PK-232 Noise Cure

    Several AMTOR bulletins by TG9VT, ZS6AQC and others have
explained a simple modification which allows the PK-232 to
copy much weaker signals in all modes than was previously
possible.  All who have completed this modification report
results which can only be summed up as amazing.  Basically the
modification consists of adding bypass capacitors directly
across the power supply pins of all op-amp filter IC's.
    This removes troublesome power bus noise, produced by
other circuits within the unit, which tend to interfere or
cover-up weaker signals.
    I have added some details to allow a somewhat clearer
explanation of the basic mod, but full credit should go to the
     Naturally, any modification to a unit under warranty will
void that warranty, so beware.
     1.) Kill power, remove all cables label them if necessary
electrostatic handling precautions must be utilized.
     2.) Remove the top cover by removing all six cover
screws, side and rear.
     3.) Remove the knob on the threshold control along with
the nut which fastens the threshold pot to the front cover.
     4.) Remove the entire PC Board by removing all 6
fastening screws.
     5.) With the front of the board facing you, locate U-23,
an MC34074-P, on my unit (S/N 21186) all of these type chips
are colored shiny black and marked "JRC" as opposed to a flat
black type packaging on all other IC's.  In addition, all of
the chips addressed by this mod are on the right hand half of
the board.  Flip the board over and mark the socket with a
felt tip type pen.  Also mark pins 11 and 4 which are adjacent
to each other.  Continue this same procedure with U-26, 28,
30, 32 and 34.

GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information