LSC hum from reverb Ch1 only

Hi guys,

have noticed a definitely louder than normal hum has developed on my 2005 LSC, which increases as the reverb level is turned up, but only on Channel 1. No hum from reverb on Ch2 at any level.
I have replaced V4 but makes no difference. When V4 has been on its way out before I had a hiss on both channels' reverb, but this is a smoother hum.

Anybody got any ideas before I email this one across to Mesa.

Appreciate any input

Thanks

The only thing I have for you is to try changing out your V1 & V2 preamp tubes.