mark 3 "middle" knob issue

[zach.king]

Hi,

I just bought a mark 3 blue stripe combo. It's a 60 watt combo with graphic eq and a c90 speaker.

Tonight was the first time, since I bought it on Saturday, that I have been able to really turn the amp up and play with the settings. But I have one problem that is making me want to take the amp back and find another one.

As I turn the middle eq knob in lead mode I get a loud popping and it actually hums when its turned all the way down to zero. Also at this setting I get a lot of muddy gain and squealing. I've tried replacing tubes one by one but I can't seem to find a solution on my own. It doesn't do this with any other knob on the amp and it's definitely not that "dirty scratchy pot" sound. It's worse. Like I said there's only noise as you move it, but at zero it has the weird hissy, muddy gain, feedback thing going on.

Weird.

Any advice? I had contemplated sending it to boogie for service before this started happening, but this has me worried since I just bought it.

 

[carlosasi]

Well the amp is over 20 years old and probably needs a good going over by the fine folks at Boogie. I'm not sure what is causing the EQ Slider to make noise, but they can probably fix it as well as replace the filter caps or any other necessary maintenance required after that many years of service. This is one of the all time great amps it is worth having it fixed.

 

[zach.king]

Well the amp is over 20 years old and probably needs a good going over by the fine folks at Boogie. I'm not sure what is causing the EQ Slider to make noise, but they can probably fix it as well as replace the filter caps or any other necessary maintenance required after that many years of service. This is one of the all time great amps it is worth having it fixed.

It's not the graphic eq, its the middle knob that you turn. I would think it needs servicing as well. I think I should at least get some money back from the guy I bought it from to fund shipping the amp to boogie to have them go over it and repair anything.

 

[carlosasi]

Seems reasonable if he didn't mention it when selling it to you. You might just need to use contact cleaner on that knob. I know you don't want to spray anything into the EQ Sliders because it would breakdown the grease used for lubrication of the sliders, but it might be ok to use it on the Middle rotary knob. It could be dirt has built up. Anyway I still think its worth a trip to Boogie, I'm thinking of sending mine in shortly. I have a few clicks and pops occurring which I think is a sign the Filter Caps are getting old.