01-24-2006, 04:53 PM
Gents,
Final update on the status of a Philco 70A.
After completing a detailed checkout of the wiring, solder joints, components and collecting voltage readings on all the tubes, I have pinpointed that the voltage reading at the 2nd detector screen Grid were way to high and confirmed that the 2nd detector Screen Grid capacitor and resistor were missing.
Obviously, I was not the first one who troubleshooted this receiver and someone omitted to insert these critical components.
Lesson learned: Do not trust any previous repairs.
These two vital components are essential to provide proper bias to the 2nd detector tube.
After proper insertion of equivalent component values, the 2nd detector tube voltage readings were brought to the established parameters as indicated as per the Philco 70A diagram voltage table.
The frying background noise is now unnoticeable and the set receives very well on the whole AM band. Please note this set has no AVC, therefore the local station are very loud and clear. Distant stations reception level are comfortable.
I wish to express my sincere thanks and acknowledge the fine support of thoses who provided me with sound technical advises in order to cure this set.
Regards
Recepteur.
Final update on the status of a Philco 70A.
After completing a detailed checkout of the wiring, solder joints, components and collecting voltage readings on all the tubes, I have pinpointed that the voltage reading at the 2nd detector screen Grid were way to high and confirmed that the 2nd detector Screen Grid capacitor and resistor were missing.
Obviously, I was not the first one who troubleshooted this receiver and someone omitted to insert these critical components.
Lesson learned: Do not trust any previous repairs.
These two vital components are essential to provide proper bias to the 2nd detector tube.
After proper insertion of equivalent component values, the 2nd detector tube voltage readings were brought to the established parameters as indicated as per the Philco 70A diagram voltage table.
The frying background noise is now unnoticeable and the set receives very well on the whole AM band. Please note this set has no AVC, therefore the local station are very loud and clear. Distant stations reception level are comfortable.
I wish to express my sincere thanks and acknowledge the fine support of thoses who provided me with sound technical advises in order to cure this set.
Regards
Recepteur.
