Grab a signal tracer or frequency generator (set up to the IF frequency), and start from the audio output back one stage at a time until you cannot hear the signal out of the speaker (I connect to the grid of each tube ). Hope this will help.
Sounds like I’m going to have to do that. I’ll put those on my Kutztown wishlist along with another Philco 1227 chassis. Maybe I’ll get lucky and figure out the radio’s problem. This is a real challenge. Steve
Speakers of that era use B+ CURRENT in place of a Permanent Magnet (they were weak back then). It also acts as a filter CHOKE. Try a modern speaker on the terminals output transformer terminals. (the 'choke' or substitute power resister must be in place.)
Thank you for that idea. I’ll keep this in mind for other radios that may come my way. The speaker I have works. I hooked it up to my ‘48 Philco and it sounds great. The problem, I think, is the lack of power or a signal getting to the speaker. I’m going to test all the plate and grid voltages next. But thank you again for your idea. Steve
Colors of the wires going to the speaker connector do not match up well to what was in there originally. If the orange is the original it's voltage shoulg be 290 VDC. There was a split to each control grid where that went to each 6K6 at pin 4. Now the red should not be a high negative voltage. In fact if the red goes to the plate of one of the 6K6 tubes (pin 3) it should be 280 Volts as well as the white going to the plate of the other 6K6. The green might be the wire going to a 68 Ohm resistor that then goes to one side of the volume control. I'm more concerned about the orange wire which is B+. It should only be 300 Volts or less not 468 Volts. The 6J5 Phase Inverter plate voltage ( pin 3) should be about 200 Volts and it's cathode at pin 8 should be less than 80 Volts. Also look at 7X7 tube pin 2 should be only 127 Volts and pin 3 a negative 0.5 volts. All the readings you get are DC only with no station tuned in to get a measurement .
Thank you for all the information. I will check these out again. I’m going to check the voltages to all the tubes first. Then go backwards from each speaker connector wire to the tube to the tube it’s connected to. Then still backwards from there. Maybe that will lead to the problem. I hope. Steve
What are you measuring the voltages with? A DMM used on high impedance valve circuits will give readings which while accurate will not match the service manual readings which were taken with an analogue meter. A good service manual should state what meter is to be used and on what range, you can shunt a DMM with a resistor to match the intended meter resistance.
Yes I use a digital multimeter. When this was made everything was analog. If the values are a little off, high or low, I’ll let it pass. Some are off just a few volts. Some readings are way off…then I look for a problem. Steve
@@My1925World They could be way off. The intended meter could be something like 5 k ohms per volt whereas even a cheap DMM is usually 11 M ohms or more. In a circuit where resistors are in the 100 k range the effect is very significant.
@@NiallWardropI’ll have to check what the repair literature said they tested with. An analog meter may be on the wishlist. Thank you for telling me this…could make a huge difference. Steve
@@My1925World It's been a while but I think the way it works is for example if the data says measure with a meter of 10 k ohms per volt sensitivity on the 3 volt range then the meter resistance will be 3 x 10k = 30k so if you put a 30k resistor across the input to a DMM it will be about right. If the circuit is very sensitive the data will say to use a Vacuum Tube Voltmeter (VTVM) which is the vintage equivalent of a DMM so the readings will be right without a shunt resistor.
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Grab a signal tracer or frequency generator (set up to the IF frequency), and start from the audio output back one stage at a time until you cannot hear the signal out of the speaker (I connect to the grid of each tube ). Hope this will help.
Sounds like I’m going to have to do that. I’ll put those on my Kutztown wishlist along with another Philco 1227 chassis. Maybe I’ll get lucky and figure out the radio’s problem. This is a real challenge.
Steve
Speakers of that era use B+ CURRENT in place of a Permanent Magnet (they were weak back then). It also acts as a filter CHOKE. Try a modern speaker on the terminals output transformer terminals. (the 'choke' or substitute power resister must be in place.)
Thank you for that idea. I’ll keep this in mind for other radios that may come my way. The speaker I have works. I hooked it up to my ‘48 Philco and it sounds great. The problem, I think, is the lack of power or a signal getting to the speaker. I’m going to test all the plate and grid voltages next. But thank you again for your idea.
Steve
Colors of the wires going to the speaker connector do not match up well to what was in there originally. If the orange is the
original it's voltage shoulg be 290 VDC. There was a split to each control grid where that went to each 6K6 at pin 4. Now
the red should not be a high negative voltage. In fact if the red goes to the plate of one of the 6K6 tubes (pin 3) it should
be 280 Volts as well as the white going to the plate of the other 6K6. The green might be the wire going to a 68 Ohm
resistor that then goes to one side of the volume control. I'm more concerned about the orange wire which is B+. It
should only be 300 Volts or less not 468 Volts. The 6J5 Phase Inverter plate voltage ( pin 3) should be about 200 Volts
and it's cathode at pin 8 should be less than 80 Volts. Also look at 7X7 tube pin 2 should be only 127 Volts and pin 3 a
negative 0.5 volts. All the readings you get are DC only with no station tuned in to get a measurement .
Thank you for all the information. I will check these out again. I’m going to check the voltages to all the tubes first. Then go backwards from each speaker connector wire to the tube to the tube it’s connected to. Then still backwards from there. Maybe that will lead to the problem. I hope.
Steve
What are you measuring the voltages with? A DMM used on high impedance valve circuits will give readings which while accurate will not match the service manual readings which were taken with an analogue meter. A good service manual should state what meter is to be used and on what range, you can shunt a DMM with a resistor to match the intended meter resistance.
Yes I use a digital multimeter. When this was made everything was analog. If the values are a little off, high or low, I’ll let it pass. Some are off just a few volts. Some readings are way off…then I look for a problem.
Steve
@@My1925World They could be way off. The intended meter could be something like 5 k ohms per volt whereas even a cheap DMM is usually 11 M ohms or more. In a circuit where resistors are in the 100 k range the effect is very significant.
@@NiallWardropI’ll have to check what the repair literature said they tested with. An analog meter may be on the wishlist. Thank you for telling me this…could make a huge difference.
Steve
@@My1925World It's been a while but I think the way it works is for example if the data says measure with a meter of 10 k ohms per volt sensitivity on the 3 volt range then the meter resistance will be 3 x 10k = 30k so if you put a 30k resistor across the input to a DMM it will be about right. If the circuit is very sensitive the data will say to use a Vacuum Tube Voltmeter (VTVM) which is the vintage equivalent of a DMM so the readings will be right without a shunt resistor.
@@NiallWardropI’ll have to look that up and give the resistor fix a try. Thank you.
Steve