SP14 losing right channel when warm

Hey everyone,
I’m experiencing a problem with my SP14. Everything is great until 1 to 2 hours of listening then the right channel cuts out. I run 12SN7 tubes and leaning to those tubes as the culprit. Any suggestions?
Thanks Dave

You mean 6SN7s, right?

I had the same problem with my SP 14. Is your SP 14 an older unit?

I ended up sending mine back to Roy twice. Mine was a very early SP 14 and the old ones had an un undersized heat sink and an an out of spec filament transformer.
That may or may not be your problem.

Thanks all.
I checked all solder joints tonight. Nothing looked bad but just to be safe I resoldered all the tube sockets, the power transistors, and everything that could be suspect. I only had time to play 1 lp, it worked fine but tomorrow I’ll let it play for a few hours and keep my fingers crossed!
Dave, I run 12SN7s, they are essentially the same but operate at 12v instead of 6v and can be bought for less.
Oh, I also checked all voltages on the build sheet. Everything looked good both when first turned on and after being powered for 2 hours.
Again I will test tomorrow.
Thanks for the feedback!

Hey all,
I still have the problem. Yesterday I checked and resoldered, today it again lost the right channel after it warmed up. I have installed new tubes (including the rectifier). Any suggestions?
Dave, I checked all voltages when warm yesterday and everything seemed okay so probably not the transformer?

I'm not a tech but my SP 14 was doing exactly what yours is doing as I said.
How old is your SP 14? Is changing over to 12SN7s a common mod?

Like I said. Roy had to work on mine twice.

Hey Dave,
My unit is about 7 years old so it could be the transformer. My thinking is if the voltages were correct after warming up yesterday the transformer should be okay but I think I will perform another voltage test tomorrow after it has been powered up for at least 2 hours.
I would say the 12SN7 is a fairly common modification and was suggested by Roy at the time of purchase. I just purchased 4 NOS 12SN7s for under $30.