Filter Caps Ordered

Last item does not count, the connector is for my signal generator

Tubes Ordered

New tuning Clutch and Tuning U-Joint

Today I replaced the tuning clutch disc and U-joint disc. Both are made out of rubber that has dried up and started cracking. These will just need to be replaced later so it is best to replace them now.

 Removing tuner section. Front of radio just unbolts from the chassis and the eight connecting wires were unsoldered.

Tuner section removed

 

 Old tuning clutch. This clutch is used to disengage the tuning knob when station selector buttons are pushed. Rubber clutch is all dried out and cracked.

 Tuning components removed

 Old U-joint made from cloth reinforced rubber cracked in several places

 Note clutch rubber falling out of assembly

 Outer clutch disc crimped is crimped onto the shaft

 Filing off the crimp to get the clutch disc off

 I drilled and tapped the shaft end for a 4-40 SS screw

 

 Test fitting the clutch disc mounted with screw

 Spraying neoprene rubber clutch disc pads and clutch discs with contact cement

 Applied the rubber pads to the clutch discs and pressing until dry

 Old U-joint

 Old U-joint with rivets drilled off

 New neoprene U-joint disc

New U-joint assembled

 

 Tuning components installed and tuner section installed in radio

Installed U-joint

YAY!!

 I temorarily added a filter capacitor to reduce hum from my battery charger. Those higher wattage resistors are replacing a trimmer potentiometer.

Here is the old trimmer potentiometer that adjust the output transistor bias current. It is dead. Looked on Digikey, apparently this type is no longer being made. I can just pick and choose fixed resistors to get the bias correct or find another potentiometer that would work. This is a 125 Ohm potentiometer.

Control shaft detail

Found a pot at Newark for $11.14. Not exact fit but a better part and it will do the job well:

Problem #1

Got the schematic today from Brian and started a little debug. I knew that the output transistor and the 12K5 tube driving the transistor was working so I started checking voltages at the detector stage. All looked good at the detector so I went to the last IF amplifier stage and found that the plate voltage was zero. Checked the voltage on the other end of the IF transformer primary winding and found 12 volts. It appeared that the primary winding was open so I removed the IF transformer and did find a broken wire. Not sure what happened to the transformer but it looks like the wire was eaten. There was about 1" missing. So I installed a jumper wire and found that the "sort of plastic" base was crumbling. I pulled out the epoxy and patched it up. Tomorrow I'll put the transformer guts back in it's case and reinstall it. Not the best of situations but that is sometimes the way it goes. The likeliness of finding a good replacement transformer is somewhere between nil and zero...

Here is the bottom of the chassis showing the bottom of the transformer

 Transformer removed

 Transformer guts removed from it's case

 Guts with the added jumper wire and a bunch of epoxy slathered all over the base.

Schematic

Some Cleaning

 Bezel straightened and cleaned up with the knob echelons

Top and bottom cover cleaned up. I went over these lightly with a wire wheel so as to not remove to much of the plating but remove the rust. Then a coat of paste wax.