CANADIAN MARCONI HOME ENTERTAINMENT -  MODELS 141 and 144

Type:  8 tube, superheterodyne receiver with six pushbuttons for preset tuning..
Frequency range:

530 to 1725 KHz
5500 to 13500  KHz
13400  to 22400 KHz
Vintage: 1938

Tube lineup:  6A8, 6K7, 6H6, 6F5, 2 x 6F6, 5Y4, 6G5
Audio power: 4.5   watts
Speaker: 12 inch electrodynamic

Input power: AC 115 VAC 60 Hz, 80 watts
                                          25 Hz  81 watts

COMMENTS:

Differences in part numbers between models 141 and 144 affect the speaker , power transformer and cabinet.

Cabinet

The 141 cabinet has two wooden spindles on the front, below the pushbuttons. The model 144 has three skinny slats between the two spindles..  It is believed that this is the leading difference between the model 141 and 144. In each model, the speaker appears to be 12 inches in diameter
One type has the audio output transformer mounted on the top portion of the frame while the other type has it mounted on the bottom of the frame..

Indicators

The hole adjacent to the top right of the dial is for the 6G5 magic eye tube. It attaches to the cabinet and is connected to the chassis with a  cable terminated with a female socket at the tube end. The other end is hardwired to the chassis. The hole to the top left of the dial has a green transparent disc that reads AUTOMATIC. When the band switch is moved to the AUTO position, two things happen. First, the AUTOMATIC lamp is illuminated to let the user know that frequency selection is by pushbutton. Then, depending on which pushbutton is selected, a different  pair of variable capacitors are connected to the Mixer and Oscillator stages so the new station will be heard.

The 12 variable capacitors needed for the pushbutton function are located on the rear apron of the chassis. To retune any pushbutton to a ew station, the user would first have to select AUTO, then deprtess one of the buttons then adjust the oscillator capacitor to the new frequency; Next, the corresponding MIxer stage capacitor would have be adjusted for maximum signal strength. When in AUTOMATIC mode, the main tuning capacitor does not have any effect.  To get back to main tuning, the band selector switch is moved to any of the other positions. other than Automatic.

The pushbutton assembly p/n 67632 is called the "Automatic Tuning Unit" in the parts list and is not identified on the schematic.

Power Transformers

The schematic shows two different part numbers for the power transformer - one part number is for 25 Hz while the other is 60 Hz. Yet the nameplates for both the model 141 and 144 show 25/60 Hz operation. It is believed that the models 141 and 144 would have to be fitted with a 25 Hz transformer in order to operate at 60 Hz. With transformers, a 25 Hz unit will operate at 60 Hz with no problem but a 60 Hz transformer will start to overheat if used at 25 Hz.

The 141/144 service bulletin from the Canadian Marconi service manual can be viewed here

MODEL 141  PHOTOS

141_02.jpg
Model 141 front view
141_03.jpg
Model 141 rear view. Note that the auto output transformer is mounted to the top of the speaker frame . The shield over the field coil is also missing.  
141_04.jpg
Model 141 nameplate.
All photos in this table by Matt Flesch

Model 144 Photos

144_01_front.jpg
Model 144 front view.
144_02_rear.jpg
Model 144 rear view.
144_03_speaker.jpg
Model 144 electrodynamic speaker. The auto output transformer is mounted at the bottom of the speaker frame. This likely accounts for the two speaker part numbers, 
144_04_nameplate.jpg
Model 144 nameplate.
All photos in this table by John Fera
Section 3 of the schematic needs clarification. The unlabelled lights provide left and right side dial illumination. The two arrowheads connect to the arrowhead on the 6.3 volt filament winding of the power transformer. The other lights are labelled (L-R) BCST, MW, S/W and AUTO.
 
Contributors or References:

1) Canadian Marconi Service Manual Vol 1.
2) Matt Flesch   <ma_ttf15(at)hotmail.com>
3) John Fera <cca394(at)gmail.com>
4) Jim Brewer <snack.235(at) sympatico.com

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Sept 6/17