Question: "I placed the 420STR on the record and hit the 'mute' and that's when an almighty noise erupted." Is this step #5? You just placed the 420STR on the LP and then un-muted?
I presume the tt was activated, platter was turning. Yes?
Can you characterize the crescendo of "noise"? Was it low frequency, high frequency, etc? Was it like what one hears at, say, a rock concert where the sound man is trying to adjust the mike and one can get that obvious microphone feedback between the bass player's speaker and the microphone, a "screech"?
Since your unit is already being repaired, I suppose all this is moot, but it might be a good idea to try to hash it out so the problem does not repeat itself, I guess.
I presume the tt was activated, platter was turning. Yes?
Can you characterize the crescendo of "noise"? Was it low frequency, high frequency, etc? Was it like what one hears at, say, a rock concert where the sound man is trying to adjust the mike and one can get that obvious microphone feedback between the bass player's speaker and the microphone, a "screech"?
Since your unit is already being repaired, I suppose all this is moot, but it might be a good idea to try to hash it out so the problem does not repeat itself, I guess.