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Philco 70
#6

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!

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
Philco 70 - by dkelsea1 - 10-22-2025, 01:51 AM
RE: Philip 70 - by radiorich - 10-22-2025, 10:09 AM
RE: Philco 70 - by klondike98 - 10-22-2025, 12:04 PM
RE: Philco 70 - by morzh - 10-22-2025, 01:19 PM
RE: Philco 70 - by Arran - 10-22-2025, 06:18 PM
RE: Philco 70 - by MrFixr55 - 10-22-2025, 11:22 PM



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