Adrian Tuddenham wrote:



Don't make the mistake which comes around time and again* of switching a
charged capacitor directly onto a discharged one, the switch won't last
long.


** You mean like the Mesa Boogie MkI model does ??

http://bmamps.com/Schematics/Mesa_Bo..._Schematic.pdf

Note the 60F, 500V electro fitted AFTER the standby switch !!

The main electro bank is inadequate ( 2 x 60uF, 350V in series )so someone decided to add an extra cap. There is a loud *snap* whenever the standby is closed and it soon burns the hell out of it.

Later versions used 2 x 220uF in the main bank and a 0.1uF 600V film cap after the switch ( so from OT centre tap to ground ) which sometimes fails short.

For sheer stupidity it is hard to beat early 70s Marshalls that switched OFF the bias supply with the standby.

http://bmamps.com/Schematics/marshal..._year_1970.gif

While the 400V HT come up instantly, output valve grid bias take 3 or 4 seconds to arrive !!


..... Phil