Orange Thunderverb Repair - Bias circuit modification and Fun with Phase Inverter tubes!

In this video I go through the steps of finding out why there was low volume in this awesome THUNDERVERB 200 amp from ORANGE. Nothing major needed repair however the customer's tubes were not falling within proper bias range. This is correctly easily by lowering a resistor value in the bias circuit and we need to perform the work in a manner that is easily reversible if needed in the future.
I also discovered the previous owner had installed a 12AY7 tube in the phase inverter position. This tube has much lower gain properties than a 12AX7 which will ultimately yield less phase inverter distortion. I thought it sounded really good this way so I took some sound clips of the effect each tube had on the overall sound. The customer ultimately wanted to go with the 12AX7 that the amp is designed for in that position since that's the stock part.
This one has been through some rough times but it gets a clean bill of health and has been sent on it's way.