[Amps] ACOM1010 Xformer growling

[Tack JE1CKA]

I had a very clean used ACOM1010(a 4CX800, 160-10m) amplifier yesterday  
with $500US. It runs fine but a following issue.
A transformer is growling very badly.
When the amp was keyed a transformer started to growl, and it was driven  
50-60w input a roar became terrible.
I checked the fix bolt of the transformer and found nothing wrong.
How to fix this transformer growling.
-- 
Tack Kumagai, JE1CKA