HELP - I am the proud owner of a tubes4hifi PAS preamp and have a puzzling problem

.
The other evening while listening to music, the output just disappeared.
After I took off the cover and plugging
it in, all the tubes were lit.
To make sure it wasn't the tubes, I swapped them out with known goods,
I reinstalled in the rack. Still no output. .
Checked all the solder joints and found no faults.
Please help.

Thanks

I just pm'd you