Fan Hum

[Henz]

So I put a new verb tank (9AB2A1B) in my DRG C+ long head a few months ago and its so sensitive. When I turn up verb , with the cooling fan running, the fan makes a hum come through my speakers. Not a constant hum but gets louder as verb pot is turned up. Un plug fan, hum is gone. I put the rubber grommets in with new tank. I tried putting rubber washers under fan screws. Still there. Any one have any other suggestions? And, what made my new tank much more sensitive? If I remove that 120pf cap on V2A will that reduce verb some? I'm gonna put old tank back in and A/B them to see if it's new tank. Any help will be appreciated. Thanks, Jim. Side note: the original fan cord broke on male side so I soldered and heat shrinked a piece of extension cord (male end to plug in chassis). It's a little longer than original. Wondering if that may be an issue being so close to PT.

 

[Henz]

Update: after inspecting new tank on bench, I think I found issue. That carriage that has the verb springs was resting on bottom of tank. Not floating. I re sprung it via those four little springs holding it. Now it floats. Shouldn't this model of tank be open side up? The gravity will pull transmission spring unit down to tank. Anyone agree with me? I'll update tomorrow if anyone's interested. Thanks.