Modifying to 220V operation. How to make sure?


Taking the bottom cover off my VTL MB100 I've noticed the extra set of isolated wires from the power transformer.
I called the manufacturer and they were not able to be clear since they do it usually as extra feature having an option to re-wire the unit to 220...240V operation.
There is some plan on how I plan to verify that the unit will operate at 240V and I want to discuss it.
1. Make sure that rectifying bridge is able to operate at 240V if not than I would have to replace it(or even upgrade).
2. Take off all tubes
3. Reconnect wires from the power transformer and turn on the amp into the 220V receptacle.
4. Check Cathode voltage from the tube sockets(Is it safe to run amp with no tubes? What issues am I facing here?)

If I need to replace bridge what parameters should I provide the manufacturer(of the bridge) becides input-output voltage and tolerance%?
128x128marakanetz

Showing 1 response by herman

Even with the tubes removed you still have the potential to do some serious damage. If you do it wrong and plug it into 220, you could have twice the normal DC voltage in the amp. That means twice the normal DC voltage across the filter caps. In my amp that would mean going from a B+ voltage of about 500 volts to 1000 volts. This is sure to be more than the maximum rating and since electrolytic capacitors tend to explode when they have too much voltage across them, you may have a real mess. No telling what else would be destroyed. Perhaps you.

Marakanetz, you seem to know just enough to be dangerous. I mean that in the nicest way. I admire your inquisitive nature and your desire to improve your system. But you are going into areas that will result in disaster unless you know what you are doing. Perhaps you could get some textbooks on basic electronics or take some classes at a community college. Once you have a better understanding of what is involved then you will be better equipped to redesign your amp.