The Fine Things are Always Hand Made
9 knob BOL Restoration
Hello All,
I’m finally getting around to starting the resto/repair process on my 9-knob, AM-only BOL Philharmonic. I’ve done this many times on ordinary radios, but for this particular set is there a tried-and-true process to power up and check things as I go? Looks like the amp/PS has had some work done to it at some point in the past already.
Thanks, Steve
Replies to This Discussion
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Permalink Reply by Norman S Braithwaite
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Make sure to tighten the rotors on the variable selectivity trimmers. The rotors are fastened to the shaft using set screws through pot metal collars. Over time the pot metal collars expand causing the set screw to become loose and allow corrosion and resistance between the set screw and the shaft. In the worst cases, the rotors can become completely loose allowing the rotor to spin freely on the shaft. Also, be aware that there are four wax-paper capacitor inside the base choke shield and two inside the tuning capacitor shield that will need to be replaced.
Norman
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Permalink Reply by Stephen Scheel
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Thanks Norman. i'll remedy that stuff after i give the PS a once over.
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Permalink Reply by David C. Poland
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The "bass choke shield"assembly is the topside chrome plated box (left rear) between the pair of 3rd audio 6J5's and the pair of Volume Expander 6L7's. Unsolder the 4 wires (making careful notes). Failure to replyace the caps inside risks damage to the bass control potentiometer. Allows better access to clean that chrome area, and access to replace the shock mount grommets for those 6L7s.
Also, expect to find a soldered box with seven .5 MFD (not .05) caps (approximately below the Expander tubes). This is part 1321 on page 14-60 in Riders (aka C51 on the diagram). I dismount that box to open it up, after cutting the 7 wires near the box. I re-stuff that box with modern 630 volt caps and connect to the 7 cut wires (with heat shrink spaghetti), rather than trying to trace and unsolder those long leads. The box is ground for the these caps.
Those underside diode assembles in metal boxes also have a protruding cap to replace. Tedious but important.
By the time you are done, you will be well acquainted with the Philharmonic. Do read through the owners manual too. Have Fun.
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Excellent! Thank You David.
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Bass choke assembly consists of two chokes and 4 caps, it is a resonator to increase bass response.
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oh wow.. i had no idea. this is going to be fun.
David C. Poland said:Bass choke assembly consists of two chokes and 4 caps, it is a resonator to increase bass response.
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