[Steve Davis]

Tim, before you pull the IF, check trimmer number 19 on the second IF to be sure it has a good ground. A few years ago, I had an intermittent problem with the IF on a 70. It has been a long time but, it seems that there was a steel tab on the trimmer that had some rust that was causing the ground connection to be intermittent. You might try connecting the trimmer to ground with a clip lead to see if the problem goes away.

Steve