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Joined:
January 2006
Posts: 5881
Location: Colorado Rocky Mountains | My faithful Genz Benz amp has crapped out and I’m chasing down an authorized service center for repair. This is a Shenandoah Acoustic Pro, their top shelf acoustic amp of about five years ago which I bought new. It has been my favorite acoustic amp since I bought it and I’ve used it about six hours a week since then. I figure it has 1200 to 1500 hours on it. A few months ago, it just quit. I couldn’t get any sound from it. I checked both channels, with and without the tube preamp on, but nothing. If I cranked up the volume, I could get some fuzz and hiss, but obviously no amplified signal. So I moved it back home and set it up in my bandroom to check it out some more, whereupon it began working correctly again, for maybe a month. It has since conked out again. This time its going to the repair shop once we make contact. I hope it will be an easy fix and that something has simply worn out. Although it still looks brand new, it has a lot of hours of use, so it wouldn’t surprise me if somnething is worn out. Maybe it’s the preamp tube, but it still lights up bright blue as it always has. Hopefully this story will have a happy ending. The amp has been a terrific addition to my live rig. |
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Joined:
January 2009
Posts: 1249
Location: Texas | Prof...lol.
I had the very SAME problem.
ALB NM was the closest GB Auth Dealer (5 hours). So, road trip, right? Plugged it in, in the living room so that my boy could hear my predicament and he looked at me like I was crazy. Worked perfectly until the day I sold it....which was the next day...not really...about 6 months later. I just wrote it off, as I couldnt come up with any logical reason. |
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Joined:
December 2001
Posts: 7222
Location: The Great Pacific Northwest | I have worked on electronics for too many years to think about. 80%+ of failures of pre-computer gear is PHYSICAL not ELECTRONIC. If no longer under Warranty I would open it, and just re-seat everything that plugs into something else. If it comes on, then you know you have some sort of corrosion issue somewhere and likely any decent electronics repair shop can clean it up for you. |
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Joined:
January 2009
Posts: 4535
Location: Flahdaw | I would take the amp for another car ride....should fix it right up. |
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Joined:
January 2006
Posts: 1118
Location: NW Washington State | I'd do what Miles suggests. Lots of connectors wiggle loose and can be reseated just by wiggling them some more and pushing them in place. The tube could come loose too.
If you can hear a louder hiss as you crank the volume up, the power amp might be working OK. Maybe the fault is in the preamp section, which is probably near the input jacks.
Funny that the tube lights up blue. Unless it was made with blue glass, they might have put a blue LED under it to make it look cool. So the blue light might not tell you anything about the tube. If it looks like the tube is easy to remove, I can send you another one to try. 12AX7?
-Steve W. |
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Joined:
January 2006
Posts: 5881
Location: Colorado Rocky Mountains | I took Miles' advice and opened it up last night. I discovered that the "blue" tube was nothing more than a blue micro light placed behind the tube so that it created the illumination through the tube when viewed from the front of the amp. Numbfingers, you had that pegged exactly. I also fired it back up with the chassis outside the cabinet and was able to produce some sound, but it was the classic weak and fragmented sound from a bad tube. There was nothing loose that I could see inside the chassis. Then I replaced the 12AX7 tube with another I had laying around and the sound came back to normal. It was the easiest fix possible. I must remember that tubes wear out. The Genz Acoustic Pro only has one tube, that being in the preamp circuit, and when it goes, it kills the amp. |
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Joined:
March 2005
Posts: 12755
Location: Boise, Idaho | Don't you love it when it's something simple? I couldn't put gas in my car one time and it turned out to be a blown fuse. Who would have thought the vents/evaporative emission systems on newer cars are electric? Blow fuse--vent won't open--closed system--air won't go out--gas won't go in. Why didn't I think of that? |
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Joined:
October 2009
Posts: 133
Location: Ohio | This is the first time I have read this thread. I have a 100 Tube amp that has about 10 tubes in it (off the top of my head) it has 2 12ax7s on each of 3 channels and when I read that your tube was "glowing blue" I was like "well that's your problem" LOL Tubes don't glow blue! |
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Amp Problem