Woofer pulsating with no volume , Oscillation issue?

@erik_squires

ya , the left amp has a bias reading all over the map , should be 300 & its jumping radically...did contact Manley about all this, looks like it's headed back to the shop.....thanks

It could be nothing more than a bad tube. Try swapping them left for right first.

Start with the power tubes.

If it doesn’t follow the tubes, then most likely needs service.

I should add, the woofer pumping, and the bias bouncing around are most likely related.

@tommypenngotti 

A low frequency oscillation as you see here can be caused by failing filter capacitors in the power supply. If this is the cause it will get worse- the condition is known as 'motorboating'. If this is what is going on, I'd have both monoblocks serviced as its likely the caps in the other channel will follow suit soon.

@atmasphere 

just replaced all the caps about 6 months ago , thanks 

@tommypenngotti Did you swap the input cables left for right to see if the problem moves?