Since I had to wait for some parts I ended up having to wait until they came in to install the last three capacitors.
I decided rather than re-stuff the big can capacitors I would just clip the leads and wire around them leaving the dead cans in place for cosmetic reasons.
There was one big can capacitor missing though. The large filter capacitor next to the transformer had been replaced with a big orange Sprague Atom.
I couldn't find any "new" post-type multi-section capacitors, though I did find some "New Old Stock" (NOS) for a sky high price. The problem with NOS capacitors though is that they are still "OLD", just not "used", so that means they can still be just as bad as the ones your replacing, so I don't trust NOS electrolytic capacitors and in my personal opinion, it is dangerous to do so (especially if they are to be used as filter capacitors).
Instead I ordered a new Mallory multi-section "twist loc" type, but this proved problematic too. Since the hole was drilled for a post-type can capacitor, there was nothing to mount the new capacitor to AND this capacitor was NOT grounded so some way had to be found to electrically isolate the capacitor and the clamp from the chassis ground.
I remember taking an old capacitor out of a radio many years ago that had a rubber "boot" wrapped around the bottom. Now I don't know if they still make these boots or not, but it's easy enough to make. All you need is a strip of rubber... like from an inner tube perhaps?
So I took a bit of cheap bicycle inner tube and cut a small section out of it. I then cut that section LENGTHWISE (down the middle) and opened it up flat (since the tube was too small to simply slip over the bottom of the can). I then wrapped the rubber around the the body of the capacitor and mounted the clip.
I did have to do a bit of drilling into the chassis to get the screws to fit through properly and once it was mounted I had to be sure that the negative lug of the capacitor did not accidentally touch the chassis, but other than that it fit in quite smoothly.
The Speaker
At some point in the life of this poor radio someone switched out the original speaker for a more modern Zenith speaker with a permanent magnet. It had a good audio output transformer but no field coil. Since the field coil is part of the B+ circuit, I was advised to match the impedance of the original field coil with an inductive (or "Wire Wound") resistor. The original value was 1280 ohms, but since no-one makes exactly a 1280 ohm wirewound, I soldered a 1K and a 250 ohm together in series to approximate the 1280 ohm field coil. (I'm only about 3o ohms short, but I believe that's close enough).
A note about soldering these old speaker connections. These connectors solder up just like the PL-259 (the Amateur Radio Operators best fiend LOL!) or a copper water pipe. You want that "thermal wicking" action.
First off, forget conventional soldering irons and techniques and think more of plumbing than electronics. For this job your going to need some serious HEAT! Grab the 100 watt soldering gun for this one.
When you heat the connector, you must heat it from about HALFWAY down the shaft or lower. When the shaft is hot enough to melt the solder, feed the solder down into the center of the shaft until the rosin bubbles to the top (once this happens remove both the heat and the solder immediately). As the shank cools it will suck the solder down into the shaft of the pin and make a solid electrical connection.
To finish it all off, I covered the end of the resistors, where I soldered the two leads of the resistors together, with a bit of heat shrink tubing.
~~~~~~~~~ IT LIVES!!! ~~~~~~~~~
At long last, the time has come to double check the connections and plug it in to the dim bulb tester.
A flick of the power switch and the bulb glowed a beautiful pumpkin orange! (meaning no shorts in the transformer)
A twist of the tuning dial and a rich golden voice came booming through clear as a bell. No Silver Mica migration, no static or interference of any kind! Just clean rich audio.
I find it quite sad indeed that "talk radio" and "sports radio" is the only garbage we're left with in our area these days.
Now we need to check the tube voltages to be sure they're correct and that everything electrical is running smoothly, then we'll check to see if it's in alignment or how badly it's out of alignment if at all, then, on to restoring that cabinet.
But that, as they say, is another day.
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