Drake R-4C Receiver

Symptom:  Receiver sensitivity was about half what it should be. Switching over to the T4XC VFO and the sensitivity was normal.

Fix:  Diode CR5 located between V6 plate and grid was defective. It’s very hard to get to this diode, so care must be taken not to damage any of the surrounding parts. 

Drake R-4B Receiver

Symptom:  Power output was lower when operating off of the receivers VFO than the T4XB.

Fix:  R46, R103, C34 could have changed value.

Drake R-4 Receiver

Symptom:  Power output was lower when operating off of the receivers VFO than the T4X.

Fix:  R7, C20, or C136 could have changed value.