Ampeg reverberocket r12r Reverb issue..

[Randybobandy]

Hello all, I'm new here, have the aforementioned Ampeg amplifier, I do like it a great deal. Only concern is that when engaging reverb, it does not "turn on" until 4, and its faint. 7 is a okay spot in the dial, and 10, well 10 is 10, if never experienced a amp's reverb not kick in until 4. Actually just swapped thanks yeterday with a new tank. And it's a shorter decay, so even less percieved reverb. I do plan on putting a new tune in the phase inverter, but these tubes arnt really toast either, so is there something else I should be looking for? Something in the circuit?

Thanks to all that read and participate. 
I'm new here!