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Philco 46-480 Replacing Field Coil w/ Perm Mag (I know I know)
#9

Hi Retrorev,

Sounds like your wiring is correct. make some voltage readings. All of the Radio's current goes through that resistor. This is a somewhat strange setup in that the field coil was in the B Power Supply return. That wsa done years ago by RCA to keep the field coil voltage above (or below) chassis ground as low as possible. To troubleshoot:
- With all tubes in place, carefully check the voltage between the Audio Output transformer red wire B+ and Chassis Ground. DANGER!!! This is high voltage. Voltage should be around 250V. Check across the 100 0Ohm Resistor and note the voltage. - Check across C59 (Between Rectifier Cathode and center tap of HV Secondary). The sum of the B+ Voltage and the voltage across the resistor should equal the voltage across C59, which will likely be between 300 and 350 Volts DC.

If this is all good, inject an audio signal from a CD, MPE, etc. Headphone jack through a 47K Resistor between the junction of C47, r26, C42 and R20, and chassis ground. Clean audio should be heard from the speaker. If so, the power supply and Audio Section are good. troubleshoot the RF, IF and Detector section.

Hope this helps.

Best Regards,

John, MrFixr55

"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
RE: Philco 46-480 Replacing Field Coil w/ Perm Mag (I know I know) - by MrFixr55 - 09-13-2022, 03:09 PM



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