A&R of cambridge SA200

[bosedtobosed]

i have an unusual effect with the sa200 power amp, when a record is cued and the arm dropped there is a buzz\hum thru the speakers as the needle touches the record, this reduces to an almost inaudible level for the duration of the record, only when using the sa200 and only when a t\t is being used, as there is a large almost dc component to the signal at that moment is there a dc zeroing cct being used, there is a CA1458 op amp on board, (ie a LM741) but i dont have the cct diagram to verify this, if so why does it buzz\hum, anyone come across this phenomenononon !