Film-Tech Forum ARCHIVE: Holmes Amplifier L25N

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Topic: Holmes Amplifier L25N

Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999

posted 08-28-2000 02:41 PM

John Anastasio gave me an original Holmes amplifier that he didn't need anymore. I am wondering if anyone that reads this is old enough to know who built this amp for Holmes?

This amp has a burned out output transformer. The secondary winding is out. I've got a transformer from a 6L6 amp tacked into the circuit, and I have sound. I'll be getting caps for this amp shortly.

I have a major thanks to John for letting me at this thing. I will use this amp when I start running my 3rd rebuilt Holmes (an Educator with the governor controlled Bodine motor) That one will be another topic entirely.

Thank You John!

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Ken Layton
Phenomenal Film Handler

Posts: 1452
From: Olympia, Wash. USA
Registered: Sep 1999

posted 08-28-2000 02:58 PM

Amp was probably built by Altec-Lansing.

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Bruce McGee
Phenomenal Film Handler

Posts: 1776
From: Asheville, NC USA... Nowhere in Particular.
Registered: Aug 1999

posted 08-28-2000 06:36 PM

I was not inferring anything about your age, Ken, but, I had you in mind when I posted the question.

The amp has run about an hour this afternoon. There is some hum, and there is distortion in the mic input using a real crystal microphone that I borrowed from a radio collector friend who vouched for its good working condition.

I felt the 90v supply for the photocell when I brushed my finger over it, so I guess it is working.

The voltages I am getting are within acceptable ranges of what is in the manual that I got from Film-Tech.

Ken....Didn't it come from you, originally?

Now that it is dark, I am running the amp as I type this. The outputs have that nice blueness around the grids that I like so... I have hooked a small speaker up so I can hear any problems as they might happen.

The date printed on the schematic in the bottom of the amp is 11-27-42.

I love old tube stuff.

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John Eickhof
Jedi Master Film Handler

Posts: 588
From: Wendell, ID USA
Registered: Jan 2000

posted 08-28-2000 11:27 PM

Actually Holmes built their own sound equipment based on western electric designs. The L-25-N was optional for most Holmes set-ups and was stock on the type D system built for the Navy. Experiment with the resistance value across the input of the transformer by 10% either way and see if this remedies the distortion. Also, if the bridging capacitor in series with that resistance is bad (most likely) distortion and low volume will occur. This can also cause doubling of the plate voltage and transformer failure. Good luck!!!

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