[Heathkit] Impedance Bridge

[Lee Bennett]

I have a Heathkit Impedance Bridge Mode IB-2A.  I am looking for the
instructions on how to operate it.  If someone has a manual, I would be
very thankful if you could scan the operating instructions and send them
to me.  I also have a SB-220 amplifier that is only outputing 500 watts. 
I can remove one tube and still get 500 watts.  It does not matter which
tube or which socket I use.  One tube 500watts, two tubes 500 watts.  Does
anyone have any idea what is going on?