marshall jcm900 valve pin voltages

[paulgolding]

Hi

does anyone know what the correct voltages are on the pins of the output tubes ?

or a link to a schematic with them on ??

it's the marshall jcm900 4500 model.

many thanks

Paul

[paulgolding]

anyone any ideas ??

[Enzo]

They would be about the same as any other amp with similar tube complement. I would expect something in the 480v area for pins 3 and 4 on the power tubes, and something like -45 on the grids which are pin5 on each.

If you are expecting a schematic to say 478v or something, they won;t. At 480v B+, every 1v of change in the mains voltage results in a 4v change in your B+. My mains are sitting at 123VAC at the moment, so my B+ would be 12v higher than someone whose mains were right at 120v. These mains voltages change minute by minute. I sure wouldn;t worry about 20v there.

I think he has your schematics here: http://www.schematicheaven.com/

[paulgolding]

thank you enzo