5150 III head problem

[z1n]

Well I was playing for about 10 minutes and all of a sudden the power dropped down and didn't sound the same. Gain was a little over 3/4 and main volume was just under a 1/4 on channel 3/red. wasnt playing very loud at all. So I started changing the settings and noticed when I turn up the treble knob the amp gets quiter with no treble increase. When I turn the treble knob down the amp gets louder   Could this be a tube? Any help on this would really be appreciated. I've changed tubes before and biased heads but this head, I have never touched. I purchased it new maybe 3 years ago from AMS. Thanks for any help

[z1n]

Oh one more thing, channel 1 and 2 are fine it's just on the lead channel. I just tried it again after leaving it off awhile and same thing. lead channel, the treble knob is acting like a volume knob but amp gets louder when you turn treble down and gets quiter when you turn the treble up. Other channels are fine. Thanks

[metalhobo]

Could this be a tube?

yes. replace the power tubes

[z1n]

thanks metalhobo I will do this

[jacksonaxes]

I think you should try pre amp tubes, one at a time. Since the other two channels are fine.

[metalhobo]

I think you should try pre amp tubes, one at a time. Since the other two channels are fine.

I missed the second post where he said this. yes this is correct. if some channels are unaffected it's probably not the power tubes.

[z1n]

Ok I have the power tubes coming. I guess I will go ahead and replace the rest as well. Didn't want to spend the money but it makes sense to go ahead and do it. Thank you guys for your help!

On a side note I ordered the JJ 6l6 as that is what I read was in these but after looking over the tubes you can see a very faint GT on the glass so it did have groove tubes in it.

[catzodellamarina]

When I had winged C Svets in mine, it roared. When they bit the dust, I was forced to go with less expensive and stock replacement JJ's. I was shocked at how "tame but not lame" the JJ's made the amp sound. They work fine but are definitely less impressive than the Svets. When I need to replace them again, I WILL be colluding with the Russians

[z1n]

Are these them? https://www.thetubestore.com/winged-c-sed-6l6gc fuk they are $99 each! I did get the JJ PT's but I still have the problem so I need to get the 7 pre amp tubes. Any recommendations?
I found this but not sure http://www.dougstubes.com/preamp-tonekit-12ax7-7.html

[DonP]

Winged C's are not longer made. That is why they are so much.