Marshall help

[Fireboxx3]

I have a 1984 Marshall JCM 800 2204. Today I changed power tubes from JJ EL34s to new production Svetlana EL34s. Now I have a fizziness on the low sensitivity input and whenever I turn the volume on the guitar down on the high sensitivity input to get a clean sound. I basically can’t get a clean sound anymore. It didn’t do this before I changed and biased the power tubes.
Please help.

 

[CrazyNutz]

Are you checking with a bias probe? So you can check the current draw of each tube?

If so make sure they are both drawing current, and not super far our from one another.

Next re-seat the preamp tubes, if you have a spare preamp tube, try it in all three spots and see if the problem goes away.

If still having the problem, put your jj's back in, and if that clears it up send the svetlana's back.

 

[MetalHeadMike]

Are you checking with a bias probe? So you can check the current draw of each tube?

If so make sure they are both drawing current, and not super far our from one another.

Next re-seat the preamp tubes, if you have a spare preamp tube, try it in all three spots and see if the problem goes away.

If still having the problem, put your jj's back in, and if that clears it up send the svetlana's back.

^^^
Kind of what I was thinking.

 

[Fireboxx3]

Are you checking with a bias probe? So you can check the current draw of each tube?

If so make sure they are both drawing current, and not super far our from one another.

Next re-seat the preamp tubes, if you have a spare preamp tube, try it in all three spots and see if the problem goes away.

If still having the problem, put your jj's back in, and if that clears it up send the svetlana's back.

I did check with a bias probe when i put them in. I changed the preamp tubes and that didn't make the fizziness go away (tried tung-sols, Sovteks, Electro harmonix, and JJs). So, i'll try checking the bias again and if it's all out of whack, put the JJs back in.