(Topic ID: 235759)

GTB Count-Down Blue Target Bank transistor


By DropTarget

4 months ago



Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 4 months ago by DropTarget
  • Topic is favorited by 1 Pinsider

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#1 4 months ago

Hi All,

Does anyone know which transistor(s) control the blue drop target bank on a Gottlieb Count-Down?

Mine is locked on.
Thank You

#2 4 months ago

There's an under-playfield transistor:
pasted_image (resized).png

Looks like that in turn is controlled by Q18 on the driver board?

#3 4 months ago

Thanks, I was looking for it's driver on the driver board.

edit..

Ah, Q18 thank you

#4 4 months ago

Hmm, I changed Q18 and Q29, Q30 and the 2N3055 on the driver board. The under pf transistor tests good. The Blue's still lock on. other issues too.....like the other drop target banks not resetting.

It may be time to recheck MPU

#5 4 months ago

The playfield transistor is being driven by an open collector driver (Q18).
There really needs to be a pullup resistor on the base connection of the playfield transistor to force the playfield transistor to an off state.

I know this is a system 1 but see paragraph 5.10.3.1 of the system 80 pinwiki.
http://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Remote_Mounted_Transistors

#6 4 months ago

Thanks,

All the transistors in line check out. I'm now leaning to a bad CPU sending signal but I'll see what adding a resistor does. I Have a new CPU arriving tomorrow. Stay tuned......

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