I had seized an opportunity to check over my wonderful Collins R390A military communications receiver (and spy radio) and, prior to this video, I had removed the IF subassembly to check that the 'killer capacitor' already been replaced, which it had been (along with a couple other capacitors by the previous owner). So I made no changes. But after reinstalling the IF subassembly, the radio wouldn't work. I spent the next day on a frustrating hunt for the cause without any hint of what had gone wrong. Then, by a stroke of luck, I discovered the real problem the antenna relay. Once that is repaired, I focus on two important adjustments, the Gain and the Carrier Meter. Finally, I check the receiver's sensitivity and find it satisfactory and receiver ready for regular use.