I had this radio stored away, about a year ago after a recap and tune up, was working grand. A friend was looking for one, and I knew I had one, so I pulled it out, hooked it up, it was Rx and tx fine for about 15 minutes, then Rx went silent, light fizzles coming thru the Rx. Hmmm.
I knew the pll was locked as the tx was perfect and on frequency. Made sure the mic wasn't causing the issue. Checked all screws for tightness. Decided to check the attenuation diodes, looks good. Then to tr17, the 1st RF amp. Voltages looked good. Went to tr18, the mixer, had good collector voltage, but 0 volts on emitter and base. Aha! That base gets it's DC from r82. Other end of r82 showed correct voltage, and it was not open. Checked for a shorted r81, which would pull that base to 0. Nope, 10k. Last thing to check was c57 for a short. Bingo! C57 showed random resistance between 0 and 180 ohms.
Replaced c57, Rx restored and life goes on.
I knew the pll was locked as the tx was perfect and on frequency. Made sure the mic wasn't causing the issue. Checked all screws for tightness. Decided to check the attenuation diodes, looks good. Then to tr17, the 1st RF amp. Voltages looked good. Went to tr18, the mixer, had good collector voltage, but 0 volts on emitter and base. Aha! That base gets it's DC from r82. Other end of r82 showed correct voltage, and it was not open. Checked for a shorted r81, which would pull that base to 0. Nope, 10k. Last thing to check was c57 for a short. Bingo! C57 showed random resistance between 0 and 180 ohms.
Replaced c57, Rx restored and life goes on.
