Question in regards to Bias and Fuses

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Dallas Marlow

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I have two pretty easy to answer questions:

First, I read on here to upgrade the fuses from the standard 250 to 400-500, I put the 500's in the tube fuses, are these too high because I now notice that most of the posts are saying 400s, the 500s are fast blow and it's all I could locate.

Second, according to the Randall Manual the highest you should bias standard EL34's was either 38 or 39, however; from all my previous knowledge I thought that 45 was the appropriate way to go with el34's, I notice it says up to 45 with EL34L's but not EL34's, which I REALLY don't get because don't the EL34L's draw a lot more plate voltage than normal EL34's? I've noticed when swapping between the two you have to turn your bias up a significant amount to get it into the same range as the EL34L's. I heard 45 was on the hotter side, but not out of a safe range, and that is just with standard EL34's, I believe that was according to Marshall for their DSL series.

Is running my Shugwang EL34-B's safe up to 45? This is what they are currently running at, amp doesn't seem to get to hot, sounds beautiful and runs great, and I do 3 hours of pretty high volume band a few nights a week along with gigs etc. no issues as of yet.

Thanks for your help!

Dallas
 
I don't have a definitive answer but I do know EL34s run hot anyway and if you look at the power rating and plate voltage you are running them on the high end at 45...EL34 is a 25W tube right, which makes 50mA with 500V plates = 100%?, 45/50 = 90%

Your tube lifespan will be lower and since tube quality is generally agreed to be very variable today you could be risking blowing something..hopefully the fuses kick in first.
 
Thanks for the reply man, but does anyone else have any input or know about the fuses?
 
I would think that the 500 fast blow would be fairly safe but at the price of putting more stress on the other components before it blows if there is ever a fault. The 250 fuses were obviously to small in some cases but the ideal is you want a fuse big enough to handle random peak surges but small enough to blow before something else does.
 
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