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I had ohmed out all of the transformer windings so figured it was going to be OK. I brought it up slowly on the Voltac and when I got to 90 VAC the speaker started to crackle. Then it played at line voltage. There were stations on broadcast, and a few squeals on short-wave, this in the middle of the day. But there was considerable hum. The old bias cell was dead and tested about open. It's in the grid circuit of the 6SQ7 first audio so the grid was sort of open and picking up lots of hum. Just putting my finger close to the grid wiring increased it. Bridging the cell made it play without hum. I tried various experiments with resistors and caps and finally decided to leave the cell in but disconnected for looks, and replace it electrically with a cap. The set works fine and strong that way. Apparently thoughts and methods of providing bias changed over the years.
All controls were cleaned and lubed. The tuning capacitor was especially crackly: I blew it out with computer keyboard duster "air" and CRC Electronic Cleaner and then washed out the old grease from the ball bearings, replacing it with white grease. The bandswitch and toneswitch ball bearings and pawls got a little white grease, too. A little WD-40 went on the other bearings.
I checked voltage on the downstream side of the CL-90 inrush current limiter at turn-on, with the set plugged into line voltage. Almost immediately the voltmeter reads 60 VAC; then it slowly climbs over the next 30 seconds to just below line voltage. The slow start and the slightly less voltage supplied is good for the old gal. The CL-90 gets hot during operation so it's dropping a couple of volts. The power transformer is loafing along, hardly gets warm at all after a long time on.
The speaker voice coil was not rubbing, but doing the classic test -- hold the speaker near your ear and strike the back of the field pot with the heel of your other hand -- there was a buzz. This was traced to almost imperceptible tears in the corrugated surround. It looked as if a fine razor blade had made cuts in it, but was just due to paper deterioration. I thinned some fabric glue with water and painted the whole cone with it, with an extra coat around the surround. This strengthened it and resolved the problem. The fabric glue remains flexible so is ideal on the surround.
I tried the set on 20 ft. of wire across my garage ceiling, not even on my outdoor high long wire, and got lots of shortwave in the middle of the day, with W W V booming in and thumping its thumps on that heavy speaker. After that I touched up the IF alignment and that of all three bands, and adjusted the preset buttons to local and regional stations.
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Reece
Perfection is hard to reach with a screwdriver.
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