looking for help Dynaco st 70

i am a complete novice but love the sound of my tube amps! i am running a turntable, a dynaco st 70, and a conrad johnson preamp.
i recently lost one channel  
i bypassed the conrad and hooked an ipod directly to the st 70 and confirmed its only playing out of one channel
i also switched the speakers to confirm i did not blow one of those or have a lose connection
All tubes removed and put back in  all are lit
i also switched the left and right
still only one channel

if i switch it to mono....still only one channel
can anyone advise of the next step before i spend 150.00 per half hour at our local tech service?
thank you

You will get some excellent help here but you will have to get as detailed a history as possible and other info on the amp. Better know where it came from and any modifications before you got it or be able to open it up look around and figure it out. Also you don’t have to be a pro but you need to be able to run a soldering iron and a VOM meter to take some measurements and talk somewhat in electronic terms. Read the stickies above. Otherwise it’s gonna be $150 an hour.

pattirules wrote:i am a complete novice but love the sound of my tube amps! i am running a turntable, a dynaco st 70, and a conrad johnson preamp. >>>>>SNIP >>>>

At least you are half way there. Back in the Cretaceous, I auditioned a friend's Conrad Johnson on my ST-70. The combo was excellent.

IMHO, you are going to need the Dyna Kit build manual, a decent VOM and some alligator clips so you can do some current measurements in the circuit. BUT ... if you are not comfortable, or have not had instruction about working with high voltages, get a tech person to diagnose the problem. Then you can do the repair yourself. Better minds than mine can aid you here. Please be safe!

Lorne