(Topic ID: 10204)

Coil Stuck On. Any ideas?

By PinballGiant

9 years ago


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  • 31 posts
  • 6 Pinsiders participating
  • Latest reply 1 year ago by northvibe
  • Topic is favorited by 5 Pinsiders

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#1 9 years ago

I recently blew out a trace and transistor on the power driver board for my stern striker xtreme. I then proceeded to replace the transistor and bi-pass the burnt out trace. When I fired up the machine everything was fine, but the coil was just not firing hard enough to get the ball to fire. Upon testing the coil multiple times in succession it became stuck on. I recently bought a new coil and exact replacement transistor for the machine (thinking that the last one I had purchased wasn't quite right and thus the weak coil and eventual sticking on) but after replacing everything the coil is still stuck on. Any ideas? Thanks! Could it be the resistor?

#2 9 years ago
Quoted from PinballGiant:

then proceeded to replace the transistor and bi-pass the burnt out trace.

If you just replaced the Transistor and kept the old locked on coil in there then yes the new Transistor is most likely shorted again.You should have checked the old coil first before replacing
the Transistor.The problem could have been with the old coil.

#3 9 years ago

I think he replaced the coil and the transistor.
Which coil and transistor number did you replace?

#4 9 years ago

Yes. I replaced both at the same time. The coil is a 23-800 for a VUK and the transistor is an IRL450N.

#5 9 years ago

Check the transistor to ground with power off. Put your DMM lead on the metal tab of the transistor and the other lead on ground. Does it buzz out (show 0 ohms). If so, the transistor is bad again. If not, then the circuit that drives the transistor is turning the transistor on. There I'd suspect one of the IC chips.

#6 9 years ago

When you say "put the other lead on ground" where would that be? Thanks!

#7 9 years ago

Ground strap in the head....Or look on your board for a test point marked GND.

#8 9 years ago

okay I just checked and the transistor in questions has a resistance of .2 ohms and all the others have a resistance about 10.0 ohms...

#9 9 years ago

Yeah it's probably bad

#10 9 years ago

That seems very strange though since I just bought it and put it in. Could I have installed it wrong, did it come defective, or is it the fact that there's a ball of solder on one of the leads? Thanks.

#11 9 years ago

Can you put up some pics?

#12 9 years ago

Sure. Here's a picture of the transistor.

IMG_0364.jpg

#13 9 years ago

Go all the way down of this thread,There's more info on testing it was posted by Robertmee and Robin.It's better this way than posting the same info back and forth.

http://pinside.com/pinball/forum/topic/congo-top-gate-is-always-open

#14 9 years ago

Wait....That's a high power solenoid....Those aren't TIP transistors. They should be power Mosfets. The manual says STP20N10L replaceable by a IRL540N. You said you put in a 450N?

#15 9 years ago

In anycase, you can't really test a Mosfet in circuit like you would a TIP type transistor. Sorry, I didn't realize what transistor you were checking when you gave your earlier info.

#16 9 years ago

Try this....From Capcom's pinwiki, but same principle for the N channel Mosfet you have:

A locked on coil is often caused by a defective MOSFET driver on the driver board. With the power off, first test the resistance between pin 2 (middle) and 3 (right) of the MOSFET, disconnect the connector to the affected coil first so you only measure on the MOSFET. When the resistance is zero or close to zero the MOSFET is defective and needs to be replaced. Before powering on the machine after replacing a defective MOSFET, test the coil's resistance and check the tie back diode and it's connections because these are the main causes for a defective MOSFET. If the MOSFET seems to be good next to test is the input of the MOSFET on pin 1 (left) for a signal. When there's no pulse on pin 1 while testing the solenoid in diagnostics it could be a defective 74LS74 driving the MOSFET.

#17 9 years ago

And more info:

Repeatedly broken MOSFET driver When a defective MOSFET is replaced but fails again after a short period of use, or even the first solenoid activation, test the coil's resistance and check the tie back diode and it's connections because these are the main causes for a defective MOSFET. This also occurs when a wrong type of MOSFET is used, a non logic level MOSFET (IRF540 for example) will not be driven correctly because the gate voltage will be insufficient to fully drive the MOSFET causing it to get too hot and fail.
STP20N10L MOSFET alternative In case of a defect STP20N10L MOSFET, this part is getting scarce but it can be replaced by the IRL540N which is readily available. Do NOT use the IRF540N instead (not logic level)! Please note that these MOSFETS are quite sensitive to static electricity.

#18 9 years ago

So, I hope your 450N is just transposing and you actually have a 540N (and not a IRF version either).

#19 9 years ago

Sorry I've taken so long to answer I've been really busy. Just did what you said and in fact the mosfet in question has continuity and none of the others do. According to the guide, that means it's defective. Should I replace it again? Why would it have gone bad? Will this just happen again? Thanks!

#20 9 years ago

Make sure the coil measures correctly (ohms), the diode measures good (just replace if in doubt), and that the diode is connected in the right orientation.

#21 9 years ago

okay just put the new IRL 540N transistor in and fired up the machine and the coil is still stuck on...grrrr. Checked the transistor continuity and this time there is no continuity. Should I go further up stream? If so, where? Thanks!

#22 9 years ago

Next thing upstream is the octal D flip-flop U1.

Get a 20 pin socket while you're at it....Chip from here: http://www.greatplainselectronics.com/Category-60.asp?pg=2

#23 9 years ago

Thanks! Are these the right parts (see picture)? Is it possible that the chip could have gone bad like that? Also, is it just the chip directly above the Q4 transistor? Thanks!

prices.jpg

#24 9 years ago

If you could could you tell me all of the components I need to replace that could possibly fix the problem i just want to be done with this. Thanks!

#25 9 years ago

Yes, that's correct and it is the chip right above that bank....

The problem is Stern's whitestar documents aren't the greatest, and there was never a repair guide done on Whitestar. So, I can only tell you what I see from Stern's limited docs:

You've already checked the transistor Q4...The only things left are the two caps, the resistor and the flip-flip IC....Unless the databus from the CPU is crapped, but I would expect other issues.

And yes, if you shorted that transistor to the extent you burnt traces you most definitely could have blown U1.

Whitestar_Powerboard.jpg

#26 9 years ago

Put the new IC chip in yesterday and turned the machine on. The coil was no longer stuck on but whenever I try to test fire it nothing happens (similar to the lack of continuity issue encountered earilier). This time however there is continuity before and after the transistor. I didn't replace the 20 pin socket yet though, should I bother? Could it be the problem? Also, there was no continuity between a higher solder pad and the transitor so I added another bipass. Now, The bipass to the pin and the upstream bipass both meet on the middle leg of the transistor...is this bad? Thanks!

#27 9 years ago

Just got the 20 pin socket in the mail. Should I bother replacing it?

3 months later
#28 9 years ago
Quoted from PinballGiant:

Just got the 20 pin socket in the mail. Should I bother replacing it?

Yes is there is any discolorization on the plug.

Brought this thread back from the dead to work on my ID4. Dead flipper, has a blown trace on back of the board.

#29 9 years ago
Quoted from robertmee:

Do NOT use the IRF540N instead (not logic level)! Please

Robert, are you saying the IRF540N is not logic level and it needs to be? I am guessing the L in IRL means logic.

1 year later
#30 7 years ago

Any updates you guys? I have a low current, 20v, coil stuck on and I'm troubleshooting it now. Transistor (tip102) seems fine, but from what you guys did, it could be my U3. Talking about my LWJP.

Here is a good wiki for us whitestar owners. And this section talks about that mosfet and what is a good replacement.

http://www.pinwiki.com/wiki/index.php?title=Sega/Stern_White_Star_Repair#Solenoid_problems

6 years later
#31 1 year ago
Quoted from robertmee:

Try this....From Capcom's pinwiki, but same principle for the N channel Mosfet you have:
A locked on coil is often caused by a defective MOSFET driver on the driver board. With the power off, first test the resistance between pin 2 (middle) and 3 (right) of the MOSFET, disconnect the connector to the affected coil first so you only measure on the MOSFET. When the resistance is zero or close to zero the MOSFET is defective and needs to be replaced. Before powering on the machine after replacing a defective MOSFET, test the coil's resistance and check the tie back diode and it's connections because these are the main causes for a defective MOSFET.

"If the MOSFET seems to be good next to test is the input of the MOSFET on pin 1 (left) for a signal. When there's no pulse on pin 1 while testing the solenoid in diagnostics it could be a defective 74LS74 driving the MOSFET."

Testing pin1 of a mosfet for signal, is that done with a logic probe, or is it just the DMM but you'll see a change?

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