[TerryB44]

Good Morning everyone, My, you're all up early! Before I go any further I must thank everyone again for all the input you're giving to try and sort this for me. I have to admit to be somewhat of an electronics virgin in the sense of Eric Morecambe playing all the right notes but not necessarily in the right order!
However, be that as it may, I have learned a lot from all the things that I have been asked to check in the search for a solution. It reminds me of what Sherlock Holmes once said, that once you have eliminated the impossible what ever you are left with, however improbable, must be the truth!
Now, back to the problem! Below is a zip file containing audio. What you will hear is the 50Hz hum in play setting at 3 3/4ips followed by hum at 7 1/2ips, switching back and forth a couple of times, and then with tape playing at 3 3/4ips. The volume control was set at 12 o'clock, half way, throughtout.