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Title: Vacuum Variable Questions Post by: Warren on December 05, 2005, 09:42:30 PM I have a vacuum variable that has developed a short. I'm not sure how these things are put together - the collar (puller?) is loose and rotates freely. The cap seemed to work o.k. until today, I rotated the shaft to the end (max. capacity) after which the short appeared. Now as I rotate the shaft the bellows do not move (but the shaft travels in and out).
I'm guessing that the shaft came off the bellows mechanism and I'm s.o.l. with this cap. Looking for anyone with experience with vac variables to advise. TNX & 73 Warren K2ORS/WD2XGJ Title: Re: Vacuum Variable Questions Post by: WA1GFZ on December 05, 2005, 10:38:59 PM Warren,
Remove the collar and install the lead screw. Grab the screw with a rag and give it a pull. There should be good resistance when you pull the brass piston out of the body of the cap. Don't pull too far. You should see the bellows compress as you pull. Also the guts should move. Some types have 3 screws on the side of the piston through the sleeve of the bellows coming out. Either the 3 screws are out or you have a target to shoot at after you remove the spare mechanical parts. no pull resistance and you let the vacuum out. Title: Re: Vacuum Variable Questions Post by: Warren on December 05, 2005, 11:16:09 PM Warren, Thanks Frank,Remove the collar and install the lead screw. Grab the screw with a rag and give it a pull. There should be good resistance when you pull the brass piston out of the body of the cap. Don't pull too far. You should see the bellows compress as you pull. Also the guts should move. Some types have 3 screws on the side of the piston through the sleeve of the bellows coming out. I'm not sure about the lead screw - is that just the tuning shaft? The tuning shaft is has threads where it goes into the body of the cap. There is a brass disk with a couple of allen screws where the shaft meets the body of the cap - are these the screws I should be checking? Warren Title: Re: Vacuum Variable Questions Post by: Warren on December 05, 2005, 11:20:47 PM Frank,
If the screws are out would that cause the cap to short? Tnx & 73 Warren Title: Re: Vacuum Variable Questions Post by: K1JJ on December 06, 2005, 12:27:49 AM Warren,
Just in case this applies: The threaded shaft must have a locked surface to pull against. Thus, the allen screws must tighten something somewhere. Just screwing the rod w/o a solid surface to pull against will not move the vac cap inside. BTW, Frank wanted you to pull the rod out and see if there is a hard pull proving a vacuum still inside. If this is redundant info, then sue me... ;D T Title: Re: Vacuum Variable Questions Post by: WA1GFZ on December 06, 2005, 08:09:42 AM Warren, AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
If the three screws come out then the bellows may allow a short. The screws would be inside the cone. The cap in the collins 180 tuner has the 3 screws to hold the piston. |