04-03-2021, 07:23 AM
From my point of view, we need to step back and check the power supply and associated voltages, or back to the basics. If you think of it in simple terms, a car won't start with a weak or dead battery. A radio will not work if its power supply is not behaving for some reason. Attached is the voltage chart for all to look at with us.
A few things come to mind based on comments made.
First, make sure that you know what parts of the circuit are AC volts, and what parts are DC Volts. I think you understand this already, so please don't take my comment the wrong way.
I suggest measuring the resistance between the chassis and the HV center tap. Id expect to see 128 ohms. Also using an ohm meter, measure resistance between HV center tap, the - terminals of C59A, C57, and the + of C59. they should all read 0 ohms or whatever you meter reads with its test leads shorted, usually a little more than 0 ohms because of lead resistance. Occasionally when old filter caps are removed from the circuit, mis-wiring occurs to the various leads that were connected to the capacitor terminals. Double check that nothing was missed. Also check the resistance across 59a to chassis, and 57 to chassis to make sure there are no shorts.
All ohm meter tests are done with no power applied. Resistance test without power can really find issues and keep caps from blowing and potential transformer damage.
It appears that all DC voltages are measured to chassis as well. The one exception is the first filter cap 59A which Philco gives you 2 voltages to check. One across the cap and one from + to Chassis. This reading shows that there is 15VDC difference between Chassis and 59A negative. The 15 VDC is what you should see across R58 and is the bias for the 6F6 tubes.
You mentioned that voltages around the rectifier tube are off. You must have approximately 5 volts AC across the filament pins, not pin to chassis. Also, per the attached chart, you should see 350 V AC from the center tap to each of the plate pins, or approximately 700 VAC across the plate pins. I suggest measuring the voltages at the rectifier tube socket. You should use caution in the socket area as its mounted on top of the power transformer. Quite often the old wiring/insulation under the socket degrade over time. This may not be happening, as it seems your power transformer is not overheating, but it is worth being aware of this.
Besides measuring the DC voltage across C59A (315VDC to chassis), there should be 265 VDC from C57 + to chassis. This calculates out to approximately 50 VDC across the field coil with a current of 108 Ma.
R58 should have 15 VDC across it with C59 + to chassis.
If the readings are very high, I'd would really look for mis-wiring, or simply a lead that was missed. I also see what look like cold solder joints. I suggest cleaning up the old solder from any of the terminals you worked on and flowing in fresh solder for a nice shiny connection.
Let us know what you find.
A few things come to mind based on comments made.
First, make sure that you know what parts of the circuit are AC volts, and what parts are DC Volts. I think you understand this already, so please don't take my comment the wrong way.
I suggest measuring the resistance between the chassis and the HV center tap. Id expect to see 128 ohms. Also using an ohm meter, measure resistance between HV center tap, the - terminals of C59A, C57, and the + of C59. they should all read 0 ohms or whatever you meter reads with its test leads shorted, usually a little more than 0 ohms because of lead resistance. Occasionally when old filter caps are removed from the circuit, mis-wiring occurs to the various leads that were connected to the capacitor terminals. Double check that nothing was missed. Also check the resistance across 59a to chassis, and 57 to chassis to make sure there are no shorts.
All ohm meter tests are done with no power applied. Resistance test without power can really find issues and keep caps from blowing and potential transformer damage.
It appears that all DC voltages are measured to chassis as well. The one exception is the first filter cap 59A which Philco gives you 2 voltages to check. One across the cap and one from + to Chassis. This reading shows that there is 15VDC difference between Chassis and 59A negative. The 15 VDC is what you should see across R58 and is the bias for the 6F6 tubes.
You mentioned that voltages around the rectifier tube are off. You must have approximately 5 volts AC across the filament pins, not pin to chassis. Also, per the attached chart, you should see 350 V AC from the center tap to each of the plate pins, or approximately 700 VAC across the plate pins. I suggest measuring the voltages at the rectifier tube socket. You should use caution in the socket area as its mounted on top of the power transformer. Quite often the old wiring/insulation under the socket degrade over time. This may not be happening, as it seems your power transformer is not overheating, but it is worth being aware of this.
Besides measuring the DC voltage across C59A (315VDC to chassis), there should be 265 VDC from C57 + to chassis. This calculates out to approximately 50 VDC across the field coil with a current of 108 Ma.
R58 should have 15 VDC across it with C59 + to chassis.
If the readings are very high, I'd would really look for mis-wiring, or simply a lead that was missed. I also see what look like cold solder joints. I suggest cleaning up the old solder from any of the terminals you worked on and flowing in fresh solder for a nice shiny connection.
Let us know what you find.
Tony
“People may not remember how fast you did a job, but they will remember how well you did it”
