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Old Tubes?


Bbach1

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My Mesa Boogie is my first and only tube amp. I notice quite a bit of hissing noise as of late, expecially when dialing up distortion. I don't remember that noise as being constant. It seems kink of new. Does that signify tubes needing replacement? Anyone have any tube suggestions?

bbach

 

Beauty is in the eye of the beer holder.

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In general, hissing noises are caused by a bad tube or bad capacitors.

 

Is the noise more of a consistant hissing, or a sort of "sizzlig bacon" sound? If the latter, it might be some of the caps in the preamp section.

 

Anyways, remove the "Phase Inverter" ("PI"), or output driver tube- the little "preamp"-sized tube, generally a 12AX7 or 12AT7 or similar tube, closest to the output/power tubes- and see if the hissing stops.

 

If so, replace it with a known good tube. If the noise returns anyways, remove the preamp tubes one at a time, to find out if one or more of them is the culprit, by a process of elimination.

 

If the hissing does NOT stop when you remove the driver/PI-tube, remove or replace the output-tubes, and see if that stops the hissing.

 

If none of the tubes is the cause, then it is likely a capacitor in one of the circuits. You should have the amp checked out by a competant tech familiar with tube-amps in general, and Mesa-Boogies in particular.

 

Best of luck, and post back and tell us how things work out!

Ask yourself- What Would Ren and Stimpy Do?

 

~ Caevan James-Michael Miller-O'Shite ~

_ ___ _ Leprechaun, Esquire _ ___ _

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Thank you for the advice. I am going to mess with it myself as opposed to taking it in for repair. I feel ok about totally screwing something up as long as it is my own. I'm kind of thinking that I want to replace all the tubes because I doubt that has been done for a while. I've had it a year and I've never changed any and I doubt the shop that I bought it from did any unnecessary tube changing. If that does not resolve it, then I will have to get out my electronic testing gear, of which I know very little about, and start messing with it. We'll see how it goes. I like messing with things. I have a 2003 chevy crew cab 4x4 loaded, leather, the works. Got a scrach on the right rear fender in a parking lot and decided to fix it myself. I screwed it up to a point where I had to sand down the entire fender to the metal, then prime, paint, and clear. I spent about two weeks on a job that should have taken one afternoon, but I'll bet you I can do it better the next time. The same will happen with the amp. I'll probably screw it up, but I'll know more about it when I'm done.

bbach

 

Beauty is in the eye of the beer holder.

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Most importantly, DO NOT screw YOURSELF up!

 

Be careful, especially if working with the amp plugged in- EVEN IF IT'S OFF- work with ONE hand; if you have to, tie the other one behind your back, keep it in your pocket, or hold onto a bowl of sand or something that you won't want to drop. Seriously, don't even accidentally rest or brush it against the chassis while doing anything in there; this is to prevent your two limbs from becoming a path to ground, WITH YOUR HEART IN THE MIDDLE.

 

http://www.musicplayer.com/ubb/icons/icon2.gif Even unplugged and turned off, there are potentially LETHAL voltages stored inside your Mesa Boogie. Nothing to be scared of, but definitely deserving respect, as does your own life. O.K.?

 

Get a Sanford "Sharpy" marker; they work great on tube-glass and circuit-boards and chassis and all, and make good non-conductive inspection probes, to boot!

 

Now that I've got all that touched upon, if I can recommend some good books- most especially and in particular, the first one...

 

Check out the following excellent books:

 

http://www.stewmac.com/catalog/images_1sm/1191_1sm.jpg

 

* How To Service Your Own Tube Amp, by Tom Mitchell. (Media Concepts, Norwalk, CA) It can be bought with a companion video- highly recommended. Includes some very useful troubleshooting "flow-charts", mods and tweaking, some schematics, and a lot of useful reference info not always found elsewhere.

 

http://www.stewmac.com/catalog/images_1th/3974_1th.jpg

 

* Inside Tube Amps, by Dan Torres. (Sparpco, Inc. San Mateo, CA) Loads of deep amp info... more than you'll ever use! Includes a step-by-step "build a tube amp from scratch" section that could be a book by itself, and lots of ideas for mods and tweaking. Schematics? The whole damn book is schematics!

 

http://images-eu.amazon.com/images/P/0964106000.01.MZZZZZZZ.jpg

 

* A Desktop Reference of Hip Vintage Guitar Amps, by Gerald Weber. (Kendrick Books, Pflugerville, TX) Some cool tips and tricks for a variety of tweed and blackface favorites, and a lot more. Some sections written by some celebrated amp experts. Lots of schematics.

 

http://www.stewmac.com/catalog/images_1sm/3193_1sm.jpg

 

* The Tube Amp Book, by Aspen Pittman, of Groove Tubes. Has input from our own Myles Rose, among others! Lots of schematics and great info, not to mention drool-inducing pics of... amps! And some guitars, too!

 

Speakin' o' Myles... spend some time perusing his excellent website, and download his Tube Primers, parts one and two. These latter are often updated, as new tubes come and old ones go.

Ask yourself- What Would Ren and Stimpy Do?

 

~ Caevan James-Michael Miller-O'Shite ~

_ ___ _ Leprechaun, Esquire _ ___ _

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Oh excellent my friend. Thank you for the leads. I love learning new stuff. I copied your post to note pad and printed it so I can pursue some of that reading material. Thank you!

bbach

 

Beauty is in the eye of the beer holder.

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You are very welcome!

 

Damn, I musta edited that about five times; double check to see if you've got everything that you want, or just re-copy it now.

 

(I like to use my browser's e-mail "Send Page" function to keep copies of posts and threads that I particularly like; they come out almost exactly as originally displayed.)

 

Just promise me I haven't gotten you to hurt or kill yourself, and to let me- all of us here- know how things go, O.K.? Cool!

Ask yourself- What Would Ren and Stimpy Do?

 

~ Caevan James-Michael Miller-O'Shite ~

_ ___ _ Leprechaun, Esquire _ ___ _

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