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Philco Farm Radio 38 123 - Printable Version

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Philco Farm Radio 38 123 - RCFlyer - 02-21-2019

I've been working on a Philco 38 code 123 Radio.  I made the power supply from a kit purchased from AES.  All tubes have been checked and capacitors replaced. Radio doesn't make any sound just a faint popping noise when I wiggle the tubes.  Can someone instruct me how to align the radio, or other information I can use to troubleshoot the radio.  
Thanks

RE: Philco Farm Radio 38 123 - Nathan Slingerland - 02-21-2019

Basic alignment instructions can be found here:
http://www.silverslingshot.com/PDFFILES/aligningphilcoreceivers_1937.pdf

But if it's not really working at all I'd probably start by tracing through the schematic and parts info here:

http://www.nostalgiaair.org/Resources/231/M0013231.htm

Or here:

http://philcoradio.com/library/index.php/service-info/philco-wiring-diagrams-vol-1/

Perhaps use another AM radio to see if the local oscillator is running?

RE: Philco Farm Radio 38 123 - Radioroslyn - 02-21-2019

For starters I would measure the voltage @ pin 2 and then pin 5 of the 19 W/the meter - connected to the chassis. Should see abt 135vdc. Measure the dc voltage @ pin 2 of the 30 tube, should see abt 135vdc. Check dc voltage @ pins 3 and 4 to chassis of the 19 tube, should see -3v. And pin 3 of the 30 tube should be -7vdc. If any of these voltage are very low or nonexistence then check the resistance of the associated transformer. All winding should be <1000 ohms.
This is presuming that the power supply is working/ connected properly.
Happy hunting!

RE: Philco Farm Radio 38 123 - RCFlyer - 02-21-2019

Power supply is putting out the correct voltages  except for the 135 Volt  lug is producing 124 volts and the 67 1/2 volt lug is producing 64 volts.  I checked the voltages at #19 and #30 tubes. T he heater voltage is 2 volts. The plate voltages are a little lower.   The bias voltage -7 of the #30 tube changes when I turn the volume control.
I'm somewhat confused on the alignment procedure. 
Thanks for all the help.

RE: Philco Farm Radio 38 123 - Radioroslyn - 02-21-2019

>The heater voltage is 2 volts. The plate voltages are a little lower.

Confused. The plate voltage is lower that 2v??

>  The bias voltage -7 of the #30 tube changes when I turn the volume control.

The volume control in this set is connected to the input of the mixer and the -7v line goes the ground thru a resistor as the volume is adjusted. Most sets the volume control is connected to the det and 1st audio stage. .

>I'm somewhat confused on the alignment procedure.

Well let's start off easy. Set your generator for produce a modulated signal @ 460kc. Connect the hot lead to the grid cap of the 1A6. At this point you should the tone coming from the set. You may have to tune the generator a little to get the max signal. Tuning the dial on the radio will not effect this adjustment.  Adjust trimmers 16,18,19 and 21. This completes the IF alignment.

RE: Philco Farm Radio 38 123 - RCFlyer - 02-22-2019

I connected the RF Generator per the instruction above, no tone is generated through the speaker. Any  suggestions or information is greatly appreciated.  Thanks

RE: Philco Farm Radio 38 123 - 35Z5 - 02-23-2019

(02-21-2019, 06:27 PM)RCFlyer Wrote:  Power supply is putting out the correct voltages  except for the 135 Volt  lug is producing 124 volts and the 67 1/2 volt lug is producing 64 volts.  I checked the voltages at #19 and #30 tubes. T he heater voltage is 2 volts. The plate voltages are a little lower.   The bias voltage -7 of the #30 tube changes when I turn the volume control.
I'm somewhat confused on the alignment procedure. 
Thanks for all the help.

Trying to align a dead radio is not the way to troubleshoot, likely only create additional issues. Proper alignment relies on radio producing a signal that can be measured at speaker.

RE: Philco Farm Radio 38 123 - RCFlyer - 02-23-2019

Thanks for clarifying I have a dead radio. I'm taking it to the dumpster. Thanks again for all the help

RE: Philco Farm Radio 38 123 - Radioroslyn - 02-23-2019

If your generator has an audio output (some have a 400cy audio output) you can connect it to the grids (one at a time thru a cap) of the 30 and the 19 tubes to hear if it will pass any audio.

RE: Philco Farm Radio 38 123 - RCFlyer - 02-23-2019

Well I gave it another try.  I switched out #32 tubes and replaced a .01 mfd capacitor I missed under a part 27.  I was able to hear 460kc with the generator  lead attached to the cap  of A16 .  The noise  increase as I adjusted the variable caps.  Now I hear a faint radio station only when I touch the cap of one #32 tubes.  I turn the dial but the same station plays.

RE: Philco Farm Radio 38 123 - Stall-U-Rated - 02-23-2019

Sounds like youre getting some life from it, keep up the fight... Dont give up.. Icon_smile

Steve

RE: Philco Farm Radio 38 123 - Arran - 02-23-2019

When tubes have grid cap, those can become flaky in a battery set, the solder joints in particular, sometimes the cement holding them on also gives out. The grid cap leads also often had failing solder joints, as well as the wires breaking internally, it's worth checking first. The 1A6 and the two #32s all have grid caps, the #30s do not, nor does the #19.
Regards
Arran

RE: Philco Farm Radio 38 123 - RCFlyer - 02-24-2019

I checked the wires to the grid caps for continuity , they test fine.   I have an Eico 666 tube tester .  It doesn't list the 1A6 on the built in chart.   There's a socket it fits into, and a grid cap wire.
Is it possible to test the tube on this tester.   I can guess the filament voltage should be set at 2 volts.  I'm stumped on the rest.

RE: Philco Farm Radio 38 123 - Radioroslyn - 02-24-2019

http://bama.edebris.com/manuals/eico/666/charts-05

RE: Philco Farm Radio 38 123 - RCFlyer - 02-25-2019

Thankyou for the Tube tester charts.  It's incredible how many more tubes can be tested on the meter.   Well I did more testing and I think I'm narrowing the problem down
to the antenna transformer.  Schematic says 7.2 ohms from the wiper of the volume through the coil.  I'm reading 2.4 ohms .  Any suggestions.  Can I inject sound from another source 
like a CD player through a capacitor at a point after the oscillator to verify?