Berning ZH270 help

DId you switch tubes from one channel to the other to see if the problem changes channels? If you did and it stays in the same channel, it's probably not tubes. In that case I'd get in touch with David Berning or Allan Bhagan.

If one of the tubes are not within it's spec, the amp will see it within 1/60 of a cycle and continue to try and correct it within every 1/60 of a cycle while limiting current to the tube, which turns the LED red, if you turn the amp off and then on again and the problem is gone for awhile, that could mean the tube warmed up and is now operating within it's specs.

So as Oneprof suggested, please swap the tubes from one channel to another and see what happens, I suggest only doing the outputs firsts and try it that way for a while and see what happens.
It would also help to know the age of the amp.

Please feel free to e-mail me.
Allan

Thanks for your kind and appreciated help. I've forgot to tell I tried to swap the tube, power first and pre after but the problem persist on just left channel. It remembers me once when I had one cap gone with another amplifier...
I'm in contact with a good service here in Italy, I'll take my ZH270 there.
Hey Allan, I'm Paolo from Italy...you may not believe but I've not yet received your post. It should arrive anytime these days....Italian Post Office....

Paolo, the noise you describe really is conducive to that of a tube problem, you need to take your time and switch one set at a time, and make sure you are changing them from one channel to another, as well, did you do any mods to the amp?
The ZH-270 is not a user friendly mod device by any means.

I hear stories from Europe of people cutting off the wrappers on caps and other stuff.

When you get the other set of tubes, we can go through the switching, so we can make sure it's in opposite channels.

Thanks Allan,
Just received your tubes and kit today, I'll install and see if it solve also the Left channel problem.
Anyway, no mods made on my ZH270, only preampli stage tubes swap. Im my ampli there was 1x 12AV7 RCA Electron Tube, 1x 12AV7 Internation Service Master (2 different!) and as 12AT7 2x WC GE and 2x JAN Philips.

As mod I'm thinking on signal cabling upgrade with better cable (the one used is quite bad actually) and maybe a better potentiometer, I could heard astonishing improvement with an Imai (Audiotekne) precision carbon resistor one.

I had to service it one year ago when a transistor in PSU was dead, but in the case the ampli didn't wanted to turn on: always red leds.

Paolo