10-28-2012, 09:53 AM
I Thank you for the suggestion, I have it better but not perfect.
I am not an expert, I don't understand the terminology being put forward. I am coming from a background of computer science and working on old phones, which is vastly simpler that radios.
I have no electronics background, but have a healthy respect for electricity and alway try to be safe (Isolation Transformer, Variaac etc)
Some of the suggestions here, I simply don't understand what exactly you are suggestion. Perhaps that means I should be doing this type of work, but I really would like to learn more about working on these type of radios, just under a safe enviorment.
For example the following suggestions, I don't even know where to begin with regard to them
As for the bypass capacitors, yes they are usually paper caps, there is a large one that goes between the B- and the chassis, in Philco sets there is also a coil in series with it, if this is left out the set will howl and motorboat. There may also be a few others that run between various things and the B-, B- is what some call common negative.
Also be sure the built-in antanna loop is connected correctly AND that it has continuity. If there is an open loop, AVC voltage will not get to the front end tube and the gain will run wide open also causing the exact distortion you have. Also check all the components in the AVC buss as well as the 150K resistor at the loop.
[AVC is Automatic Volume Control ? I have no idea as to how to check components in the AVC buss and the 150K resistor at the loop. Is there a part of the schematic that shows AVC buss ??? Again, real new to this and the terminalogy, schematics, etc are killing me]
Those loop antennas have fairly thin wires and it isn't unusual for the wire at either end to break off on the secondary winding where it is soldered to the chassis or the antenna section of the tuning condenser. In fact on many of these late 40s Philcos the loop antenna is glued onto the inside perimeter of the cabinet, you really have no choice but to disconnect it to get the chassis out, and there are four wires coming off of it, two go to chassis ground (not B-), one goes to the tuning condenser, and one is the external antenna connection. If this is the case then they would have had to disconnect the loop antenna to remove the chassis in both sets, this my be why both appear to have the same problem.
[Yes, this has the loop glued into the inside of the case, and you do have to unsolder to get the chassis fully out. There are 4 wires coming off of it ???? I only see 2 ]
I'd also test for continuity of the IFT's, both pri and sec windings.
[what is continuity, what are the primary and secondary windings ?]
I really appreciate the help, I am trying to look up as much terminology as possible, but I am lost as to what some of these things are that you want me to check.
I am not an expert, I don't understand the terminology being put forward. I am coming from a background of computer science and working on old phones, which is vastly simpler that radios.
I have no electronics background, but have a healthy respect for electricity and alway try to be safe (Isolation Transformer, Variaac etc)
Some of the suggestions here, I simply don't understand what exactly you are suggestion. Perhaps that means I should be doing this type of work, but I really would like to learn more about working on these type of radios, just under a safe enviorment.
For example the following suggestions, I don't even know where to begin with regard to them
As for the bypass capacitors, yes they are usually paper caps, there is a large one that goes between the B- and the chassis, in Philco sets there is also a coil in series with it, if this is left out the set will howl and motorboat. There may also be a few others that run between various things and the B-, B- is what some call common negative.
Also be sure the built-in antanna loop is connected correctly AND that it has continuity. If there is an open loop, AVC voltage will not get to the front end tube and the gain will run wide open also causing the exact distortion you have. Also check all the components in the AVC buss as well as the 150K resistor at the loop.
[AVC is Automatic Volume Control ? I have no idea as to how to check components in the AVC buss and the 150K resistor at the loop. Is there a part of the schematic that shows AVC buss ??? Again, real new to this and the terminalogy, schematics, etc are killing me]
Those loop antennas have fairly thin wires and it isn't unusual for the wire at either end to break off on the secondary winding where it is soldered to the chassis or the antenna section of the tuning condenser. In fact on many of these late 40s Philcos the loop antenna is glued onto the inside perimeter of the cabinet, you really have no choice but to disconnect it to get the chassis out, and there are four wires coming off of it, two go to chassis ground (not B-), one goes to the tuning condenser, and one is the external antenna connection. If this is the case then they would have had to disconnect the loop antenna to remove the chassis in both sets, this my be why both appear to have the same problem.
[Yes, this has the loop glued into the inside of the case, and you do have to unsolder to get the chassis fully out. There are 4 wires coming off of it ???? I only see 2 ]
I'd also test for continuity of the IFT's, both pri and sec windings.
[what is continuity, what are the primary and secondary windings ?]
I really appreciate the help, I am trying to look up as much terminology as possible, but I am lost as to what some of these things are that you want me to check.
