(Topic ID: 235347)

Gottlieb Sys3 Blows MOSFET and Capacitor

By Kyrosfear

11 months ago

Topic Stats

  • 18 posts
  • 4 Pinsiders participating
  • Latest reply 10 months ago by crlush
  • Topic is favorited by 2 Pinsiders


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#1 11 months ago

Hey guys. I am having a tough time tracking down this issue and I would appreciate any help.

Backstory: I picked up a Frank Thomas' Big Hurt that had a litany of problems. I have fixed everything except for one final issue which is a nonworking left slingshot. The original manual came with the game and someone had underlined the left slingshot (Sol. 2) on the solenoid page, so someone else at least knew it was not working.

Repair: F17 was blown below the playfield (the fuse for that solenoid). Q3, the associated IRL530 MOSFET on the solenoid driver board (SDB), was also blown. I checked the solenoid and it was fried too. At this point, I figured the bad solenoid had taken out the fuse and transistor. After replacing the bad solenoid, I removed the SDB to replace the MOSFET and upon doing so, found that whoever replaced this transistor last (I assume the same guy who underlined it in the manual) had bridged the source (S) leg of the transistor to the capacitor directly beside it (C14). That cap (.01uf 50v) also tested bad, but the R64 resistor (2.2k) was still good. After replacing the faulty parts and hooking everything back up, I went into test to activate the solenoid. The moment I did so, F17 blew. The new IRL540 MOSFET and C14 blew again too.

At this point, I thought that the solder short had damaged something else on the SDB. I have a spare SDB that I use for testing so I put that in Big Hurt. All of the same parts (F17, C14, and Q3) blow when the solenoid is activated, so I know the issue is not the original SDB. I traced the wiring to and from the solenoid and I could not find any shorts.

I am looking for some suggestions as to where to check next.
Thanks in advance.

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#2 11 months ago

If its not already done, you might shunt all ground white wires on top left of the tranformator as it is preconised on pinrepair.com

Here :

#3 11 months ago

Thanks for the suggestion, and the ground mods still need to be done to this machine, but I am not sure how floating grounds would cause these parts to blow. Am I missing something?

#4 11 months ago

I'm pretty sure the problem came from that cause I've never have any Mosfet burns after I did the ground upgrade.
You might done this first before check anything

#5 11 months ago

As you can see on schematic there are 2 transistors legs shunt together and link to the capa directly...also every components (capa, transistor and resistance )are the same on every solenoid lines so follow and check a working line (values between every transistor legs in both way +- & -+ on multimeter and compare it to the non-working sol. line...you might have same values everywhere and also test every lines of sol. 3
If you change transistor be sure that you got an IRL and not an IRF.
When IRL burn it also burn A3 board that's why there are shunts on the back (bought my stargate with and add some after many irl burns... I shunt all ground wires and now works pretty well since 8 month...another one burned but it was because a motor broke without protection between it and A3 so I add a fuse after replace the motor...all works now...for how long)

Quote: pictures cames from www.pinrepair.com

And take your time by checking the most you can.
Have fun

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#6 11 months ago

There is a way easier method of tieing the grounds together.
See: http://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Ground_Improvements_for_System_80B_at_the_Transformer_Panel_-_.22Tag_Team_Pinball.22_to_.22Spring_Break.22

The article is from the PinWiki 80B section but applies to System 3 also.

Like WhiteStar driver boards that use FETs, there are tiny connections that must be in place for the part to operate correctly. When not in place, one side effect is for the FET to switch on once and stay locked on.

Post pics of the front/back of the board. Let's have a look.
Chris Hibler - CARGPB #31
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#7 11 months ago

Okay, here is an update:
I did the ground mod (tying all grounds directly into the transformer plate) and the issue persists.
When the coil for the left sling is disconnected from the harness, everything is fine. Once the coil is hooked up, as long as I do not activate it, everything is fine. As soon as I activate the coil, the MOSFET (Q3), capacitor (C14), fuse (F17), and the diode on the coil all blow. I have tried a different solenoid driver board and this is a new coil that has good resistance (10ohms).

Am I correct in thinking that there has to be a short somewhere?
Thanks again for the help.

#8 11 months ago

So check if there is no shunt between + and ground, unsold coil and put your MM on Ohmmeter then touch wires...nothing might happens on Ohmmeter.. if it ring or show a value between 0,1 to 1 it's bad

#9 11 months ago

I think you already unsold coil and test wires ohm value...

Also did you disconnect mechanical parts of these sol2. coil?

And follow all common wires links to sol2 under your playfield to find a potential unsold wire...

1 week later
#10 11 months ago

I just pulled the new coil, and it tests fine. I also tested the two wires feeding the coil, and they are not shorted.

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#11 11 months ago

Here is my logic, keeping in mind that all of these parts are blowing only when the solenoid (Sol. 2) is activated:

The signal (i.e., voltage) to fire the solenoid comes from the driver board through the MOSFET and goes to connector A3J5 (pin 3). It leaves the board connector along a white/red wire that travels through the harness connecting to the positive tab on the coil. The signal then goes from the coil’s ground tab along an orange/black wire to the fuse holder, and all of the solenoid fuses are daisy-chained together (pic below).

I ran a solenoid test and all relays and solenoids except for Sol. 2 are working. As I mentioned above, I have two solenoid driver boards and this is happening on both of them. Doesn’t that mean that there has to be a short somewhere between connector A3J5 and the fuses? If the short was before A3J5, then it would be specific to the driver board. If it was after the fuses, it would blow them all, correct?

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#12 11 months ago

Not sure...fuses are here to protect transistor board so I think if there's a short after fuse, only fuse will burn also when there's no coil soldered.
But test if there is a short between orange black and +48VDC top fuses sold together but probably nothing...the problem is probably that the signal black orange is cut somewhere (but I don't think so because Q3 might not blow) OR the ground on Q3 is cut somewhere
Also test the red mark I made on schematic, put your test pin voltmeter directly on the board near Q3 and the other pin to A3P7 ground connector on A3 and also follow those ground wires to the top

Good luck
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#13 11 months ago

This one is definitely giving me a fight, but I appreciate your help Benhurr.

The MOSFET has good ground all the way to A3P7. I also tested the ground wires from connector A3J7 to the ground tie-in at the bottom of the cabinet and they are good. I cut all of the zip ties holding the white/red to the harness and followed it all the way from the coil to the SDB and there are no visible issues (e.g., shorts). I am stumped.

#14 11 months ago

Did you check volts coming to coil wires without sold the coil on them?

2 weeks later
#15 10 months ago
Quoted from Benhurr:

Did you check volts coming to coil wires without sold the coil on them?

I disconnected the coil, then put the probes of my multimeter on the coil wires of the harness. When I activated the coil (Sol. 2) in test, the voltage momentarily spiked (as it should have). Nothing blew.

#16 10 months ago

Is the diode good on coil? And is the power hooked to the banded side of diode on coil? If everything works fine when coil is disconnected then either coil or diode is bad, or power is hooked to wrong side of diode and is sending power when coil is energized back to board.

#17 10 months ago
Quoted from Benhurr:

Did you check volts coming to coil wires without sold the coil on them?

Quoted from crlush:

Is the diode good on coil? And is the power hooked to the banded side of diode on coil? If everything works fine when coil is disconnected then either coil or diode is bad, or power is hooked to wrong side of diode and is sending power when coil is energized back to board.

Well gentlemen, you nailed it. The power wire was going to the wrong side of the coil. It all makes sense now:

The coil went bad and whoever tried to repair it soldered the wires on the wrong leads. Afterwards, they could not figure out what was wrong, and that is how I got the game. As I was trying to repair it, I never thought to check the wiring soldered to the coil. This is another one chalked up to "check the simple things".
Thank you guys for your help.

#18 10 months ago

I had a wire come off a coil and short on the other side, after finding the wire off it looked like thats where it went so I soldered it there then blew all kinds of stuff, took the board to a pro and the first thing he told me was to make sure all power hooks to the banded side of diode, and like the moron I am I was still convinced I had it right and tried it again to mess all that I had fixed burn up again, luckily the third time was a charm and learned a good lesson.
Glad you got it working.

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