8mm Forum: GAF 3000s motor only turns in reverse

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Posted by Nick Quillen (Member # 5486) on September 10, 2018, 04:38 PM:

Hey everyone!

I picked up a GAF 3000s over the weekend while thrifting. Looked like it was basically unused in the original packaging, but you never know with these things. I've tested it out and it doesn't seem to work when switched to "thread" or "forward". The motor doesn't even turn on. However when switched to rewind/reverse the motor turns on and everything works as expected.

I opened up the case and found that I could manually hold the gear to the "Forward" position while the switch was in "Reverse" (thus turning the motor on) and it didn't seem like anything in the mechanics was stopping it from going forward. I'm thinking it must be something electrical, however I'm not super familiar with these sides of things. Does anyone have any ideas/guidance that might be of some help?

Thanks!

Posted by Steve Klare (Member # 12) on September 10, 2018, 07:32 PM:

I don't know this machine, but in the DC motored machines I know, each terminal of the motor goes to a switch. Each switch can select either (+) or (-) and chooses whichever one the other isn't so the motor can be run forward or backward. The switches are activated by a cam turned by the control knob.

All it takes is for one switch to have a bad contact on one side, so that in reverse you get (-) and (+) as you are supposed to, but when you go for forward you now get (+) and (nothing) and the motor won't turn.

I believe that mechanism with the movable gear you are talking about is there to choose to turn the rear spindle or the front. If you force it to choose "forward" with the motor running backwards, the rear spindle will just try to spin backwards.

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