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Re: [Amps] L4B Caution

To: "Ed K0KL" <edk0kl@centurytel.net>, <amps@contesting.com>, "Paul Baldock" <paul@paulbaldock.com>
Subject: Re: [Amps] L4B Caution
From: "Jim W7RY" <w7ry@centurytel.net>
Reply-to: Jim W7RY <w7ry@centurytel.net>
Date: Thu, 25 Jul 2013 11:52:18 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
And provide the ALC voltage. If you don’t use ALC (which I don't) then you can remove them.

73
Jim W7RY


-----Original Message----- From: Paul Baldock
Sent: Thursday, July 25, 2013 10:41 AM
To: Ed K0KL ; amps@contesting.com
Subject: Re: [Amps] L4B Caution

I suggest you remove the bleeder resistors. They serve no purpose
other than to speed up the bleed down when you turn the amp off. They
create a lot of unnecessary heat in the supply.

- Paul   KW7Y



At 10:32 AM 7/25/2013, Ed K0KL wrote:
I had a bad experience when working on an L4B for a pal. The bleeder resistor mounting scheme proved to be a little poor (unusual for Drake). When reinstalled, one of the resistors
shorted to the mounting screw.
This bleeder is held in place by a screw that goes through the center of the resistor. Mica slices insulate the ends (chassis and screw head). Only thing is the resistor arced through the ceramic base material. So I used glass tape to insulated the screw on the reinstalled components. This
provided better spacing to the center of the screw.
Note- I replaced the resistors, having the same thing reoccur. Only with the use of the tape did the thing calm down. Ordinary electrical tape won't work as it will melt caused by the heat of
the resistors.

Anyway, that was some time ago, the amp is going strong. Except for a rather weak plate
transformer, this puppy will no doubt last several lifetimes.
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