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Re: [Amps] L4B startup after a long sleep?

Subject: Re: [Amps] L4B startup after a long sleep?
From: Stan Gammons <>
Date: Tue, 11 Dec 2018 22:42:33 -0600
List-post: <>
I would set the meter to grid current and use a variac to first power it up. Unless you have a 240 volt AC variac, you may have to rewire the power supply and RF deck for a 110 volts AC variac. There might be a loud bang if one plugs the amp in and just turns it on. Tubes could be gassy from setting so long and arc over when full plate voltage is applied.

Harbach makes a replacement power supply board for the L-4B and the L-7.  I think that board is what I have in my L-4B power supply.

Good luck with the amp. The L-4B is a nice old American made amp.



On 12/10/18 4:53 PM, Ray LaRue wrote:
The local club here has inherited a very nice L4B amplifier that we suspect hasn't been run in about 10 years or more.  On a scale of 1 to 10 with 10 being new, this is a very nice 9.  I have been asked to reform or replace the filter caps and bring it up on line.

As I've never worked on an L4B, I would appreciate any experienced tips or no-nos, as I begin to dive into it.

Any assistance would be appreciated.
Ray, W4BYG

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