[Collins] 75A4 sensitivity

[Dr. Gerald N. Johnson, electrical engineer]

What does the 75A4 have for RF stage? IF stages? Are they the original
types? Is the screen bypass on the RF stage paper or disc ceramic and
are its leads short? Also the plate feed bypass? Is there a 100 ohm
resistor in series with the grid?

If the screen bypass has short leads and is a disc ceramic, and the
plate supply bypass is the same, and it has the right RF tube (no 6EJ7
or 6EH7), then I suspect a VHF parasitic oscillation. Adding a 100 ohm
resistor in series with the control grid may help. It would help to be
sure that the input tuning is actually to the signal frequency.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.