This radio is just dead. Tubes check good and electrolytic caps changed. Still just dead except for some static and I can't tell what band it's on as none of the lights lite. There is one electrolytic cap that has two 40ufd sections wired but no ground connection. Wired this way is it a nonpolarized electrolytic?...and what is it used for. I don't see it on the schematic. I think it has something to do with the motor they are using to change bands.

Hi John
I see two 40uF capacitors, C72 & C75. They have their commons grounded. Not having the common connected to anything cannot be right.
I don't think that is your problem with the radio being dead, although you need to fix that. You describe what sounds like a problem in the IF or RF section.
This radio looks like a hand full.

Best Regards,

Bill

:This radio is just dead. Tubes check good and electrolytic caps changed. Still just dead except for some static and I can't tell what band it's on as none of the lights lite. There is one electrolytic cap that has two 40ufd sections wired but no ground connection. Wired this way is it a nonpolarized electrolytic?...and what is it used for. I don't see it on the schematic. I think it has something to do with the motor they are using to change bands.
:

From reading the Riders comments about tuning in FM, it sounds like Bill is right - maybe even two hands full.

I would start with some voltage checks and then signal injection, working from the output until I got to the bandswitch. Then if the trouble is in the bandswitch I would probably get my big sledge hammer out. :>)

Thanks Bill, I see C72 and C75 on the dia. and have changed them. The 40's I was refering to are both in a single can with a black cardboard jacket so insulated that way from ground and there is no connection to ground of the metal part of the can. The leads from each 40 section of the can go to the first section of the band switch and I think from the dia. this cap might be C109. Anyway none of the band switch lites come on and I can't switch bands. Work continues today. I'll keep you posted. John

:Hi John
: I see two 40uF capacitors, C72 & C75. They have their commons grounded. Not having the common connected to anything cannot be right.
: I don't think that is your problem with the radio being dead, although you need to fix that. You describe what sounds like a problem in the IF or RF section.
: This radio looks like a hand full.
:
:
:Best Regards,
:
:Bill
:
::This radio is just dead. Tubes check good and electrolytic caps changed. Still just dead except for some static and I can't tell what band it's on as none of the lights lite. There is one electrolytic cap that has two 40ufd sections wired but no ground connection. Wired this way is it a nonpolarized electrolytic?...and what is it used for. I don't see it on the schematic. I think it has something to do with the motor they are using to change bands.
::
:
:

C109 is indeed a motor start/run capacitor (phase shifter), and its wires can be easily confirmed, since as shown in the schematic, two of the motor leads connect directly to the same switch terminals as the capacitor, so it should be an easy task to trace the wires from the capacitor to the switch and then to the motor.

A non-polarized unit should be used only, and it is correct that the unit found in the set not be grounded, as it should not be grounded. The two electrolytics back-to-back do form a non-polarized unit of about 20-24 MFD.

This capacitor is unlikely to be the cause of your troubles.

Though this set may seem daunting, troubleshooting is still straightforward. If it is dead on all settings, then start looking for something like an open resistor.

Before doing anything, if you are going to make use of the original electrolytics, be sure that they have proper capacitance and minimal leakage. Allow them to reform if necessary. Then go from there, checking voltages at the various tube sockets for the various bands. If dead on only one setting, look for the above, but also a dead oscillator or open coil, or dirty switch.

I worked on a set like this for a friend, which only required new audio interstage caps and one new electrolytic, but otherwise performed admirably on the rest of its original components. It had a fuse, so I was not too worried about shorts. Today I probably would have replaced more than I did, but it still worked well. It is wise to replace all paper caps unless in low voltage low impedance situations. The speaker had a leather surround and an aluminum voice coil, which excellent sound reproduction on FM with the Stromberg Carlson labyrinth.

T.

Yes, I thought that C109 was a non polarized start cap for the motor which doesn't run. Checked the values of the two 40's in the can and one was 35ufd and the other one was 70nfd so replaced the one side with a 33 ufd and so now have about 17ufd and the motor still won't run. How critical is that 20-24ufd they call for?? I oiled the motor and seems to be pretty free but won't run and there is quite a spark at the switch when activated. Turning the motor by hand to get to the AM band I can only get one real strong local station and volume is very low. Not sure why yet!

:C109 is indeed a motor start/run capacitor (phase shifter), and its wires can be easily confirmed, since as shown in the schematic, two of the motor leads connect directly to the same switch terminals as the capacitor, so it should be an easy task to trace the wires from the capacitor to the switch and then to the motor.
:
:A non-polarized unit should be used only, and it is correct that the unit found in the set not be grounded, as it should not be grounded. The two electrolytics back-to-back do form a non-polarized unit of about 20-24 MFD.
:
:This capacitor is unlikely to be the cause of your troubles.
:
:Though this set may seem daunting, troubleshooting is still straightforward. If it is dead on all settings, then start looking for something like an open resistor.
:
:Before doing anything, if you are going to make use of the original electrolytics, be sure that they have proper capacitance and minimal leakage. Allow them to reform if necessary. Then go from there, checking voltages at the various tube sockets for the various bands. If dead on only one setting, look for the above, but also a dead oscillator or open coil, or dirty switch.
:
:I worked on a set like this for a friend, which only required new audio interstage caps and one new electrolytic, but otherwise performed admirably on the rest of its original components. It had a fuse, so I was not too worried about shorts. Today I probably would have replaced more than I did, but it still worked well. It is wise to replace all paper caps unless in low voltage low impedance situations. The speaker had a leather surround and an aluminum voice coil, which excellent sound reproduction on FM with the Stromberg Carlson labyrinth.
:
:T.
:

If you can get one AM station, that's great. It's alive! Many of the major components are ok.

If you haven't done so, loosen the bandswitch motor mount and see if it will run disengaged. There are bushings in the bandswitch that will need a shot of contact cleaner.

Clean tube sockets and the volume pot. A corroded volume control will sometimes stop a good radio from playing at all.

Hi John,
I noticed on the schematic that some of these had thermostats in the motors. The first check on the motor is continuity.

Best Regards,

Bill Grimm