Philco 37-3640 / 37-640 questions - Printable Version
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+--- Thread: Philco 37-3640 / 37-640 questions (/showthread.php?tid=17173)
Philco 37-3640 / 37-640 questions - SBERG - 08-21-2017
My first commitment on this forum. Up to now, I was just reading and learning. Great community.
I just bought a couple antique radios from my brother-in-law. The radio that I am currently working on is a Philco 37-3640. Don’t look for it. It is a Canadian model.
The receiver is made in Toronto and is in fact a 37-640, well documented on yout site. I have the original schematic of the 37-3640 and all available information for the 37-640.
The cabinet is made by Victoriaville Furniture, Victoriaville, Quebec, Canada. No picture on the net exactly matches this cabinet so, I will share some whem I will found how to do it ;-)
[Image: https://1drv.ms/i/s!AqDzjKUOhlam2wbYZMxTyBMexU8W]
I did some basic work (cleaning, visual check, short circuit check and replacing the power supply caps) and I can confirm that the radio is functional. Reception looks quite good. I now working an overall check starting with the power supply section. This is the reason of my questions here.
- There is a 2ohm resistor that shunt the 25 ohm part of the resistor in location 68 (may be a previous repair). This lower the bias voltage from -3.3V to -0.25 Volt. The change adds a lot of sensitivity to the receiver. If I disconnect it, reception is quite bad.
Have you seen this change before?
- On capacitor in location 66A, I read -22 Volts referred to ground/casing.
Is it the correct voltage polarity? In that case, the schematic shows the wrong polarity for the condenser and I need to swap my condenser.
Edit: Image added by admin
RE: Philco 37-3640 / 37-640 questions - klondike98 - 08-21-2017
Welcome to the Phorum!
Nice looking set!
For those who might be able to answer your questions...here's the link to the 37-640 schematic.
RE: Philco 37-3640 / 37-640 questions - SBERG - 08-21-2017
Thanks to the moderator to have added my picture.
See the schematic of the 37-3640 below. A re-organized version of the 37-640.
And a few more pictures of the receiver.
Cabinet plates
Receiver
RE: Philco 37-3640 / 37-640 questions - Radioroslyn - 08-21-2017
Hi and welcome,
>Is it the correct voltage polarity?
In this situation the + side is connected to the chassis and the - goes to the center tap of the HV winding on the power transformer.
I'll mention if you have an electrolytic capacitor that has been connected backwards do not reuse it, chuck it it's shorted.
RE: Philco 37-3640 / 37-640 questions - SBERG - 08-24-2017
I am closing this projet for now. Below is what I did, for reference. Hoping can that help someone - also valid for a 37-640 I guess.
I did minimal restore and checks 1) was my first introduction in radio restauration 2) I don't want to risk breaking something as fragile as the dial disk 4) the design and assembly of this radio is quite complex 3) replacing all caps and resistors would let's me feel that is no more the same old radio...
Finally, the radio works and perform quite good as is. Not a lot of humm, and I get a lot more radio stations than before. Will see in the future. I have a RCA M46 and M46A to practice - simplet in their design and assembly.
Will rather improve the antenna for now.
RE: Philco 37-3640 / 37-640 questions - Radioroslyn - 08-24-2017
You may want to consider replacing #61,44,52,60,64,20, and 14. These are in the HV path and if leaky can cause excessive HV current. 41 and 43 are a good idea they can effect the tonal quality or cause noise.
RE: Philco 37-3640 / 37-640 questions - SBERG - 08-27-2017
Thanks a lot for your suggestions. Most seem quite easy to replace. I will certainly work this when I will do another restoration pass.