weird note-specific buzzing and feedback issue with 2000s

[THE COPS]

Yeah, my friend working on it had a similar thought - i think.  I schlepped the whole rig back to my house and tested it out - same exact problem.  I guess we can eliminate location as a contributing factor.  He is going to come hear the sound here tomorrow - and crack it back open. 

Also - just fyi..  i have tried 4ohm, 8ohm, and 16ohm cabs - everything from 412's to 610's.  Same problem.  The only thing that has changed, is the particular note(s) that are affected switched from c to e.  so damn strange.

i will repost when it is solved.

[george]

If you think the problem is the outlet (i.e. utility company) you will need to monitor the voltage, current, frequency, etc over time. Buy yourself a Kill-A-Watt from amazon, etc. This will give you a low budget way to see what is going on with your outlet and look at what your amplifier is drawing from the mains.

Mercury Magnetics has tested several transformers for me in the past if you suspect your PT.

[noel]

Couple things...
First, the AC at your space may well be odd but I've never personally experienced this.  I have heard that some places in the US don't provide very stable or consistent power...but again, I've never experienced that.  The most I can say is that depending on where I've travelled you've got a little more juice in some places.  So what I'm saying is that I'm kind of putting the AC from the wall as low on my list of probably suspects.  Keep it in mind as a possibility but if it is bad wtf can you do unless you own your own power company?

Also, the AC coming out of the wall isn't going to have a "polarity" as your describing it.  The ground makes it all relative.  In the old days there would have been a polarity but then again there were only two prongs so there had to be

As the others have suggested check the obvious but if you do get to the transformers I can recommend a guy in Maine.  Here's a link to his site:
http://members.tripod.com/tubes_tubes_tubes/transformerrewindingservice/index.html

He rewound the output transformer on my 2000s and checked my power transformer.  Its a little on the pricey side and there is a time lag so I'm just warning you to check everything else before spending the time and money.  You'd hate to get them back and realize they're both good 3 weeks and 200 bucks later ya know? 

Hope that helps!
cheers

[Soundmasterg]

There is a difference in the wall with the three wires. Obviously ground has to be ground, and that is usually a green or green/yellow wire in your amp and the cord. Black is usually the hot wire and inside your amp this should be fused and then switched before it gets to the power transformer. White is usually the neutral, and should go directly to the power transformer inside your amp. In 240v setups, white is seperate but in 120v setups, white is usually tied to ground, but that is in your box or at the power station. Sometimes the outlet can be wired with white and black reversed, which can cause some problems, but not the type that are being described so far. It sounds like there is something wrong inside your amp to me.......some troubleshooting has to be done by someone who knows how to work on these amps safely......

Greg

[loudthud]

The trouble could be caused by vibration. This is most likely because to the note specific nature of the problem. When your amp sits on your speaker, it picks up enough vibration to cause the problem. Try moving your amp as far from the speaker cabinet as the speaker cord will allow. Did you say you tried different speaker and instrument cables? Those have to be eliminated as a possible cause.

[THE COPS]

yep - tried all that.  even tried running the head to a different cabinet than the one the head was sitting on.  every guitar i have access to - every cord, every cabinet.  even brought it home and tried everything i have laying around here.  my guy thinks a screen resistor may be in upside down.    he has it now.

[THE COPS]

screen resistor was not in upside down after all.  no idea what it causing this.  amp still with tech.  he is pissed off too. 

anyone have any more ideas?  On top of all that, now it is intermittently not producing sound AT ALL.  this amp worked perfect before I took it to be fixed up. 

[Isaac]

"this amp worked perfect before I took it to be fixed up."

That's usually the biggest clue. What did the tech do who fixed it up?