DC - 3 volume Issue

I have two DC -3 1 x 12 combos...I had to purchase another because after owning one of these amps, no other amp does it for me anymore

The original one i brought a few years ago had an issue with the tubes red plating, and i got the info from here to mod it and it has been great since. The second DC3 has a different issue:

The amp sounds basically identical to my original one, tone is fine on both channels, but the volume is way lower. I can crank the output level up to 5 and beyond, while the other amp knocks your socks off at 2 -3. (I am running these in stereo through a boss BE5)

It has been to the local amp tech twice and still no luck

A list of everything that has been tried so far:

Have bypassed all effects (Guitar straight to amp)
Replaced optocouplers
Replaced a resistor in the clean channel
Tested the pots
Replaced all tubes(Swapped with tubes from other amp)
Connected speaker from other amp
Amp tech has tested output amp and it is outputting 35watts

The only thing i have noticed is there is a slight crackle coming through the speaker on this amp sometimes??

Any help with this would much appreciated as the amp tech here is scratching his head

Cheers
J

Some caps are dead

Ok thanks for that mate, i will give the amp tech a call tomorrow.