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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