harpdude61
1264 posts
Mar 04, 2012
10:37 AM
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I had my first studio time this week and my Double Trouble went sour on me at the worst possible time. &+%&*(#@)!!
I've had the amp 2 1/2 years and before I pay the shipping to and fro with Brian or find a local amp guy that will have it in his shop for weeks on end I thought I would run it by you guys.
In a nutshell the amp was making static like noise. We checked mics, lines, and the amp connections and all seemed well. We put in another pre-amp tube and that was not it. We did not change the big tubes but they both were glowing and heating as normal.
The last thing we did was pull out the mic cable and turned the volume and tone all the way down. Then we took the eraser end of a pencil and tapped very lightly on all tubes, the back of the speakers, parts of the chassis, and the outside of the amp. No matter where we tapped we got the static sound. Sometimes it would hold go on for a couple of seconds.
There are a couple of instrument techs where I work but not sure how much they know about amps.
I appreciate any help.
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Joe_L
1769 posts
Mar 04, 2012
10:43 AM
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I would swap the power tubes, since it's easy to do and not very expensive. They put those things in sockets for a reason. Ease of replacement and likelihood of failure.
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The Blues Photo Gallery
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Kingley
1842 posts
Mar 04, 2012
10:51 AM
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I'd change the power tubes. Other than that I'd email Brian Purdy explaining the problem and ask his advice. Hopefully Mark Burness will read this thread and be able to offer some possible solutions. You could also try posting it over on the Weber amp forum and the Lone Wolf forum too. Someone on those may be able to offer some good advice.
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harpdude61
1266 posts
Mar 04, 2012
11:11 AM
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I was hoping Mark would comment. His advice is always spot on.
So tubes can be glowing and heating and still be bad?
Brian wants me to take out the chassis and ship it to him, but that thing is heavy. I assume I would have to pay shipping both ways and parts if it is tubes....maybe labor?
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5F6H
1089 posts
Mar 04, 2012
11:18 AM
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There are lots of possible causes for static type noises...+1 on Joe & Kingley's suggestion to change the power tubes, probably not essential, but not a bad idea after 2 1/2 years.
Does the amp make the static sound with the preamp tube removed altogether (not just turned down)?
The fact that it relates to physical shock suggests that, if not the power tubes, might be related to a loose ground, like a loose jack socket/volume or tone pot, or a ground tag in the amp's chassis.
DO NOT open up the back of the amp whilst still plugged into wall AC. DO NOT touch any part that isn't directly bolted/screwed to ground/amp chassis (input jack, pots & circuit ground points are). If you can't see anything obviously loose, take it to a tech/send it back to Brian, use a non-conductive probe, like a dry wooden chopstick, to test whether things are loose.
Definitely DO NOT touch the 3 vertical big grey caps at the left of the chassis, or any wires components connected diectly to them, as these hold big voltages even when unplugged from the wall.
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www.myspace.com/markburness
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harpdude61
1267 posts
Mar 04, 2012
11:30 AM
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Thanks Mark. I did switch preamp tubes but I did not try it preamp tube out, but I will shortly.
So I should change power tubes regardless? Is this type tube something I can buy local or do I need to order? Expensive?
Thanks for the safety advice. I did peck on those three caps with the eraser, but the tube was the only thing I touched with my hands and I was unplugged for that.
Mark, Have you started your book yet? Harp Amplification for Dummies. I get the first copy. A belated Happy Birthday to you as well.
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harpdude61
1269 posts
Mar 04, 2012
11:48 AM
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Ok...I tried the pecking around with the preamp tube pulled out and did not get the noise. What does this mean?
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Greg Heumann
1518 posts
Mar 04, 2012
1:12 PM
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What that probably means is that the noise is getting injected from the something in the pre-amp stage. Since swapping the preamp tube didn't change anything, it is more likely a bad solder joint of a component near the preamp tube - including the run from the input jack to the preamp tube. With the amp on, preamp tube plugged in, and being very careful not to touch anything with your hands, use a wood chopstick (safe insulator) and gently poke around on every connection you can find. Even if it makes the noise from poking/rapping at various places, it is likely to get more and more sensitive as you get nearer to the problem. So a combination of this technique and visual inspection should help you find the problem. If you DO find it, resolder the connection - but not before switching off, unplugging and bleeding the capacitors dry of their charge. If you don't know how to do that, it would be a good idea to let an amp tech work on it for you.
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/Greg
Last Edited by on Mar 04, 2012 1:13 PM
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arnenym
41 posts
Mar 04, 2012
1:34 PM
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MORE DO NOT!
DO NOT poke around with a lead pencil! The lead inside it lead the current right up in to your hand!
The electrolytic capacitors could have very high voltages saved in hours after you switched the amp off.
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harpdude61
1270 posts
Mar 04, 2012
3:53 PM
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Thanks Greg and all of you. I'll have some time tomorrow and hopefully nail it down in a SAFE manner.
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