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Post subject: Blues Junior Valve concern
Posted: Fri Sep 24, 2010 9:37 am
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I have a Blues Junior and I noticed one of the EL84 Groove Tubes does not light up. Looking from the back it's the one on the left.
Is this normal or is it a sign of a problem with this valve. My amp is only 1 year old and has only been used for home use.


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Posted: Fri Sep 24, 2010 10:14 am
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Totally dark? Have you tried swapping tubes or just removing the dark one and reinstalling it?

If the tube is dead, the amp probably sounds like crap. Is that the case?

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Posted: Fri Sep 24, 2010 11:16 am
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bluesky636 wrote:
Totally dark? Have you tried swapping tubes or just removing the dark one and reinstalling it?

If the tube is dead, the amp probably sounds like crap. Is that the case?


It's totally dark but I wouldn't say it sounds crap. I haven't swapped them over or taken it out and put it back, I give it a go.


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Posted: Fri Sep 24, 2010 12:16 pm
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Found the problem, the valve looks like it's over heated and blew itself in half.
Is this just a knackered valve or could there be a fault in the amp that could have caused it.

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Post subject: BJr valve concern
Posted: Fri Sep 24, 2010 1:20 pm
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Probably your bias is way too high, which is the norm for BJr. The only solution to prevent tube problems like this in the BJr is to lower the bias considerably. I put an adjustable bias in mine before the tubes were completely shot. :idea:

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Posted: Fri Sep 24, 2010 3:41 pm
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A valve is not intended to light up like a lamp; Some are very red some are dark red.This is due to the fact that the valve emission is at relative low temperature compare to a lamp and this in order to increase life time. However, it should be a little bit red. One test you can do easily is to measure the filament resistor with an ohmmetre between 4 and 5 pins (rougly in the range of the Ohm). If the filament is good and the sound is well, it should be OK; However I agree with shimmilou, if you can install a adjutable bias (there are mods that can be done by tech) it will be better because BJ is well known to have a hot bias. :) (There are also a lot of good valves for replacement (JJ, SED winged C, ... )

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