The PHILCO Phorum
52-942 - Printable Version

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52-942 - Ken Arroyo - 06-05-2025

Just received my 52-942. Its a handsome set. When I opened the back to examine it I noticed there are not connecting wires from the loop antenna to the 4-prong socket in the back of the chassis. What size wires could I use that will fit snugly and serve to make the connection from the loop to the radio itself?
Thanks!

RE: 52-942 - GarySP - 06-05-2025

Welcome to the Phorum, Ken! The included schematic for your set is located in the Philco Library at the bottom of our Home page.
https://philcoradio.com/library/index.php/service-info/philco-1952-home-radio-year-book/
It has a detailed photograph of the Loop/Plug wiring of your set. Do you have the plug for the antenna? If so, you could make the harness out of 16, up to 20 Gauge insulated multi-strand copper wire. If you could add a photo of the back/loop as well to help determine next steps. Plenty of help is available here to get your radio back in action! Take care, - Gary

RE: 52-942 - Ken Arroyo - 06-05-2025

Unfortunately, I don't have the plug. Here's a screenshot of someone else's 52-942's back cover. I don't suppose it would be too difficult to just run wires from the inside of the chassis through the socket openings to the back. Just more work. I was rather surprised to see how Philco does this. None of my RCA's or Zenith's use plugs like this. They just use long enough wires to the back, and you simply have to be careful!

RE: 52-942 - Ken Arroyo - 07-02-2025

This Philco has me baffled. Without the antenna plugged in it receives 940 khz, the strongest local station, albeit weakly, with much noise in the background. The station appears exactly where it should on the dial.
Earlier in this thread I may have mentioned that this radio has a four prong jack for the antenna. The matching plug and wiring was missing from the back cover/loop antenna, so I made some "plugs" from the pins of an old 12sk7 tube. I only made two plugs as the other two are dedicated to an external antenna connection and ground. But when I plug in the loop all I get is loud BRRRR noise, like the noise a bad filter cap would make. But that makes no sense as this radio has been completely recapped!
I need some ideas or this one is going out with the bulk trash pickup at the end of the month.

RE: 52-942 - morzh - 07-03-2025

I will delete the other thread.

RE: 52-942 - MrFixr55 - 07-03-2025

Hi Ken,

My previous post went Bye-Bye. Don't trash it, fix it. If you do want to trash it, place an ad in the for sale section, someone wil find a good home for it.

This is not a horribly complex radio, don't give up!

Before going further, please note that this is a "warm chassis" set and that the power switch is in the B- / Filament return leg of the power line. Radio manufacturers have been doing this for years. With this leg of the power line connected to neutral, the chassis, through a 0.1uF cap and a 150K resistor, is also at neutral potential. Now, when the power switch is turned off, the chassis now floats to 120V through the cold tube filaments. Many of us move the switch to the "Hot" side (the rectifier plate and filament) and install a polarized plug.

Try the following:

If you have a similar radio, use it to determine the "environment" where you are repairing and testing the radio under question. Fluorescent, CFL and LED lighting, computers, monitors, UPS units, WiFi, 5G cell phones, digital TVs, the Internet of Things (Alexa, doorbell cams, Bluetooth, etc.) have wreaked havoc on the AM band. Use a radio that has an antenna loop but not a ferrite loopstick.

Review your work and ensure that the correct value parts were properly connected. Pay close attention to C9, a 0.05uF cap between the AVC line and B-. If this cap is not properly installed, you will get a "Motorboat" sound.

Disconnect the antenna and ensure that you are using the right pins on the antenna socket. One of the pins (Pin 2) connects to the speaker. Connecting the return of the antenna to that will generate all sorts of fun noises from feedback! Pin 4 goes to the stator of the RF Amp section of the tuning cap and pin 6 (grid) of the RF amp tube. Pin 1 goes to the AVC line through the 2.2 meg resistor R. However, I wonder if this is a mistake. On any other radio whose schematic I reviewed, the return of the loop antenna is directly to the AVC line (the frame of the tuning cap) and this 2.2 meg resistor does not exist. There is a 2.2 meg resistor between the detector output or AVC plate and the AVC line. This circuit develops a negative bias voltage depending on the strength of the signal. Try moving the connection to the stator and frame of the tuning cap.

Also, try to connect pin 3 (chassis ground) as per the instructions on the schematic. This may be necessary for stability, especially if you leave R1 in the circuit.

Check lead dress and position for all caps. A cap too far away from the chassis or too close to a tube socket could cause oscillation.

Hope this all helps.for all

With the antenna disconnected, connect a long wire (about 20 feet or so) to the stator of the Convertor section (likely the middle section) of the 3 gang tuning condenser. You should receive several stations with some normalcy. If hum or motor boating occurs, reinspect the AVC circuit. If good, touch the antenna to the stator of the RF section (Pin 4 of the antenna connector. Similar but better performance should occur.

RE: 52-942 - Ken Arroyo - 07-03-2025

Turns out the local oscillator is gone. Tried the test where you put another radio next to this one, etc. Not a peep. This thing must have been serviced before, as there are discrepancies between the schematics and notes I got from Nostalgia Air. For example, this should have a three-section electrolytic, but there were two caps, a double section and a single. None were the values in the schematic.
The power switch was bad too. I put in a jump and then a vintage line switch. I've been playing guacamole with this thing for a month.

RE: 52-942 - MrFixr55 - 07-03-2025

If the local oscillator is gone, dunno how you picked up a station. Pentagrid convertors are rather straightforward.

You may have to put the test radio (the good one) under the chassis of this radio near the local oscillator with the test radio dial set to about 1100KHz, then "sweep" tune this set, listening for squeals in either set. This radio has an RF stage which kinda shields the oscillator from emitting like a 5 tube set does.

I hear you regarding the frustration. I worked on a Philco 89 from the 7th ring of you know where, with a tetrode autodyne convertor stage for close to a year before I got it working.

RE: 52-942 - Ken Arroyo - 07-10-2025

More power to you if you have that kind of patience; I certainly don't. I didn't wait for the bulk trash pickup.