Realistic TRC-427 'GoldFinger' Audio Mod Locations
for the neophyte
RX:
C33 = 2.2uF Mylar or Polypropylene
C62 = 2.2uF Non-Polar Electrolytics or Mylar
C63 = 2.2uF Non-Polar Electrolytics or Mylar
C76 = 1,000-2,200uF 25 V Electrolytic
D7, D8 = 1N6263 Schottky Diodes
Tr2 = "First Receive Amp" Location
leave Tr2 alone.
TX:
C66 = .22uF, or .068, or .033 Mylar (Lower Value = Less Bass)
C124 = .001uF Ceramic Disc or Mylar (Maybe try .01 instead)
C130 = 1.5uF - 2.2uF Tantalum Capacitor (+ side to base of TR18)
R99 = Stock Value is fine at 3.3K (Mic Audio input), could lower to 2.2K, but no factory mic gain control..
**C132 = 22uF
Inspired by: GoldFinger of WWPDX
Written up by: LeapFrog of WWDX
Hope someone gets some use from this, just to clarify these are the "GoldFinger" cap change locations for the
Realistic TRC-427, you can go wild changing
transistors if you want (TR11, TR18), but this is just a basic cap change process for beginners..
I don't have time to run a frequency sweep, but if you own one of the these radios and try the mod, it will make a measurable difference.
DISCLAIMER: **Remember to follow all rules and regulations where you live & operate**
Best of Regards & Enjoy!
-LeapFrog
for the neophyte
RX:
C33 = 2.2uF Mylar or Polypropylene
C62 = 2.2uF Non-Polar Electrolytics or Mylar
C63 = 2.2uF Non-Polar Electrolytics or Mylar
C76 = 1,000-2,200uF 25 V Electrolytic
D7, D8 = 1N6263 Schottky Diodes
Tr2 = "First Receive Amp" Location
leave Tr2 alone.
TX:
C66 = .22uF, or .068, or .033 Mylar (Lower Value = Less Bass)
C124 = .001uF Ceramic Disc or Mylar (Maybe try .01 instead)
C130 = 1.5uF - 2.2uF Tantalum Capacitor (+ side to base of TR18)
R99 = Stock Value is fine at 3.3K (Mic Audio input), could lower to 2.2K, but no factory mic gain control..
**C132 = 22uF
Inspired by: GoldFinger of WWPDX
Written up by: LeapFrog of WWDX
This radio is very similar to the PC-66, 21 GTL, and 25 LTD radios.
The Realistic TRC-427 used a PC-392AB, or the PC-392AD PCB revision depending on year.
manufactured by Uniden in Korea & Taiwan for Tandy/RadioShack during the late 70's.
As a rule of thumb: if it's not NIB mint, I swap in a Cobra/Uniden 4-Pin style mic jack for these radios.
It's a real talker after this mod, I used a "medium fidelity"
(Fet modded) amplified D104 and even tried a stock Galaxy hand mic, the SDR samples sound great.
Of course the modulation transformer will have a frequency roll off of what it can pass, high & low,
so whatever audio gets fed into the pre-amp and amplified by the high-level audio I.C. (stock TA72222AP)
will ultimately be "choked" at the transformer.
An AM regulator mod
(I call it the Wabi-Sabi) remedies that and allows the radio to go WIDE..
with an optional External input control, but that's for another post...
Hope someone gets some use from this, just to clarify these are the "GoldFinger" cap change locations for the
Realistic TRC-427, you can go wild changing
transistors if you want (TR11, TR18), but this is just a basic cap change process for beginners..
I don't have time to run a frequency sweep, but if you own one of the these radios and try the mod, it will make a measurable difference.
DISCLAIMER: **Remember to follow all rules and regulations where you live & operate**
Best of Regards & Enjoy!
-LeapFrog
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