"Bendzh" wrote

[Leitz V35] head makes a buzzing sound whenever the light's on and the
enlargement intensity fluctuates slightly.

If you are sure the buzzing is in the head the most likely cause
is a loose connection. Usually:

hissing buzz = loose connection, arcing
rattling buzz = loose transformer core, relay or hardware
humming buzz = loose transformer coil

Is the buzz constant? Happen all the time? What happens
if you give the enlarger a slap [like an old TV set]?

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.nolindan.com/da/index.htm
n o lindan at ix dot netcom dot com