SVT Classic Power amp issues

[65ampman]

Yep. It could well be the circuit. Put the arcing tube in a different socket and see if the arc follows the tube or the socket.

Today that tube and all others seem fine. No arcing in any socket. I had already cleaned and retensioned before testing. All tubes measure between 25-29ma at idle when set just below red LED threshold. At 660V B+ this is modest/cool for 6650s. I've seen new Sovteks arc before upon first start up and then settle down and work fine for a normal lifespan. Some kind of impurity inside leftover from the manufacturing process maybe?

[nevetslab]

Any experience with this model or similar 300W tube amp to know normal idle current? 2.5A seems high to me but I dont have another to compare.

With the power tubes all running around 23mA plate current @ idle, they draw about 2.2A/220W @ 120VAC. All of the SVT-CL's have ferrite beads in the plate circuit. On the SVT-VR, it has 5 ohm 5W plate resistors, and NO ferrite beads.

When pushed all the way to clipping, the peak current is considerably higher than your variac ammeter shows.



The average current is, of course, considerably less. The two burst waveforms shown, one being 40Hz Sine-Random, driven into periodic clipping into 4 ohm dummy load, with the other under 4-cycle 40hz Burst followed by 1.9 sec of -20dB signal below that (into 4 ohm spkr), you can see the peak AC mains current measured with a current probe. The last image shows Averaged mains current/wattage/mains Voltage under the sine-random signal drive, periodic clipping.

SVT-CL's behave the same way.

[The Dude]

The amp that came in to me was not an SVT-CL, it was an SVT-VR, sorry. If it helps, it's drawing 1.75 amps at idle.