Gearhead
Hi, me worried about me 274B rectifier tube made in China.
It's in a very very nice 300B hifi amp which has worked flawlessly for a year and a half now. Now I know these puppies are supposed to give you nice fireworks when warming up, but I do feel it should not go back to doing so after, say, half an hour should it?
If someone can offer me one I'd be much obliged. Even if just in case. Even if also from the People's Republic; I don't want to fork out WE bucks just yet.
Karel-Mars
Lightning in rectifier could also be caused by over load. How much current is your 300B's drawing? Check the voltage over the cathode bias resistor. If this voltae goes over the max rating for the bypass capacitor, the cap is going to cook.
Also check if the 300B grids are at 0V. I have seen Jensen oil caps fail (coupling caps) and causing the 300B to run hot and cook the cathode caps. All this would cause problems for the rectifier.
Otherwise look at your power supply caps for any signs of failure.
Gearhead
Hi Karel,
I have not checked any of the suggestions you have given, mainly because I just hope the engineers at Yarland have gotten it right and the power loading of those components is ok. More practically it would also require quite a bit of work to open up the casing ?
I think I found the cause in the meantime: the tube was not sitting straight up. I noticed this and had a look at the spacing between cathode and anode before switching off and removing the tube from its socket. Then I let it cool resting on its other side. Put it back straight up; playing fine now.
Do you have / can you get a 274B or should I contact Mrs. Valve?
