Triac Circuit Issues

[galgon]

So I have a skeeball machine in my basement.  For some reason the ball release solenoid is sticking closed when powered up releasing balls.  I know that the issue is coming from the main board.  Having read multiple threads on troubleshooting LE issues I assumed that the Triac went bad.  So I ordered two (doesnt hurt to have a spare) from digikey and replaced the old one tonight.  Well, that did not fix the problem. 

So now I am not sure where to look next.  Perhaps the MOC3030 chip failed?  Or one of the resistors?  I attached pics of the board and a diagram of the circuit.  I know the LED rusted off but I am doubtful that that is a problem.  Any thoughts are very appreciated.

[DonFL]

Did it just start malfunctioning?

Have you determined what is actually happening when it doesn't release? do you still have 120V at the solenoid, so it cannot release? Thought there is, is the solenoid just sticking, or being held closed/open?

Just my OCD nature, but looking at where that LED sits in the circuit, I'd be replacing it and ensuring it works, especially since that is a chunk of the circuit involved in your problem.
 
Your problem could also be further upstream, i.e., this part of the circuit is dependent on getting a proper hi/lo signal from somewhere else to effect the action of the solenoid.

[tbone321]

The first thing that you really need to do is replace that LED.  While it may not be the cause of the issue, it will tell you where to start looking.  That LED lights up when the game calls for the solenoid to release the balls.  If the LED lights up and remains lit, then the issue is in the trigger for the ball release, possibly a hung or sticking switch.  I would look for a roller or micro-switch in the ball track near the trap.

If the light goes out, then the problem is in the solenoid circuit.  I would first look at the current draw of the solenoid and confirm that F2 is still a .5A fuse and not something of a higher level.  Windings in the solenoid coil could be shorting out and while it may still work, it will begin to draw excessive current.  The previous owner may have "repaired" it by upsizing the fuse.  If the .5A fuse were to be replaced by a 5A fuse, this would allow enough current to be pulled to fry the triac.  That discoloration of the Molex connector does indicate excessive current draw. 

If the fuse is ok and the correct value, the solenoid should be ok and I would look at either the MOC3030 or the new triac.  Make sure that the one you replaced has the same pin config.  You can check for output on pin 4 of the MOC3030 but you may need to remove the triac if there is a continuous output when the LED is not lit to confirm that it is the chip and not the triac back feeding the pin.  Pin 4 should only have an output while the trigger LED is lit.

[galgon]

Thanks for the help!  I guess I should have provided a few more details.  I tested the solenoid - I took it out and put it on a working machine (Yes I have 2 skeeball machines).  The solenoid worked fine.  The machine was working perfectly a few weeks ago.  Then the solenoid started randomly firing in rapid succession.  Finally it just stuck closed (meaning power was being constantly applied). 

I pulled the logic board out (removed all connections to any inputs except power supply), powered it up and confirmed that 120v was coming from the plug for the solenoid wire.  Assuming it was the triac I replaced that.  I still got 120 volts.  I just now replaced all the LEDs on the board (they were all rusted).  I used some spares from a Dongle build.  Still 120v coming from the plug.  The LED for this circuit is not lighting up so I assume that means it is not getting a signal to close the solenoid.   

Any thoughts on where to go from here?

[vairmoose]

From the picture, the bottom two resistors look wuestionable and specially the bottom one.  Did you do a resistant and voltage check on them?

[tbone321]

The first step would be to confirm that the LED is functioning properly.  Activate the ball release and see if the LED lights up.  If so, then we know that the issue is in the 120V circuit and if not, check to make sure that the LED is not in backwards.  If the issue is in the 120V circuit, then we need to look at the two main components, the MOC3030 and the triac.  Make sure that the triac that you installed is compatible with the old one (pin layout) and if not, that needs to be replaced with the correct part first.  If all appears ok here, you can remove the opto (MOC3030) which should send the output to zero and if so, I would replace it.

[galgon]

How do you check a pin layout for a triac?  The old triac is shown in the pic below.  New triac was You are not allowed to view links. Register or Login

[DonFL]

Your triac pinout is fine, assuming you replaced it like for like, which it appears you did. I'd also strongly recommend cleaning up all the crud and corrosion on the board.

If the solenoid is staying closed, meaning its sitting with a constant 120V on it, and that is occuring no matter what you see on the 12V side (voltage present, or not), i'd be looking at the opto as your culprit. Have you confirmed you are getting the proper signaling on the 12V side? If the LED is installed properly, that will tell you, or check to see if you have 12V as shown in the schematic. 

[tbone321]

The spec sheet shows the one ordered to be the correct replacement.  There is a lot of corrosion on that board.  I would confirm the operation of the LED on the primary side and then look at the MOC3030 as a possible cause.

[galgon]

LED lights up as expected for the correct amount of time when a coin is dropped.  So this leads me toward the moc3030. 

So next steps are remove the opto and confirm that 0 volts come out?   If the opto is bad can I replace with an opto from a Linx Express (at least temporarily?  I would love to get the machine up and running for a party next week if at all possible.

[galgon]

Pulled the opto.  Powered up the board.  Still seeing 120v on the solenoid output.  Not sure where to go now. 

How do you go about cleaning up corrosion on a board?  This machine spent 20 years at the jersey shore so I understand why there is some corrosion/rust.

[tbone321]

You will probably see full voltage there if the solenoid is not plugged in.  There is a resistor and cap series circuit in parallel with the triac.  Plug the solenoid back in and see if it engages.  If so, then it is possible that either the 39 ohm resistor has shorted or the replacement triac also failed.  Remove 1 leg of the resistor and see if the solenoid continues to engage.  If so, then the triac has failed again.  Either way, I would check the value of the 39 ohm resistor and make sure that it is still within spec and if not, replace it and the cap.  I would still suggest that you measure the current draw of that solenoid.  Just because it works doesn't mean that it is undamaged.  With all of that corrosion, it would not surprise me to find shorted windings in its coil which can cause a significant current draw and lead to the failure of the triac and other components.

[DonFL]

Very doubtful a resistor is going to "short"...change value maybe, burn open (which you would see...) but if anything is "shorted" more than likely its the cap.

[DonFL]

I'm looking at the pic again, and R40 looks very suspicious..would suggest probing it a bit to see if it has actually cracked, or just pull up one lead and check its value.

[galgon]

Ok - so I tested the resistors.  Most came up Ok while testing on the board.  The 1k resistor was showing 45 ohms.  I pulled and replaced it.  However when I tested the resistor after I pulled it - it showed 1k.  Perhaps I should have pulled up one leg as suggested and tested that way.  Powering up the board - Solenoid still engaged.

Took Tbones advice and pulled one leg of the 39 ohm resistor.  Powered up and for the first time the solenoid did not engage.  So the resistor or cap was the problem.  Pulled them both and swapped with known working ones from another circuit on the board (there is a bulb flashing circuit for the upper bulb setup exactly the same way).  Powered up and Success!!!       

I tested the resistor I removed and it seems to read 39 or 40 but it jumps around quite a bit likely due the corrosion on the part.  So I suspect the Cap was likely the issue but I am not sure how to test that. 

In any case I now need to find a new 01.m z5u cap and a 39ohm resistor for the flasher circuit.  But the game can be played without it which is the most important thing.   

Thanks again for all the help.