(Topic ID: 238627)

Bally Star Trek Target only scores occasionally


By Pinslot

4 months ago



Topic Stats

  • 8 posts
  • 4 Pinsiders participating
  • Latest reply 4 months ago by spfxted
  • Topic is favorited by 1 Pinsider

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StarTrek_SwitchMatrix_Capacitors.jpg
switch_with_missing_component (resized).jpg

#1 4 months ago

Hi,

I'm going thru a Bally Star Trek I just bought.

This is driving me nuts. The middle of the 3 targets, the L in the L - L - Y targets on the lower right side of the playfield only activates occasionally. I have adjusted the switch and have plenty of experience in doing this. The other two work perfectly and always score when hit. The middle one only scores when a fairly slow shot hits it. Fast shots and moderately fast shots don't work at all.

I compared it with the outer two targets and noticed that a round ceramic capacitor* is missing. (See photo). Could this be the reason why the switch is so reluctant to work?

Looking forward to hearing from you guys.

Stefan

switch_with_missing_component (resized).jpg
#2 4 months ago
Quoted from Pinslot:

I compared it with the outer two targets and noticed that a round ceramic capacitor* is missing. (See photo). Could this be the reason why the switch is so reluctant to work?

Yes the missing capacitor is absolutely the likely cause of the problem of missed fast hits of the target switch.

These capacitors often fail by going short circuit and cause other problems in the switch matrix. Operators simply cut them out to get the games back up and running but fast hits will sometimes be missed.

Install a 0.047uF 50V capacitor.

The purpose of the capacitor is to extend the amount of time that switches appear as closed between MPU board scans of the switch matrix to avoid very fast switch closure/releases from being missed.
The capacitors are only installed on switches that can activate and release at very high speed such as target switches, pop bumper switches and some rollover switches where the ball can travel very fast over them.

The switch matrix schematic in the manual shows which switches should have capacitors installed.

StarTrek_SwitchMatrix_Capacitors.jpg

#3 4 months ago

Thanks for this very useful reply.

#4 4 months ago

One more question: do they have to be soldered a certain way round, like diodes?

#5 4 months ago
Quoted from Pinslot:

One more question: do they have to be soldered a certain way round, like diodes?

There's no wrong leg to solder. No polarity.
faz

#6 4 months ago

Thx

#7 4 months ago

Today I soldered a capacitor between the switch contacts. It makes a huge difference. Thanks a million for the help provided.

#8 4 months ago

Bingo Bango! Where no problem has gone before!

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