(Topic ID: 202157)

Williams System 7 driver transistors...


By MoSeS_1592

1 year ago



Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by zacaj
  • Topic is favorited by 1 Pinsider

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Linked Games

#1 1 year ago

In the manual it appears that each solenoid has TWO associated driver transistors. Is this correct or am I misreading the diagram? The target reset solenoid locked on last time I played my Black Knight, now the solenoid does not work. I'm assuming the driver transistor shorted, blew and needs to be replaced (along with possibly the solenoid), but the manual shows this solenoid as being controlled by transistor Q21 AND Q10. Why are there two? Also, it shows Q10 as being a "special" solenoid.

Lastly, do the pre-driver transistors have an ID number or are they just considered "Q21's pre-driver transistor"? And the pre-drivers for System 7 are 2N4401, correct?

#2 1 year ago

Read the manual. It says the numbers are for two different generations of board. There's only one transistor that drives that solenoid.

#3 1 year ago

Looking at the schematics, Q21's predriver is Q20. They generally follow that pattern. And it is a 2n4401 yes

#4 1 year ago

Thank you for the quick response !

#5 1 year ago

So I replaced the driver (and pre-driver) transistors for this solenoid and it still didnt work. I checked the solenoid after and realized that it is fried. The plastic housing is melted. I know I should have checked the solenoid first but I did not. That being said, is there a good chance that the dead solenoid could have destroyed the brand new transistors I just placed? I did turn the machine on and the game tried to reset the drop targets, could this have blown the transistors since the solenoid is probably shorted? I will have to wait a week or so for the new solenoid to ship.

#6 1 year ago
Quoted from MoSeS_1592:

So I replaced the driver (and pre-driver) transistors for this solenoid and it still didnt work. I checked the solenoid after and realized that it is fried. The plastic housing is melted. I know I should have checked the solenoid first but I did not. That being said, is there a good chance that the dead solenoid could have destroyed the brand new transistors I just placed? I did turn the machine on and the game tried to reset the drop targets, could this have blown the transistors since the solenoid is probably shorted? I will have to wait a week or so for the new solenoid to ship.

Depending on how shorted it is it could have. Test the transistors again with your dmm diode test, if they still read right you're probably fine

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