Film-Tech Forum ARCHIVE: Dead LP-270

This is topic Dead LP-270 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Dominic Espinosa (Member # 2122) on 11-06-2008, 06:12 PM:

So this afternoon I come in to open up one of our theaters and find that whomever closed the night before had depressed 2 of the 4 mode switches for the bottom platter on one of our LP-270's.
I managed to push/pull/wiggle one of the switches out, all switches now depress and pop out as they're intended.
However, the platter was completely dead. I checked the fuse under the select switch cover which was fine however the 5 Amp fuse in the bottom of the column was blown.
Swapped it out but it just popped again.

My thought is that the contacts inside one of the buttons is still engaged. Thoughts?

EDIT: Did some searching -- could this be a diode issue resulting from the button press?

Posted by Steve Guttag (Member # 268) on 11-06-2008, 06:58 PM:

Yes...all but the most old platters use an octal plug with either 4 diodes inside or a square-pack bridge rectifier mounted in the octal socket.

Another possibility is that the switch bank in question remains bad and is causing a short circuit. I'd start with the bridge rectifier though.

Steve

Posted by Monte L Fullmer (Member # 2797) on 11-06-2008, 11:35 PM:

I ran a booth with four LP-270's and had two that would love to blow the fuses which did turn out to be that plug-in diode would be shorted.

Never could figure out why of the diodes would short out unless we had some crazy voltage come swinging into the building.

One changeout and it'll behave for good on one unit, while the other unit would take out a diode set twice or more in a year.

Posted by Dominic Espinosa (Member # 2122) on 11-07-2008, 02:07 PM:

Interesting. Thank you both for the input on this situation.
We ended up getting back up after I called our resident guru who has had more experience with these than I and happened to have a spare diode stashed at the theater.
I had assumed we didn't [Wink]

Interesting on your note, Monte, we had a power outtage 2 days ago -- wonder if that contributed to this issue as it did cause a small amount of havoc with our computers -- or so I'm told...

Posted by Steve Guttag (Member # 268) on 11-08-2008, 07:59 AM:

If you want to virtually eliminate the diode failure, try putting a suitably sized MOV across the AC input to the bridge.

Steve