I just recapped a Model 60. Initially I recapped the filters (electrolytics and the filter block caps). I tried the radio and it worked for a few seconds, then dead.

I continued to recapp (leaving in the blocks, but bridging across them after disconnecting the internal wires from the lugs). Same result.

I then changed the tone caps and did not realize there were two in there (a .01mf and a .015 which is switched on oand off with the control), so I only changed only the .015 mf tone cap. After powering up, I would get a loud squeal when switching off the .015 cap. With it switched on, I get just modulation hum.

I caught my error and added the .01 cap back into the tone circuit. After powering up the radio with all caps replaced and the tone caps right (.01 & .015), I now get a loud squeal when switching off the .015mf tone cap, using only the .01mf cap as a bypass, just like before, except I didnt have the .01 in the circuit yet. I do have good solder joints.

I also checked voltages and all tubes are a little low, with one very low. The 6A7 is 232v, should be 250v; 78 is 232v, should be 250v; 75 is 93v, should be 170v; 42 is 204v, should be 254v and the 80 is 349v both plates.

I will recheck solder joints, but what would make the 75 so low and the others a little low? I am not sure how to troubleshoot.

This is a late Model 60, made in 1936 as far as I can tell.

Thanks in advance for your help.

Steve

My Philco 60 squealed, too. Not sure exactly what fixed it, but here is the start of the link whcih is quite long, but may be useful to you. Many voltage readings and help from Edd, Thomas Dermody and Radiodoc.

At any rate, mine plays like a champion now.

http://www.nostalgiaair.org/forums/Messages/864/M0057864.htm

Good luck,
TF

:I just recapped a Model 60. Initially I recapped the filters (electrolytics and the filter block caps). I tried the radio and it worked for a few seconds, then dead.
:
:I continued to recapp (leaving in the blocks, but bridging across them after disconnecting the internal wires from the lugs). Same result.
:
:I then changed the tone caps and did not realize there were two in there (a .01mf and a .015 which is switched on oand off with the control), so I only changed only the .015 mf tone cap. After powering up, I would get a loud squeal when switching off the .015 cap. With it switched on, I get just modulation hum.
:
:I caught my error and added the .01 cap back into the tone circuit. After powering up the radio with all caps replaced and the tone caps right (.01 & .015), I now get a loud squeal when switching off the .015mf tone cap, using only the .01mf cap as a bypass, just like before, except I didnt have the .01 in the circuit yet. I do have good solder joints.
:
:I also checked voltages and all tubes are a little low, with one very low. The 6A7 is 232v, should be 250v; 78 is 232v, should be 250v; 75 is 93v, should be 170v; 42 is 204v, should be 254v and the 80 is 349v both plates.
:
:I will recheck solder joints, but what would make the 75 so low and the others a little low? I am not sure how to troubleshoot.
:
:This is a late Model 60, made in 1936 as far as I can tell.
:
:Thanks in advance for your help.
:
:Steve
:Steve, Make sure the grid wire on the 75 tube is routed inside the tube shield. That will cause a squeal as you describe. As for the low voltage, check the bias on the 42 tube. Steve

::I just recapped a Model 60. Initially I recapped the filters (electrolytics and the filter block caps). I tried the radio and it worked for a few seconds, then dead.
::
::I continued to recapp (leaving in the blocks, but bridging across them after disconnecting the internal wires from the lugs). Same result.
::
::I then changed the tone caps and did not realize there were two in there (a .01mf and a .015 which is switched on oand off with the control), so I only changed only the .015 mf tone cap. After powering up, I would get a loud squeal when switching off the .015 cap. With it switched on, I get just modulation hum.
::
::I caught my error and added the .01 cap back into the tone circuit. After powering up the radio with all caps replaced and the tone caps right (.01 & .015), I now get a loud squeal when switching off the .015mf tone cap, using only the .01mf cap as a bypass, just like before, except I didnt have the .01 in the circuit yet. I do have good solder joints.
::
::I also checked voltages and all tubes are a little low, with one very low. The 6A7 is 232v, should be 250v; 78 is 232v, should be 250v; 75 is 93v, should be 170v; 42 is 204v, should be 254v and the 80 is 349v both plates.
::
::I will recheck solder joints, but what would make the 75 so low and the others a little low? I am not sure how to troubleshoot.
::
::This is a late Model 60, made in 1936 as far as I can tell.
::
::Thanks in advance for your help.
::
::Steve
::Steve, Make sure the grid wire on the 75 tube is routed inside the tube shield. That will cause a squeal as you describe. As for the low voltage, check the bias on the 42 tube. Steve
:

I know that my 60 will work well without the shields, but works better with them. You must use a 78 and not a 6D6, because 78 has built in shielding. Keep speaker wiring away from tubes and the antenna. Be sure that you are also checking and/or replacing the caps in the bakelite blocks, and not just those in the tin filter cap box.

If you get a squeel with the tone cap out of the circuit, but none when it is in the circuit, then something is feeding back from the output to some other point in the radio at a frequency that is supressed by the tone cap when it is put into the circuit. Be especially sure that you wired the filter cap box correctly, because there are a lot of caps in that box that stabilize various points in the radio, and also tie to at least one common point. If those points are not stabilized properly, and/or if the caps' common point isn't connected to the chassis properly, feedback can actually occur from one point in the radio to another through the filter caps within that box.

T.

Actually, regarding hum and squeal, the Philco 60 shouldn't hum at all. At least mine doesn't. Filtering is so good that there is virtually no hum. Considering that, take a look at your filter caps. In my radio they are held in place with a clamp that presses against both of them and screws into a portion of the chassis that is stamped so that it faces upward. Insulating the filter caps from the chassis are cardboard tubes, since the filter caps aren't supposed to connect to the chassis, but rather to the transformer center tap. To connect them to the transformer center tap, small straps of metal are held between the filter caps and their respective cardboard sleeves via the pressure of the clamp. A wire is soldered to these metal strips, and also to the transformer center tap wiring. Should you have forgotten to insert the metal strips so that they make contact with the filter caps (if you re-stuffed the filter caps), the filters would in fact not have a negative connection. This would allow for hum as well as feedback through the B+ wiring from the output tube.

If, instead of re-stuffing the original filter caps, you wired in replacements under the chassis, be sure that their negatives are connected to the transformer center tap and not to some other point in the radio.

T.

Not connecting the electrolytic filter caps correctly would also cause a reduction in B voltage.

T.

:Not connecting the electrolytic filter caps correctly would also cause a reduction in B voltage.
:
:T.
:

You'd have to say what the 70K resistor connects to on the 42 for me to know what's going on.

If you used filter capacitors that are significantly larger than the originals, then this might be the cause of increased voltages, though it might also be due to whatever is not functioning in the radio. A broken coil or otherwise dead tube circuit can cause voltages to go up.

T.

The 70k is actually wired correctly. I took a long time to trace everything and it seems in the right place. My filter caps are new and the same size as the schematic (10mf each).

I started to use my ohm meter to check the coils. I believe I have an open in the smaller of the two oscillator coils.

There seems to be an open between pin 4 of the 6A7 and one side of the .00011mf cap (Part 13 in the schematic) that is connected to the other side of the coil in question. I believe these are the correct test points for an ohm meter check.

Is there another way to confirm this coil is open (test signal or some other way) before I go through the trouble of removing it to rewind in the event I am wrong with my diagnosis?

What size wire should I use if it is bad?

Thanks Thomas,

Steve

:You'd have to say what the 70K resistor connects to on the 42 for me to know what's going on.
:
:If you used filter capacitors that are significantly larger than the originals, then this might be the cause of increased voltages, though it might also be due to whatever is not functioning in the radio. A broken coil or otherwise dead tube circuit can cause voltages to go up.
:
:T.
:

That is correct. Another test is to see if there's B+ on pin 4. If none, then you can be pretty sure that the coil is open.

With the oscillator not working, voltages may be higher, but probably not by much. Mine was corroded through, and I don't recall what size wire I used. I believe that I removed it from a small output transformer primary. Something in the neighborhood of 40 gauge would be close enough. It's very thin. Count the turns as you remove the original coil, and wind the new coil in the same direction. If the oscillator fails to oscillate, you can reverse the connections later, but hopefully you will have wound it correctly to begin with. Try to be neat, but it isn't extremely critical.

T.

I got home early today and started to look into the oscillator coil.

After removing it and rechecking the continuity, the smaller coil was open. I used the wire from an AA5 transformer that I replaced in another radio which had an open secondary.

I glued the wire to the form after I wound it and put everything back together.

It worked! Now I need to find the square tube shields for the 75 and 78 that are missing. I am usung makeshift ones now and have noisy reception. Time for a swap meet for that. Thanks for all your help.

Steve

:That is correct. Another test is to see if there's B+ on pin 4. If none, then you can be pretty sure that the coil is open.
:
:With the oscillator not working, voltages may be higher, but probably not by much. Mine was corroded through, and I don't recall what size wire I used. I believe that I removed it from a small output transformer primary. Something in the neighborhood of 40 gauge would be close enough. It's very thin. Count the turns as you remove the original coil, and wind the new coil in the same direction. If the oscillator fails to oscillate, you can reverse the connections later, but hopefully you will have wound it correctly to begin with. Try to be neat, but it isn't extremely critical.
:
:T.
:

Lack of shields won't cause noisy reception. It'll cause squealing and howling, sometimes severe and usually mild--when dealing with this radio. The audio might take on a hollow sound due to small feedback.

If you have noisy reception, consider erecting a long outdoor antenna (in a straight line--no bends).

T.

You're right. I wasn't clear. It is squealing that I meant. But its better with the makeshift shields than without.

:Lack of shields won't cause noisy reception. It'll cause squealing and howling, sometimes severe and usually mild--when dealing with this radio. The audio might take on a hollow sound due to small feedback.
:
:If you have noisy reception, consider erecting a long outdoor antenna (in a straight line--no bends).
:
:T.
:

The shields show up on eBay from time to time. Be sure that they were either definitely pulled from a 60, or that they have the same measurements, before you bid on shields that might not fit your radio.

T.