Philco 70 - Printable Version

Philco 70 - Printable Version

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Philco 70 - dkelsea1 - 10-22-2025

Hello,
I'm working on a Philco model 70 and the choke resister looks burnt. Does anyone know what the resistance of the different legs are? Also the size wire used in case it needs rewinding?. I realize a very tedious task but I think I can do it. Does someone out there provide this service?
Dave

RE: Philip 70 - radiorich - 10-22-2025

Hello Dave,
I wanted to welcome you to the forum and I am sure someone among the forum will know your answer .
Sincerely Richard

RE: Philco 70 - klondike98 - 10-22-2025

Welcome to the Phorum!
Icon_wave

In our digital library we have two annotated schematic versions of the Model 70, for the "early" and "later" versions. Perhaps that will help:

https://philcoradio.com/library/index.php/service-info/early-schematics/

RE: Philco 70 - morzh - 10-22-2025

OK, which one do you mean? DO you mean the choke (it is not a resistor but an inductance) or some resistor?
Is this the one shown on both sch Bob has listed as #39?

RE: Philco 70 - Arran - 10-22-2025

Do you mean the voltage divider resistor, a large wire wound resistor, with taps, mounted on a metal rod, (part #37 or #36) or do you mean the filter choke? (part #39)
Regards
Arran

RE: Philco 70 - MrFixr55 - 10-22-2025

Hi dkelseya1,

First off, Welcome to the Philco Phorum! A phamily phriendly phorum, phull of phine phun phriendly pholks phull of phine Philco phacts! (See a pattern here?)

Please take the time to review the Phorum's rules and regulations and please read the post "What not to post in the Phorum". Also please take the time to "introduce yourself" in the "Introduce yourself" forum category. Don't forget to visit "Old Ron's Bar and Grill, belly up to the bar for a virtual burger and brew, and to shoot the breeze.

Now, to your radio. Please note that there are 2 versions of the Model 70, quite different from each other. You need to determine which one that you have. If the S/N is missing, look at the volume control. If it has only 3 leads and connects between the detector and AF amp, you have the later model. If your volume control has 2 sections, 6 lugs with one section across the antenna and the other section connected to the voltage divider resistor, you have the older set. The major differences between the older and newer sets are:

The older set has separate oscillator and mixer tubes. The newer set uses an "autodyne" oscillator-mixer circuit using only one tube.
The older set lacks AVC (Automatic Volume Control), therefore the volume control controls the signal strength and cathode bias for the RF and IF tubes. The newer set has AVC, therefore the volume control is in the more familiar position, varying the strength of signal to the 1st audio amp.

By "choke resistor" do you mean the "voltage divider resistor", a multi-tapped wirewound resistor, or are you actually referring to the filter choke? The voltage divider resistor is referred to as#37 on the older set and #36 on the newer set. The filter choke, an inductor with only 2 leads, is denoted as # 39 on the older set and # 52 on the newer set.

If you are referring to the resistor, this resistor does not have any value as an inductor; it is intended only as a resistor and open sections can be replaced by individual resistors (I recommend 10 watt units), or the entire resistor can be replaced with individual resistors. The resistance values are listed on the schematic.

Please note that if this is the older set, the resistance between Pins 3 and 4 (letters F and G) should be 250 Ohms and is the resistance of the cathode bias section of the volume control.

Please ensure that you replace all the capacitors in this set, and verify all resistance values.

Hope this helps!