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mesa boogie [message #27249] Tue, 14 March 2006 10:33 Go to next message
john is currently offline  john
Messages: 32
Registered: May 2009
Baron
I have a mesa boogie that started cutting out and also making loud intermittent crackling noise. I thought it was the standby switch but repacing that didn't help. My amp repairman replaced the big tubes which helped until I got it back home. I am supposed to try and help the repairman isolate what area the problem is by fooling with the switches when it starts acting up. So far the only time it has acted up again was in the middle of a performance. Now, at home, it sounds nice and sweet again. I read somewhere about re-soldering all the connections. Is this the next step????

Re: mesa boogie [message #27250 is a reply to message #27249] Wed, 15 March 2006 00:17 Go to previous messageGo to next message
Thermionic is currently offline  Thermionic
Messages: 208
Registered: May 2009
Master
The optical switching matrixes are notorious to fail on certain models. They don't usually do just *exactly* as you described, but hey, wild stuff happens sometimes. What model and year is your Mesa?

I doubt if any of the tube socket contacts have lost their tension, but if they have they can cause random, intermittent crackling, especially when the amp is cranked up and subjected to a lot of vibration.

But, the most likely cause is the effects loop jacks, especially if you don't use them much and/or haven't used them in awhile. They are of a certain specific configuration that will jumper the preamp section straight into the power amp section when nothing is plugged into them. With time, their contacts can become tarnished and dirty, and this will cause the amp to intermittently crackle, fizzle, and cut out.

Most of these jacks can be cleaned satisfactorily by pushing a brass-bristle .30 caliber rifle bore brush in and out a few times. However, some types require that you clean them from inside the chassis. It's a simple job and requires nothing more than a piece of 1000 grit sandpaper. Before opening any amp up, always remember that charged filter caps can kill you, even with the amp unplugged. Discharge the filter capacitors by turning the amp off while you're strumming a full E chord at pretty serious volume. Continue strumming until the sound fades completely, 100% away.

Thermionic

mesa boogie [message #27251 is a reply to message #27250] Wed, 15 March 2006 10:23 Go to previous messageGo to next message
john is currently offline  john
Messages: 32
Registered: May 2009
Baron
Thanks Thermionic. I have a Duel Caliber DC3 Mesa Boogie. I think it is around five years old. I will try cleaning the effects loop jack. Before I clean it should I be able to get it to crackle/pop or cut out by wiggling it when I plug something into it?
Thanks for describing the strum method for discharging the filter caps. That sounds easy! I suppose with my luck the only way I will know if this doesn't work will be when I am in the middle of a performance.
Thanks again
John

Re: mesa boogie [message #27254 is a reply to message #27251] Sun, 19 March 2006 21:01 Go to previous messageGo to next message
Thermionic is currently offline  Thermionic
Messages: 208
Registered: May 2009
Master
"Before I clean it should I be able to get it to crackle/pop or cut out by wiggling it when I plug something into it?"

No, plugging something into it will send the signal through a different path than the dirty/tarnished contacts, so that alone won't reveal anything amiss. Just run the brush in and out a few times, and then wait to see if it cuts out again or not. Sometimes, beating heavily on the top of the cabinet (around the center area) with your fist will cause a dirty/tarnished FX loop jack to crackle and pop. The vibration will ever so slightly jarr the contacts and make them crackle as they gain and lose contact intermittently (but sometimes not!).

Without actually pulling the chassis and inspecting stuff, it's a shot in the dark kind of diagnosis. Let us know if it cuts out any more after brushing it out, and we'll go from there.

Thermionic

mesa boogie [message #27255 is a reply to message #27254] Sun, 19 March 2006 22:16 Go to previous messageGo to next message
john is currently offline  john
Messages: 32
Registered: May 2009
Baron
Alright Thermionic, thanks for all the help. Hopefully this will be my last post about my amp.
John

Re: mesa boogie [message #27287 is a reply to message #27255] Sun, 18 June 2006 09:36 Go to previous message
john is currently offline  john
Messages: 32
Registered: May 2009
Baron
It has been about three months since I brushed/cleaned out all the input jacks and it hasn't cut out or crackled since. The boogie has been working great! : )

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