[QUOTE=Kiwick;2230060]Then, the vertical deflection works fine but sometimes collapses to a bright horizontal line while changing VHF channels, is this normal?[QUOTE]
No, this is not normal. More than likely there is a bad connection that is breaking with the vibration caused by the ratcheting action of the tuner. Cleaning the sockets and pins of the vertical output and vertical oscillator tubes may knock it out. If not you can take an INSULATED tool and gently tap the tubes while the set is playing. EVEN WITH AN INSULATED TOOL WATCH WHERE YOU PUT YOUR HANDS IN A LIVE SET!!
A tube with an internal short of some sort will react to the tapping in the same way as the reaction caused by changing channels, only now you more than likely have isolated the problem with the individual tapping. Beyond this there is always the possiblilty of a bad solder joint or even a broken or dirty potentiometer. The faulty tube or dirty pins/socket is the most likely cause IMHO.....
I hope this helps...
