Mesa Nomad 45 unbearable hum

[ajisjesus]

somebody help me out here....

so my dad bought a mesa nomad 45 off ebay and when we got it it was fine. Then tone kinda sucked and the 3rd channel (according to my mother) sounded like bacon frying in a pan but after about 2 weeks worth of fiddling we came out with some pretty decent blues and metal tones... so for about a month neither of us used the amp (we had been much to busy.... ) but of course as things go i had been using the amp my dad turned it on and nothing came out... needless to say... he was pissed

after the yelling and blame of who broke the amp subsided we opened it up and discovered that the 7 pin power connector near the back right corner had fried on one of the pins... (if your looking from the front of the board L-R its #3 one of the green wires)

so we called mesa about the problem and the tech there said that this was a design flaw and that it happens often... His suggestion was to solder the wires direct to the leads, so we did and heat shrinked each one to protect against wires touching... and then after putting it back together and flipping both power switches we heard this kinda low hum so we turned up the volume and it got louder... we switched to the solo channel volume and same thing... but we noticed that if we turned the speaker cable upside down and it touched the power amp normal/extreme switch the hum totally went away

so my dad told me to take it apart again and check for any ground wires that may have come loose but there were none... so my dad called back mesa and im not really sure what they said but it sounded like they were stumped

Next step... we totally ripped the board out (which is a serious PITA!!!!!!! ) to get a look up underneath the board... we didnt see any bad joints or anything so i put it totally back together and flipped the switches and this time it was much much much worse!

does anybody have any ideas!?!?!?!?!??!

im at wits end here!!!!!

[Don Moose]

1) Loose chassis ground connection at an input, FX or speaker jack
2) Toasted filter cap - since it's sensitive to which channel is selected, I'm going to vote for one fairly early in the preamp.
3) Missing ground connection between sections - I'm wondering of there's another break in that trace that got fried ... try to follow it around and ohm it out.

... thinking about it a little more, start with number 3.

[ajisjesus]

1) Loose chassis ground connection at an input, FX or speaker jack
2) Toasted filter cap - since it's sensitive to which channel is selected, I'm going to vote for one fairly early in the preamp.
3) Missing ground connection between sections - I'm wondering of there's another break in that trace that got fried ... try to follow it around and ohm it out.

... thinking about it a little more, start with number 3.

1) I forgot to say that after i put it back together the cable touching the regular extreme remedy no longer worked the hum just got much much worse.... but ill take your suggestion im open to anything right now
2) didnt see any thing fried but maybe
3) i dont know why i didnt start with that.... i feel kinda stupid now...

THANKS!!!

[ajisjesus]

ive still got issues.......

[plo]

Hi,

I had the exact same issue myself. I'm not sure if this will help but the thing that stopped the humming for me was to tighten up all the control pots at the front of the cabinet. Sounds silly but might be tied to ground problems or simple noise being added by the movement of the pots.

Just noticed i may have been 4 years too late...sorry