hey ive got a randall rg50 tc, and ive changed the tube el34's from the stock ones to some free mesa boogie tubes el34's, however the amp keeps blowing one of the tubes without blowin the fuse, any ideas about biasing the amp, ive tried placing the same as the stock tubes electro-harm, the same thing happens. i dont really want to put anymore without ideas. anyone with any ideas would be a great help.
You need to rebias every time you replace power tubes. It's not very hard, all you need is a multimeter and probes (and nowadays they make sockets for biasing that have all the problems already hooked up to the correct pins).

But you may want to have a tech do it for you.
There are many guides to rebiasing online, and there are different ways to do it. Most people go by the cathode resistor method as it is safer and easier but if you don't know what you're doing, I wouldn't go poking around inside your amp as there are very high and very lethal voltages going through your amp as well as high and lethal voltages stored in the amp even when it is turned off and unplugged.


You can't stop your power tubes from burning out unless you bias to a safe range. The tubes that you've put in there are already toast. Every tube is different, doesn't matter if the types or brand is the same.