highroller
Well-known member
I'm a proud owner of a Mark IV "A" 1991.
Today, I noticed a small blue spot on the glass of one of the 6L6 inner tube, there is also a very thin blue line in the center of the same tube.
It look like a blue fluorescent spot coming from the inside of the tube.
I replaced this blue tube with another working 6L6 and I still get the same strange blue spot. It seem to be more apparent in Simul-Class, Pentode, Full power.
I just installed a new pair of KT-77 in the outer position and I'm wondering if a faulty tube can cause a bias imbalance ? Or maybe a resistor is dying in the power section ? I'm thinking about replacing the old carbon comp resistors with newer metal film, any suggestion ?
I may have never noticed the blue tube because it is not very apparent, it can be there since a long time. Not sure however if I'm not slowly destroying my output transformer or other expensive part...hope not !!!
Thanks
Today, I noticed a small blue spot on the glass of one of the 6L6 inner tube, there is also a very thin blue line in the center of the same tube.
It look like a blue fluorescent spot coming from the inside of the tube.
I replaced this blue tube with another working 6L6 and I still get the same strange blue spot. It seem to be more apparent in Simul-Class, Pentode, Full power.
I just installed a new pair of KT-77 in the outer position and I'm wondering if a faulty tube can cause a bias imbalance ? Or maybe a resistor is dying in the power section ? I'm thinking about replacing the old carbon comp resistors with newer metal film, any suggestion ?
I may have never noticed the blue tube because it is not very apparent, it can be there since a long time. Not sure however if I'm not slowly destroying my output transformer or other expensive part...hope not !!!
Thanks
