To: K7SX@worldnet.att.net, amps@contesting.com
Subject: Re: [AMPS] mods L-4B
Message-ID: <19970406.190404.9983.2.km1h@juno.com>
References: <19970406194611.AAA5976@davida.utw.com>
X-Mailer: Juno 1.15
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To: <amps@contesting.com>
Date: Sun, 06 Apr 1997 20:01:56 EDT
On Sun, 6 Apr 1997 13:45:31 -0600 "David McPhie" <K7SX@worldnet.att.net>
writes:
>Does anyone know of a list of modifications to the Drake L-4B amp and
>or
>its power supply?
> I would like to add a L-4B to my C line.
The only RF deck change that I am aware of is using 3-500Z's in place of
3-400Z's in the early L-4B's.
The PS is a weak link in an otherwise fine amp. Simple improvements would
to be change the diodes to 1N5408's and remove the diode equalizing
resistors; they are not needed with modern diodes. A muffin fan is
another great improvement.
If you are willing to go thru the hassle of getting around all the
interlock crap; check the voltage drop across each electrolytic; they
should all be within 10-20V of each other. If not start troubleshooting
by checking the capacitor equalizing resistors for 100K at 5% tolerance.
If even a few are off replace with modern 3W metal oxide resistors.
GL and 73; Carl KM1H
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