(Topic ID: 116159)

Tips for replacing a transistor on a SAM driver board

By DnDPins

4 years ago

Topic Stats

  • 19 posts
  • 10 Pinsiders participating
  • Latest reply 4 years ago by Atomicboy
  • Topic is favorited by 4 Pinsiders


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#1 4 years ago

I have a LOTR LE (uses the SAM board as Whitestar was not available) with a failed pop bumper which does not fire in test mode. I checked the ohms on the coil and it seems good so probably a bad transistor. 2 questions:
1) Testing - Chas from Stern support suggested shorting the transistor to ground to determine that the transistor is the problem. Do you guys test this way? What is the safest way to test this? What about measuring in circuit?
2) This will be my first component replacement on a board. It seems pretty easy since it is a through component. Any things to be particularly careful for?


#2 4 years ago

Bump hoping for some help.

#7 4 years ago

Thanks for the replies guys. I am OK with my soldering skills and I know that working on a board requires another level of skill. I will be ordering a temperature controlled soldering station and a magnifier and set up a desk for board work and have old Bally boards to practice with.

My first experience working on a board was the Wheel board on my WoF. It needed a new surface mount transistor...now that was a real pain. My biggest problem was that I removed the pad while desoldering. I was able to buy a new board and at least I have the original as a spare.

Hopefully, my issue will not require a new transistor. I will try the things mentioned above and post tonight.

Thanks again guys,

#10 4 years ago
Quoted from Taxman:

What's wrong with shorting a Tx to ground?

It seemed safe enough to me...admittedly, my knowledge of electronics needs to be improved and I am always looking to learn new ways of troubleshooting and fixing my machines. Really I was really looking to see if that is a test that many others do as well. I have spoke to Chas and Pat many times and have always gotten excellent support, I was just looking for a little extra comfort before doing it.

In order to perform the grounding test, with the machine on and the coin door is closed I:
1) Clip a wire to the ground strap
2) Touch the other end of the same wire to the top tab of the appropriate transistor for a split second

Thanks to Taxman and inhomearcades for you feedback on this!


#18 4 years ago

Atomicboy is the winner! Each coil measured 10.3 ohms and all wires looked fine. With the playfield up I went into test mode and jiggled the small wire and the pop fired. I did notice there was arching on this pop only and after I jiggled a little more, the small wire broke off. This will be an easy fix within my current skill set.

Thanks everyone!

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