Telex Intercom System issue...

Wtw2545

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Feb 16, 2016
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Missouri
So I have a 5 line Telex BP-1000 system and two SS-1002 powered by a PS-1F yesterday during our dress rehearsal we started getting a screeching and static type sound in all of the headsets and none of us could talk on them. I checked everyone's connections and they were fine the only thing that helped was when I disconnected the power supply from the sound systems sequencer and connected power directly from the wall which let us talk and lowered the static and screeching sound. The system is a little old and I think that the power supply is going out...Any ideas or suggestions to fix it other than replacing it?
Thanks
 

MNicolai

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The PS-1F is rated for 4 beltpacks. My guess is that you've overdriven the power supply and a component inside of it like a capacitor has blown up. Unlike the larger power supplies that detect an overload and shut down to protect it until the fault is cleared, I expect the PS-1F might just keep plowing along until it overheats and starts wigging out.

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The first thing I would check -- ONLY with the power disconnected to the unit, is to open it up and visually inspect the components. Should be pretty obvious from smell or sight if something is scorched. If so, it shouldn't be hard to fix but would prove the system's been operating with too many devices attached to it and that it's time to upgrade to a larger power supply.

My second inclination is that if swapping the power source reliably removes the problem, you may have a short to ground somewhere. I would pull open any/all wall plates you have intercom jacks at and visually inspect that none of the shields on the cabling have become shorted to the conduit or back box. Could be a wire was stripped back too far or during a wire pull a wire was dragged over a conduit end and the cable jacket got nicked. In this case, it could just be that in the time it took you to troubleshoot and swap power sources, the power supply cooled down a little and it wasn't actually the source of power that was causing the noise.
 
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FMEng

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That's a very simple, linear power supply. It has three capacitors that fail with age and heat exposure. Replace those three $0.50 components and most likely it will be as good as new.

The three terminal regulator has over-current protection. The noises are the regulator going into oscillation because the bypass capacitors aren't doing their job. Cutting the power momentarily breaks or changes the oscillation.
 

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