66X3 Ch= RC-1038

RCA (RCA Victor Co. Inc.); New York (NY)

Data
Forum
Pictures
Collections

  • Year
  • 1946
  • Category
  • Broadcast Receiver - or past WW2 Tuner
  • Radiomuseum.org ID
  • 53657
    • alternative name: RCA Manufacturing || Victor Talking Machine

Click on the schematic thumbnail to request the schematic as a free document.

 Technical Specifications

  • Number of Tubes
  • 6
  • Main principle
  • Superhet with RF-stage; ZF/IF 455 kHz
  • Wave bands
  • Broadcast and Short Wave (SW).
  • Power type and voltage
  • AC/DC-set / 105-125 Volt
  • Loudspeaker
  • Permanent Magnet Dynamic (PDyn) Loudspeaker (moving coil) - elliptical / Ø 6 inch = 15.2 cm
  • Power out
  • 1.5 W (unknown quality)
  • Material
  • Wooden case
  • from Radiomuseum.org
  • Model: 66X3 Ch= RC-1038 - RCA RCA Victor Co. Inc.; New
  • Shape
  • Tablemodel, low profile (big size).
  • Dimensions (WHD)
  • 15.3 x 9.3 x 7.3 inch / 389 x 236 x 185 mm
  • Notes
  • Pilot lamp: Mazda Nº 1490, 3.2V.
  • External source of data
  • Ernst Erb
  • Circuit diagram reference
  • Rider's Perpetual, Volume 15 = 1947 and before
  • Literature/Schematics (1)
  • RCA Victor Instruments Service Notes 1946

 Collections | Museums | Literature

Collections

The model 66X3 is part of the collections of the following members.

 Forum

Forum contributions about this model: RCA RCA Victor Co.: 66X3 Ch= RC-1038

Threads: 1 | Posts: 7

I recently purchased an RCA 66X3 AM/SW reciever from eBay. It initially had the normal bad capacitors and several >20% out of tolerance resistors. Tubes tested OK with perhaps the RF amp (12SG7) a little weak but good. Tune up seemed to go OK, but the SW band was definitely poor with a lot of extraneous mixes on the dial that appeared to be from nearby FM stations. Sensitivity and volume was very low.

I have a battery operated o'scope and discovered that the LO seemed to be on the AVC circuits and on the circuit ground of the 12SQ7 resulting in LO on the plate of the RF amp. This situation only exists while in SW. The regular AM broadcast band is actually quite good and there is no LO on the RF amp or AVC.

I am wondering if anyone else has experienced this problem and what they did to correct it. I have had some emails with other less technical owners and they state that their sets are also weak on SW but I don't have any information on strange mixes in their sets.

Update: I found that bypassing the circuit ground of the 12SG7 (B-) to chassis did not affect the level of LO signal on the plate. LO signal on the pin 8 (signal in) of the 12AS7 (mixer) is 180° out of phase with the LO on pin 5 (osc). This must have something to do with the band switch, but contacts appear to be OK. The band switch shorts out a section of the oscillator coil to B- rather than switching in a different coil. B- comes to the bandswitch via an insulated braided cable (like the shield off of a piece of coax) and LO (12mHz) signal can be seen on the cable. Once the LO signal is coupled onto the AVC circuit, it is present on the grid of the 12SG7 (RF amp) which makes this one of those "chicken or egg" questions. 

Fred Neudecker, 02.Dec.13

Weitere Posts (7) zu diesem Thema.