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GK MB150 buzz


wriggers
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Hi all

I'm new to the site and new to bass playing. I have a Gallien Kruger mb150 combo which has developed a buzz at medium to high volumes, buzzier on some notes more than others. The buzz all but disappears if preesure is applied to the side panel. I thought perhaps that there was a loose screw or two causing the panel to vibrate but they were all tight, apart from one at the top right which has a stripped thread presumably from a previous owner. With all the screws out the panel refuses to come off. Are they glued on/sealed in some way? Is there a component attached to this panel (right hand side as you look at the front of the amp) which may be loose. Does anyone have any ideas, I would be grateful for any responses?

Thanks in anticipation

Paul

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Does the buzz get louder as you turn up the amp? Is it present if a bass isn't plugged in? Is it there if your bass is plugged in but you're not making any noise?

I'd give Polar Audio a call, they'll know best. :) [url="http://www.polaraudio.co.uk/"]http://www.polaraudio.co.uk/[/url] the phone number's at the bottom.

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[quote name='ThomBassmonkey' post='1181111' date='Mar 29 2011, 05:09 PM']Does the buzz get louder as you turn up the amp? Is it present if a bass isn't plugged in? Is it there if your bass is plugged in but you're not making any noise?

I'd give Polar Audio a call, they'll know best. :) [url="http://www.polaraudio.co.uk/"]http://www.polaraudio.co.uk/[/url] the phone number's at the bottom.[/quote]

There is normal amp noise but this is more like a rattle when playing at med to high volume as though something is or has worked loose.

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[quote name='icastle' post='1181118' date='Mar 29 2011, 05:12 PM']Try unscrewing the two screws that hold the top handle in place - looking at pics of the combo and the stand alone amp head I suspect that those two screws may go through the combo casing and into the amp chassis.[/quote]


I'll try that tomorrow, but it seems to me that there is something loose which is making the buzz against the side panel. Thanks for quick response.

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If touching the side panel stops the vibration and there's nothing obviously loose externally then I'd be inclined to slide the amp chassis out just a little and try again (keeping you fingers out of the amp of course!).

I had a similar issue on a combo many years ago and ended up fixing it by pushing a scrap of foam between the amp chassis and the casing before screwing it back together.

It's all a bit hit and miss I'm afraid as it's mechanical instead of electronic noise.

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  • 13 years later...

A bit late on the topic but just in case anyone has the same problem. My MB started making a loud rattle at some frequencies back on a gig. This was about 15 years ago. Tried to fix it at the time to no avail. Up in the attic it went, into the section marked "crap".

 

Time passes and I've learnt a bit more about fixing things in the intervening years. Decided yesterday to see it it could be saved. Trying it out, traced the rattle to the rear panel - it was vibrating, but it stopped if I applied pressure to the panel. Opened it up. Behind the speaker GK had mounted a rubber amp foot on a post screwed into the rear panel, topped off with silicone, presumably to deaden the vibes. This rested against  the speaker magnet. The solution seemed to be that if I could increase the "push" of the speaker on the foot/post, it would transmit this to the rear panel and stiffen it with outward pressure so it wouldn't rattle.

 

Off to Screwfix, got a rubber tap washer about 5mm thick to use as a shim between the speaker and the bracing post. Remounted the speaker,which obviously was now a much tighter fit. Plugged in and voila! No rattle.

 

Job done, amp returned to service. If only I'd had the wit 15 years ago. Never mind, feeling very Moneysupermarket.

 

PS pretty certain the silicone is useless - tried it back in the day, but being soft it did nothing.

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