Model 16 Oscillator Failure
On
some models of the Philco 16 All-wave Receiver, difficulty was experienced
with failure of the set to oscillate [the local oscillator/mixer stage]
at the low frequency end of the two top bands.
Investigation
in one case showed a high resistance between the rotor plates of the tuning
condenser and the chassis. Although there are several grounded points for
this connection, a small amount of corrosion had set in and introduced a
relatively high resistance. By tightening the screws, this condition was
entirely eliminated and the set played correctly.
In
another case, it was found that corrosion had become imbedded under the
bakelite washer on the gang compensating condenser at the front of the chassis
(10.8 megacycle adjustment). By removing this washer and cleaning it thoroughly,
the trouble was entirely eliminated. It was, of course, necessary to readjust
the short-wave compensating condenser.
On
one Model 16, it was found that the antenna series condenser No. 5
in the wiring diagram of Philco Service Bulletin No. 165 was open. Another
set had an open coupling condenser in the plate circuit of the oscillator,
No. 26, Service Bulletin No. 165. A Model 16 which was
weak on the low frequency end of all bands was corrected by reducing the
value of the resistor in series with the oscillator plate (No. 27)
from 50,000 ohms to 30,000 ohms.
From the Philco Serviceman - May, 1934.
