Blue nosed gopher

[skyboltone]

Many of you will recall that I live on a boat and hence do my electronical work in an ocean freight container near SFO. I got this coleman generator with a sine wave looks like this;

http://tinypic.com/view.php?pic=dmz76s&s=3

Anyway, I been fighting this bad bad BUZZ in an Express built with 7189s for a guy. It's got a torroid PT with no center tap. Bridge rectifier. I used hexfreds for the bridge and a suppression cap with a diode to generate the negative bias voltage. It's been interesting.

Anyway, the amp is quiet as a mouse with no guitar plugged in but the minute you do, and the guitar volume is anywhere between 0 and 10 I get this BUZZZZZ. Been fighting it for 5 days. Yanked big hunks a hair out of my beard. Swearing alot. I've torn it apart and put it back together bunches. I've tried all the RFI fixes I can find. No good. Finally today I looked it over one last time, determined it's wired right, closed it up and took it back to the boat with a little Western Electric 4" speaker with a giant magnet. I figured I'd refund the clients deposit and throw it overboard.

So I plug it in at home and bingo, boy genius. It works. Wow.

Daaaaaaaaaammmn. I hate this stuff. Oh, DC is clean. I started with hexfreds and found a little artifact on the DC line. Maybe 5mv? Not much, but not ripple either, just a little squiggle every cycle. Anyway I ripped out the freds and put in 1N4007s but the BUZZ was still there. Seems like the buzz gets going in the PI for some reason. No sign of it in the first two stages........very tiny in the clipper. Tube shields no help.

Anyway here's the conclusion for anyone who cares. I would appreciate some of you smart alecks if you want to make constructive comments in case I'm wrong. Because my other amps with conventional center tapped PTs don't do this, (they do but not nearly as loud) I figure the noise is on the ac ground and just swamps the chassis with that sine wave in the picture up there.

Mat, I gotta clean up some burnt wires and frustration wire routing then I'll get it weighed and give you the final payment amount. You're gonna like this amp. I hate it......only because it beat me half to death building it. Believe it or not it feeds back and makes huge sustain and wonderful harmonics even through a 4" speaker.

[drhulsey]

... I got this coleman generator...

Would a line conditioner on your generator output clear this up? How consistent is the voltage output? An AC voltage regulator, like the Tripp Lite LC series can give you a constant 120V with 87-140V generated input.

[skyboltone]

... I got this coleman generator...

Would a line conditioner on your generator output clear this up? How consistent is the voltage output? An AC voltage regulator, like the Tripp Lite LC series can give you a constant 120V with 87-140V generated input.

I dunno. I fooled with caps on the line in every imaginable combination to no avail. I've been considering a true sine wave invertor and a Optima car battery with a trickle charger. All a guy needs is about 500 watts. The marine ones with built in charger are big bucks though.

[drhulsey]

We always have voltage variation problems with generators on outdoor gigs. The AC voltage regulators will keep your voltage constant, but a line conditioner should help remove unwanted noise. For no more than your needs in the shop, less expensive Furman or Tripp Lite conditioners and regulators should work. I've seen several of the Tripp Lite AC regulators on ebay recently. For example:
http://cgi.ebay.com/TRIPP-LITE-LC-1200a ... dZViewItem

[skyboltone]

We always have voltage variation problems with generators on outdoor gigs. The AC voltage regulators will keep your voltage constant, but a line conditioner should help remove unwanted noise. For no more than your needs in the shop, less expensive Furman or Tripp Lite conditioners and regulators should work. I've seen several of the Tripp Lite AC regulators on ebay recently. For example:
http://cgi.ebay.com/TRIPP-LITE-LC-1200a ... dZViewItem

Thanks Tim. I'll give one a try.

[Abstract]

Mat, I gotta clean up some burnt wires and frustration wire routing then I'll get it weighed and give you the final payment amount. You're gonna like this amp. I hate it......only because it beat me half to death building it. Believe it or not it feeds back and makes huge sustain and wonderful harmonics even through a 4" speaker.

Sounds lovely!

Too bad I don't have any 4" speakers...




Take all the time you need, I'm eager to play it, but I want it to be right.

Dan, you've gone above and beyond here. Thank you, it is appreciated!

[Tubetwang]

if you have a 5 Henri choke laying around...plug that in the same wall outlet...may help clean it up...

[drhulsey]

... I'll give one a try.

Congratulations on your ebay purchase

[skyboltone]

... I'll give one a try.

Congratulations on your ebay purchase

Doncha just hate snipers!

[skyboltone]

if you have a 5 Henri choke laying around...plug that in the same wall outlet...may help clean it up...

It kind of smoothed the ragged edges but the basic waveform remained the same.

Building a LC filter with a series choke and .22uf cap to ground made a beautiful clean waveform but won't pass any current. Not even enough to light up a 40 watt bulb. Well, I guess that's what they're for eh? No passa da AC.

[drhulsey]

... Doncha just hate snipers!

I thought that was the only logical way to act on ebay