(Topic ID: 254552)

Space Invaders - Solenoid Problem


By nibre

9 months ago



Topic Stats

  • 10 posts
  • 4 Pinsiders participating
  • Latest reply 9 months ago by slochar
  • Topic is favorited by 1 Pinsider

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#1 9 months ago

I have been working on a Space Invaders for a while.

1.
At first none of the solenoids worked (everything else seemed to work). I did a lot of testing and cleaned the molex connectors but nothing seemed to work. The fuses were ok. Suddenly, when I measured the voltage on one of the solenoid board test points (TP5 or TP3) the solenids came alive! How can this be explained?

2.
The right thumper bumper solenoid still doesn't work. I have measured all three bumper solenoids and they are about 12 ohms each. The right bumper moves as it should and the score/sound is activated when the bumper is hit by the ball (so, there is nothing wrong with the switch). Any suggestions what might be wrong here?

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#2 9 months ago

Just a couple things to check...
Have you verified that the driver board transistor for that coil is not dead?
I'm assuming you have 43v at the coil as it is daisy chained from that coil on, so another coil would not be working, but worth asking.
When you said you cleaned the molex connectors, did you just clean the headers? They might work but if the pins on the connector are bad, it would still possibly not work. Wires can break off or the pins can be broken in the connector and make no contact.
Check the Diode on the coil as well, doubt it would cause it to completely not work, but if that failed it could have caused something else (like the transistor) to fail.
You can check http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Solenoid_Driver_Board_Issues on pinwiki as well for some ideas.

#3 9 months ago

The transistor controlling the right thumper bumper is Q10 (SE9302/TIP102), right?

Do I have to desolder it to measure it? Because of the three legs, I find transistors difficult to desolder (even if I use a solder sucker).

#4 9 months ago

Yes, it does appear to be Q10 which is a TIP102.
Check the link I posted above to Pinwiki and it tells you exactly how to test the transistor in circuit, so no desoldering. Just need a DMM and to turn the power off.

#5 9 months ago

You can momentarrily override the coil transistor by shorting the ground of the game to the transistor's metal tab. If the coil fires it's a board problem if not it's a problem with the coil or it's wiring.

There is a jumper on J3 of the the SD board that moves 5v from the power supply to the coil section. Often that jumper or the solder to the pins gets loose or cold. That causes all your coils to die but they come to life with a light touch or wiggle.

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#6 9 months ago
Quoted from BigAl56:

There is a jumper on J3 of the the SD board that moves 5v from the power supply to the coil section. Often that jumper or the solder to the pins gets loose or cold. That causes all your coils to die but they come to life with a light touch or wiggle.[quoted image]

Al since you worked there at the time... why did they design the circuit this way? It's caused a lot of grief over the years so much so that most people I know tie the 2 points together permanently. Was it designed in modules by separate people and they kind of melded it together at build time?

#7 9 months ago

Nothing wrong with the transistor, the coil or the jumper. But when I removed the solenoid board (to check the J3 jumper) I found that the solder point on J5 (connected to Q10) had cracked. I resoldered it and now the right bumper works as it should!

Thank You everybody for the input. I learned a lot!

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#8 9 months ago

Glad you got it figured out!
Those cold solder joints can be an issue like that.
Might be worth checking the other boards just to make sure you don't have any more.

#9 9 months ago
Quoted from slochar:

Al since you worked there at the time... why did they design the circuit this way? It's caused a lot of grief over the years so much so that most people I know tie the 2 points together permanently. Was it designed in modules by separate people and they kind of melded it together at build time?

Good question. That's a bit of early 1970s electrical EE trivia. It was industry practice at the time - following UL and MIL rules. Our head engineers were former USAF and Zenith radio engineers in the R&D group. They followed military specs. The spec required a power supply donor circuit to be separated from from the recipient circuit. The jumper was a sneaky but allowable way around that restriction. Otherwise the PS would have to have been a separate board from the solenoid driver which is how all the other manufacturers did it.
This is why Bally games of that era do not have a separate power supply. One less board.

#10 9 months ago

Clever, same board but completely separated.
Less modules to carry spares for/fix.

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