This is topic Kelmar rewind blowing fuses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Ken Lackner (Member # 1002) on 05-09-2002, 05:32 PM:
When I was building a print today, the fuse for the motor on my Kelmar rewind bench blew. It worked fine for 5 or 10 minutes, then all of a sudden the motor quit. Someone checked the fuse, and it was blown. I replaced it, and the same thing happened about 10 minutes later. Any ideas why?------------------
This one time, at Projection Camp, I stuck a xenon bulb....
Posted by Gordon McLeod (Member # 33) on 05-09-2002, 05:49 PM:
Probably bad brush in the motor or a shorting winding on the variac
At what wpeed was it running ? THere may have been too much drag (belts,bearings clutch) for the speed and the motor of course drew too much current
Posted by Steve Kraus (Member # 476) on 05-09-2002, 08:12 PM:
If it's an old unit your motor's commutator may be shorting between segments from carbon dust. Someone familiar with motors can disassemble it and scrape the divisions clean. If the commutator is badly scored and the brushes worn it can be turned smooth and the brushes replaced but you get to a point where it is simpler just to replace the motor and be done with it.
Posted by Steve Guttag (Member # 268) on 05-09-2002, 09:01 PM:
If this is the new UL listed rewind table...replace the motor fuse with a 3 amp slo-blo...your problems will vanish. If the motor shorts or draws too much current, the fuse will blow. Prior to the big UL listing, there was no fuse on the motor. The least they could have done is to make it a Slo-Blo rather than a fast blow. Steve
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"Old projectionists never die, they just changeover!"
Posted by Ken Lackner (Member # 1002) on 05-10-2002, 01:47 PM:
This is a brand new table, only a few weeks old. The fuse that came out was 2.5 amp fast acting, so a 2.5 amp fast acting fuse went back in. 
I generally believe the manufacturers have reasons for using specific parts that they use, although this may not always be the case. Why should I use a slo-blo? thx.------------------
This one time, at Projection Camp, I stuck a xenon bulb....
Posted by Steve Guttag (Member # 268) on 05-10-2002, 02:36 PM:
Ken,I generally agree with your statement about manufacturers and fuses. Normally they are well chosen. In the case of the RTV-8900, the 2.5amp fast blow was a poor choice. I'm sure UL put the motor into a stall at full speed to see what current it drew and it had to blow it's fuse in a specified time. That has no practicality in real life. The slow-blow fuse will stop your fuses from blowing. The 3-amp will give you a margin. The 2.5 amp fast blow was simply a bad design and should be rethought.
Steve
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"Old projectionists never die, they just changeover!"