would work there with the B receiver, but the C (fully working) transmitter would work with 1 LED of the B reciever. So i pulled that working reciver LED from the B board, put it in the LED 2 position of A board (that worked fine with C transmitter, but not A transmitter), and now both A boards work! Confused...cause i am!

 

Anyway, its working, but still doesn't make a lot of sense to me

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Confused, yes, but im glad it’s working cos I’m out of ideas too. You’re a smart cookie and know only one will illuminate in circuit but have you actually tried to test each led with a couple of volts on its legs to see if they actually illuminate? TX side is basically 12v and a resistor to the board its the RX that has more circuitry and generally where the issues exist.
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Confused, yes, but im glad it’s working cos I’m out of ideas too. You’re a smart cookie and know only one will illuminate in circuit but have you actually tried to test each led with a couple of volts on its legs to see if they actually illuminate? TX side is basically 12v and a resistor to the board its the RX that has more circuitry and generally where the issues exist.

 

That's the problem. Every led on all 3 transmitter boards lights every time. Just doesn't get recognised by every receiver board

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