Thumpy Trem on Lazy-J 20- now sorted

Colms2005

I was wondering if anyone can shed some light on a small problem I am having with the Trem module on my Lazy-J 20
I recently removed the tremolo module by unscrewing it from the cabinet (but not unwiring it) to allow me to swap out the speaker for a new Celestion Blue.
The Trem is now helicopter sounding/thumpy if I add more than a quarter of the intensity knob. At lower intensities it sounds fine.
It wasn't like this before I swapped the speaker. The speaker isn't the culprit however because it sounds fine without the trem being engaged.
I have swapped most of the valves for known good valves including the rectifier. The only tubes I haven't swapped are the 12AX7's on the reverb. There is a small screw located on the top of the trem module and I don't know what that is for.
Jesse has been very good to help me in the past with advice but I thought Id ask here first.
Thanks in advance.

StuartMac290

I had this with mine and had to send it to Jesse to fix it. Give him a call. 

Colms2005

Cheers Stuart

Majorscale

The trem can get thumpy if the VAC is on max and the trem intensity is high. Try to open the VAC a bit and see what difference that makes. Although this may be something else since you removed the unit...

Colms2005

Thanks Majorscale I appreciate it

Colms2005

I backed off on the VAC and the Trem is perfect again. Thanks for everyone's input.