Philco 38-7 Console Radio Repair Journal
by Chad Hauris, Retro
Electronics and Audio Lab, Midland, TX. 6/3/06
This Philco we believe is a 1938
model 38-7 based on the Rider's manual. It has proved to be the most
challenging radio repair job we have ever done! (Originally I thought
it was a 38-5 but later found it was likely a 38-7. There was no ID
inside the cabinet or on the chassis). If you see the file names for
the photos are "38-5" that was based on my assumption earlier that it
was that model. Please click the photos for larger views.
Here is a view of the chassis side during the repairs. Someone had
replaced the electrolytics probably in the 60's and used a plastic tube
to help fit an Admiral electrolytic cap in the old clamp.
We replaced all of the capacitors including those in the encapsulated
units and used terminal strips as necessary to mount the new caps.
The first problem upon testing was that there was a feedback squeal.
This was traced to a problem in the tone control circuit. Originally
there was a switch for tone control but someone in the past rewired the
circuit to use a potentiometer. We discovered a short in the pot and
found that the tone circuit was causing a positive feedback loop from
the output stage to the 1st audio stage and disconnected the modified
tone circuit.
Testing the Philco on the bench. We replaced the old frayed
high-voltage field coil speaker leads with new wire and bundled the
wires into heatshrink tubing.
Then we noticed that there was no audio after this problem was fixed.
We found the convertor tube was not lighting up and traced the problem
to a bad socket. Here is the area of the old socket:
We replaced the old socket with a new Vector socket:
After this the tube lit up like it should: Still there was no audio. We
used an alligator clip lead to bypass the volume control and was able
to receive stations, and found the volume control was bad. Luckily we
had a pot with a long enough shaft on hand.
Here is the Philco chassis being tested in the cabinet. We
re-insulated the IF tube grid lead with heatshrink tubing after this
picture was taken.
Here is the underside of the finished unit. We added a fuse holder to
the power line and reconnected an auxiliary jack previously added on
the rear to the volume control to allow a record player to be hooked up
if desired.
Tuning dial. The small knob on the dial moves the whole dial assembly
to tune in stations. This dial was customized with the names of
stations in the West Texas area. We also have tested the shortwave
reception which works well too.
Front of cabinet. The owner said the radio was bought in 1940 and that
he listened to it as a child...also he said several other shops were
unsuccessful at getting it to work. There has never been a tube radio
we couldn't get to work well...although this one had the toughest
problems of any we have seen.
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