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Post subject: Odd Blues Junior Issue
Posted: Tue Jun 07, 2011 9:43 am
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Joined: Tue Jun 07, 2011 9:37 am
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Hello everyone, I got a weird problem with my Blues Junior and I was wondering if anyone could shed some knowledge on it. When playing through a clean tone (using the master volume only, keeping "volume" low) everything is great, but when I go to turn up the "volume" control to get more overdrive, I get more overdrive, but I also get this weird doubler effect, where my amp doubles my playing an octave down (usually it's not a perfect octave so it sounds awful, altho occasionally it'll be a perfect octave, giving me a really cool fool in the rain-esque tone haha). Obviously I'm trying to get this fixed, and would like to know what parts to bring in to my tech before hand. The tubes are all glowing normally, and I notice nothing different about them when I crank the volume to get overdrive. Let me know if you have any insight!


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Post subject: Re: Odd Blues Junior Issue
Posted: Tue Jun 07, 2011 11:18 am
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Joined: Tue Jun 29, 2010 1:20 pm
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Hi m_st,

Maybe a rattling or slightly microphonic preamp tube (one of the three small tubes). Try a known good tube in each of the three positions, one at a time, to see if the noise goes away or changes. If you don't have a spare tube, try switching the tubes positions around and see if the noise changes (move the tube in position one to position two, move tube two to position three, and move tube three to position one). It could also be output tube problem, but start with the preamp tubes first. :idea:

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Post subject: Re: Odd Blues Junior Issue
Posted: Tue Jun 07, 2011 3:26 pm
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Joined: Sat Mar 20, 2010 2:30 pm
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Location: A Land Downunder
It could be Phase inverter Oscillation (V3), try swapping the 3 preamp tubes around first as noted above in shimmilou's post.

How old is the amp, is it still in warranty, and when did this problem start?

Also adjusting the lead-dress of the ribbon cables in relation to the back panel can help.

If it's really stubborn and won't go away you should take it to an amp tech and get him to look at the following linked info, the 100pf/500V Silva Mica cap across R30 fixed the PI Oscillation in my amp. But this fix will void the warranty if the warranty is still in effect.

http://billmaudio.com/wp/?page_id=115

Try the preamp tubes first and go from there.

Snowy


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