Posts: 201
Threads: 26
Joined: Dec 2005
City: Morris Plains, NJ
I've got a box model 52. All of the caps have been changed, many of the resistors (they seem to go bad rapidly now that it's been fired up).
Philco's have been on my repair bench for 40 years but this model is the worst. Low sensitivity and volume just plague this radio. It's one of the earliest Philco superhets and they sure didn't use many parts in it. Does anyone else share these opinions on the 52?
Pete AI2V
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
It is an early TRF and needs a good ground and an external antenna of at least 25-30 ft. to perform well. Also check, you may have an open coil winding(s) in RF coils 2, 5 and/or 7. Very common. Also be sure the dual "volume" pot sections are in spec., part no. 1.
Posts: 201
Threads: 26
Joined: Dec 2005
City: Morris Plains, NJ
My schematic for the 52 has a 24 tube as the input mixer/oscillator, a 35 as the IF (175KC), and a 24 as the AM detector. The Model 50 schematic appears at the top of the page for the 52 data sheet- perhaps that's what you saw.
Still I'll be checking the continuity of the coils. My input signals come from an HP 8640 Sig Gen or a 70' antenna- that's why I think something is wacky. I'll report back what I find.
Pete AI2V
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
Yes, sorry.
Was rushing during lunch-break at my desk at work....
"...sometimes the Bear bites you".
You still could have an open coil somewhere or the Sensitivity control (No.9) is not set right, according to the alignment procedure.
If turned down, it reduces the IF gain, if set to high, the IF can break into oscillation and cause signal blocking or squealing. The IF stage sensitivity control is actually a regeneration control to make the IF as high a gain as possible without breaking into oscillation.
Posts: 201
Threads: 26
Joined: Dec 2005
City: Morris Plains, NJ
Strange circuit- especially when someone in the past miswires it.
The volume pot not only controls the input signal but also some of the cathode biasing- turns out that the pot was missing it's center tap ground.
It's still not the best radio, but for a cheap 1932 superhet it's OK. Most likely I'll be eBay'ing it soon since I'm running out of room with all these big models in the way: 116B's, 640, 645, 650, 91, 70, 118, .........
Pete AI2V
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