Upgrading the VHT "WATTS" Circuit

[Looselectron]

The SV2 we supplied has a tweaked resistor value to allow the use of the 1M dual pot in the VHT, as the other section is used to proportion the tremolo modulation signal applied to the output tube grids.

Step ZERO is getting the amp to work without WATTS, and "Assure the amp works properly before doing the SV2 + VCK installation." 

Unfortunately there are no clear instructions for this. So I started by yanking out the unnecessary parts.    

Before diddling around with the most lethal part of the circuit, I contacted VHT about the removing it. They sent me the following image but those extra diodes were already on the board! This is for the Special 12/20 (sans RT) so R56=69(B+3), R59=67 (B+1) and R55=64 on the Special 12/20RT schematic.     

So I jumped jump D13/R64 to R67 (B+) and the OT center tap to C49 (D14/B+1). R65 and R66 are now omitted. I hope the additional diode in the supply line compensates for the absence of the VC MOSFET between B+ and B+1 but is a 0.7V  drop still necessary here? Note the daughter board in the upper right corner erected like a car bonnet.     

That left a brown wire from TREMOLO (left lug) and a RED wire leading to TREMOLO OUT on the daughter board. I wanted to splice these but the brown wire just fell off... Jumping TREMOLO OUT to the left lug of the TREMOLO pot was the right move anyway. There was one more stray red wire I had to connect from the reverb transformer to B+2 but the reverb buzzes now even after reorienting the chassis...this has always been a confusing part of the amp for me but I do like the sound of this reverb.     

The amp sounds fine without reverb but until I can get that working 'properly' again, I'm gonna install the VCK separately into my newer VHT Special 12/20RT combo that hasn't failed...YET. I never fully understood how important heat management is in electronics until I started this project. Instead of drilling a hole in the chassis, I took apart a broken induction heater to look for a heatsink. This one might be overkill, but there are probably a lot of other good parts for guitar amps in there including a FAN.       

More updates to follow...