We have about 35 different schematics we have Mod from older Plexi's we have serviced. Everything varied on those amps. The cap and resistor values varied (which is commonly known) but the transformers varied a great deal.
Back in the day Marshall was a small business and as a means to save money they would go into the local military surplus store and purchase a dozen transformers from the cut out/bargain bin. They would build a dozen amps, ship them out and then go back and buy a dozen different transformers. Some times it was mix-n-match, etc. Add to this that the capacitor values and type (what they are made of) also varied a great deal. Resistor values varied as did the over all power supply design. When you add up all these variables it makes perfect sense as to why it's so difficult to find two old Marshalls that sound or feel the same.
When we found a Marshall that sounded stunning we decided to offer it as a production model so that others could have a great sounding plexi right out of the box
If you have any other questions please feel free to post them or email me directly at
trace@voodooamps.com. Questions are more than welcome and also please feel free to call us.
Thanks!
Trace