Selling my SWR SM400S - $400 shipped in Lower 48.
Classic amp.
From SWR Website:
The power amplifiers in the SM-400S can be used individually to provide full biamp capabilities when used with the built-in adjustable electronic crossover or can function as stereo, 250 watt power units. If you need more power, the amps can be bridged for 400 Watts @ 8 ohms or 550 watts @ 4 ohms. The power amps are cooled by a thermostatically controlled fan.
Just had the power transistor replaced. And the Thermostatic fan replaced with a fan that runs all the time. It's a bit louder than the original fan but does a better job
My Friend Vinnie did the work. He took some pics:
https://picasaweb.google.com/1070302...ZUQ&feat=email
Also here is a description from him of the work that was done:
"In a nutshell, the tube plate winding in the xfmr is connected directly to a bridge diode which rectifies the 171volts ac to 250volts dc to power the tube plate circuit. Both hi and low gain inputs utilize the second gain stage of the tube. Only the hi gain utilizes both gain stages. This is why both inputs do not work if the tube or its' circuit fails.
The problem was the interaction between the xfmr and the bridge diode. I cannot determine which component failed first. The xfmr may have failed first, providing a level of voltage that exceeded the diode's input voltage rating. Alternately, the diode may have failed first, shorting its' ac input from the xfmr to ground. The tube circuit is a low-current circuit, 2mA max for both tube stages. The diode is rated for 1A. So the xfmr winding then slowly baked until its' enamel softened, allowing the copper windings to merge, causing lower winding resistance, causing higher current. Eventually the winding burnt itsef open-circuited. There was no ac voltage at all, just more smoking transformer enamel. This sent the xfmr primary current soaring beyond the rating of the 7A & 8A line fuses. This the state the amp was in after it failed. The tube circuit has nothing to do with the power amp or the preamp circuit, so luckily, the power transistors were not taken down in the melee.
So, there is a new xfmr, a new pair of fuses, a new bridge diode, and a new fan. I've left it running with a signal generator and speaker for several hours without any problems. I re-soldered a few wires that were obviously showing signs of wear, mostly from vibration, and removed the layer of soot from the power transistor heatsinks."
One of the rack ears is a little bent.
I'll get some pictures of the actual amp up soon.
Works and sounds great! I've used it on a couple of gigs this summer. But I mostly use my Eden WT800 or go direct with no amp.
