8mm Forum: White Noise & Hot Power Cord in B&H 202

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Topic: White Noise & Hot Power Cord in B&H 202

Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted December 10, 2006 07:57 PM

I have very clean B&H 202 mag/opt projector. Everything works, but the power cord get very hot and there is white noise in the sound. I cleaned the volume and tone pots. Should I spray the tube sockets also? Could this white noise be a tube or capacitors, etc.? Why the hot power cord?

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted December 11, 2006 10:57 AM

Does the power cord get hot if the amp only is on or just when the projector is running? If the latter, it's probably just the 1000 Watt lamp. Don't use an extension cord and make sure the outlet is a 20 amp service.

As for the white noise, does it vary if in mag rather than optical? The phototube has a higher noise level than the mag, but white noise is something that was common to tube amps, it's just a matter of how much. Noise can come from many sources. The phototube, the exciter lamp supply, noise from controls and resistors. Usually higher value resistors have potentional for problems than lower values. Resistors go up in value with age, capacitors go down in value with age.

Also check filter capacitors in the amp. Also in this amp (I don't recall the schematic) is the heater circuit ac or dc? Amps with ac on the heaters in the preamp stage have more noise than those with dc. Also a bad filter capactor if it's a dc heater will allow more noise.

John

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Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted December 12, 2006 11:27 PM

Thanks, John, I'll trouble shoot using your advice and post my findings.

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