#1
Some Background...

I just bought a minty 1965 Ampeg Gemin I G-12 amp off CL. The amp was serviced earlier this year in Seattle -- some of the caps were replaced, part of the chassis (or circuit board?) was rebuilt, and the footpedal was rebuilt.

The amp sounds great at lower volumes but there are some humming issues I'll have to work through. It also needs a 3-prong cord installed.

The Issue...

Whenever I start to crank up the tremolo intensity, I can hear a regular, timed clicking/ticking noise coming from the amp. It's quite subtle at first, but as I turn up the Volume & Intensity knobs it becomes more pronounced. Its frequency is tied to the tremolo Speed knob setting. What could be causing this?
"In Power Trios I Trust..."
Gibson SG Classic, Fender CP Jaguar Special HH, '65 RI Mustang
'65 Ampeg Gemini I G-12 Combo, Orange Tiny Terror
#2
Aren't you giving the answer in your question?

Isnt the speed setting linked to it? Therefore slow the speed, see if it sticks with it, speed it up and vice versa, if it correlates then thats the problem?
#3
Come on, man. "What could be causing this?" = "What malfunctioning part or component in my amp could be causing this?"

The tremolo should not be clicking or ticking when I engage this effect. Obviously, based on my description the frequency of the click is tied to the speed setting and the loudness is tied to both the intensity and the overall volume. But any number of things could be at fault.
"In Power Trios I Trust..."
Gibson SG Classic, Fender CP Jaguar Special HH, '65 RI Mustang
'65 Ampeg Gemini I G-12 Combo, Orange Tiny Terror