Marshall JVM 410 problem after install a choke

[Rod]

Hello!

I installed a choke in my marshall JVM410H, and after that the amp almost has no volume at all, i have to put the volume almost in the max to ear something, Could this be from the choke? and how can i check it?

I installed a Hammond 159S 4H at 225 ma.

Thanks.

[Enzo]

Check at the power tubes, do you have solid B+ at BOTH plate and screen grid pins of each socket? My first guess is you installed the choke in place of a resistor between plate and screen nodes, and some error was made.

[Helmholtz]

If you correctly installed the choke in place of the screen node dropper resistor, volume should not drop at all.

Please post schematic and voltages at both ends of the choke.

Edit: Missed Enzo's post above.

[vintagekiki]

Marshall JVM Schematics

http://musiciansroadhouse.com/viewtopic.php?t=11597

1)
http://forum.metropoulos.net/viewtopic.php?f=25&t=21932
2)
https://www.dropbox.com/s/n1gqurjb5eg1qmq/JVM4xx%20Schematics.pdf?dl=0

[Rod]

I have ckecked the voltages and everything seems fine with the choke , At both legs of the choke i got 560 volts, i also have voltage in the screens resistors. So it must be something else right?

[vintagekiki]

The Choke fitting mod for the JVM410H

https://tonymckenzie.com/marshall_jvm410h_review.htm

[Jazz P Bass]

So you did not remove the circuit board to do this 'mod'?
If not, then you may have a bad solder connection on the bottom side of the board.
It was stated that there is 560 Vdc at both 'legs' of the choke but do you have the voltage AT the screens?

[vintagekiki]

Questions
How much voltage is on WP14; WP15 (stby switch).
Check that the connectors and cables on the MB are correctly returned in their places after the choke is installed.

[Rod]

Hello and thanks everyone, the problem was a bad V2 preamp tube.

[Jazz P Bass]

Thanks for clarifying the resolution!