RCA Q36 Receiver

Restoration of Model Q36 RCA Radio



Author: Edgardo Castro Bruse
Author: YS1ECB
AUGUSTO EDGARDO CASTRO BRUSE
Calle Loma Linda
Residencial Loma Linda casa No. 4
Col. San Benito.
San Salvador. El Salvador.

San Salvador, April 6, 2014



Introduction

This radio was a gift, given to me by my friend Dr. Fernando A. Melgar several years ago. When I received the radio it presented distorted audio, the magic eye did not work, but its shortwave reception was very good. RCA Q36 Radio, 1947
RCA Victor corp. USA Year: 1947/1948
Type: Broadcast Receiver
Valves/Tubes 11: 6SG7 6SA7 6SA7 6SK7 6U5 or 6G5 6SQ7 6R7 6SK7 6F6G 6F6G 5U4G
Principle Superhet with RF-stage; ZF/IF 455 kHz
Wave bands Broadcast plus more than 2 Short Wave bands.
Power type and voltage Alternating Current supply (AC) / 105-125/100-260 Volt
Loudspeaker Electro Magnetic Dynamic LS (moving-coil with field excitation coil) / Ø 8 inch = 20.3 cm
Power out: 10 W
Wooden case, tablemodel, low profile.
Dimensions (WHD) 625 x 375 x 325 mm / 24.6 x 14.8 x 12.8 inch
Notes Bands: BC, Police, 5xSW spread band.
Net weight: 22.3 kg / 49 lb

RCA Q36 schematic diagram


Repairing the Radio


The audio distortion was due mainly to two causes:
  1. The 6R7, a medium mu tube, had been substituted by a 6K7, a high mu tube.
  2. A shielded cable, disconnected from ground, automatically disconnected a resistor grounded through this cable´s shielding.


The ground connection was restored by means of a wire.
Since a 6R7 could not be found, a tube adapter was built in order to use a 6BF6 to replace the 6R7 original tube.
The "magic eye" was replaced by a new one, and to prevent a fuzzy image, the cathode pin of the 6U5 must be connected to the grounded lead of the 6U5´s filament.
Finally a complete recapping of the radio was done. Now the radio works in an excellent way! Under Chassis of Q36 "Before" and "After" Restoration. Please click on images to enlarge

Chassis of Q36

RCA Q36 before restoration

RCA Q36 chassis before restoration RCA Q36 chassis old radio RCA Q36 chassis RCA Q36 chassis before parts replacing old radio RCA Q36 before parts replacing
old radio RCA: before parts replacing Q36 inside view Q-36 components before RCA Q36 chassis components before replacing RCA radio 1947


RCA Q36 chassis after restoration

RCA Q36 Radio restoration RCA Q36 Radio chassis RCA Q36 Radio parts RCA Q36 Radio chassis


6BF6 Adapter and Chassis. Please click on images to enlarge
RCA Q36 vacuum tube adapter 6BF6 Adapter 6BF6 tube Adapter RCA Q36 chassis up
RCA Q36 6BF6 tube adapter 6BF6 tube adapter RCA Q36 chassis general


Reassembly of Q 36 into its Cabinet

It is important to follow the sequence shown by the pictures, in order to install easily and correctly all parts into the cabinet.
RCA Q36 cabinet restoration RCA Q36 loudspeakers RCA Q36 loudspeakers RCA Q36 loudspeakers RCA Q36 grill cloth
old radio RCA: cabinet Q36 cabinet inside view Q-36 cabinet box RCA Q36 cabinet restore RCA radio 1947 cabinet
old radio RCA: cabinet parts replacing Q36 inside view Q-36 mount and secure speakers RCA Q36 chassis components cabinet replacing  


Final view of restored RCA Q36

RCA Q36 restoration completed RCA Q36 after restoration RCA Q36 restored



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