ADA Depot - A Forum To Support Users of ADA Amplification Gear

ADA Preamps => Original MP-1 => Topic started by: j_weeks on June 06, 2014, 02:30:29 PM

Title: MP-1 loud buzz
Post by: j_weeks on June 06, 2014, 02:30:29 PM: I just picked up another MP-1. The unit works fine for the first 1-2 minutes, then after it heats up i start to get a loud buzz/hum. I put new tubes in it and noticed that one of the tube sockets was slightly loose, but both tubes still light up when powered on. Has anyone experienced this problem before?? :???:
Title: Re: MP-1 loud buzz
Post by: j_weeks on June 06, 2014, 02:34:46 PM: Heres a video of what the preamp is doing. https://www.youtube.com/watch?v=tAgtZCMz-UQ
Title: Re: MP-1 loud buzz
Post by: j_weeks on June 06, 2014, 05:27:59 PM: Hell I think I found the problem. One of the caps looks shot.
Title: Re: MP-1 loud buzz
Post by: rnolan on June 07, 2014, 02:38:21 AM: Mmm, it's not looking like a happy cappy, and you may well have located your problem (and hopefully that's all it is)
Title: Re: MP-1 loud buzz
Post by: MarshallJMP on June 07, 2014, 09:12:39 AM: Yes seems to be shot,replace all 3 (black) caps while you're at it.
Title: Re: MP-1 loud buzz
Post by: j_weeks on June 12, 2014, 07:51:39 PM: I replaced all 3 caps on the tube board (6.8 uF 450v) and she's back and running perfect. No more hum :banana:
Title: Re: MP-1 loud buzz
Post by: MarshallJMP on June 13, 2014, 05:22:10 AM: Ok great to hear!!
Title: Re: MP-1 loud buzz
Post by: rnolan on June 13, 2014, 11:43:12 PM: Quote from: j_weeks on June 12, 2014, 07:51:39 PM
I replaced all 3 caps on the tube board (6.8 uF 450v) and she's back and running perfect. No more hum :banana:
:whoohoo!:
Title: Re: MP-1 loud buzz
Post by: gb on July 02, 2014, 03:51:25 PM: So by caps you mean capacitor? And how do you know if they are stuffed by looking at them?
Title: Re: MP-1 loud buzz
Post by: j_weeks on July 02, 2014, 07:52:52 PM: Correct gb. If a capacitor is swollen out on top, or busted open as in the case with my mp-1, it is an obvious sign that the capacitor is no longer viable. That is not always the case though, some bad capacitors show no signs.