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one of my mesh plates sparked over the weekend...

208.201.160.2

Posted by Jose R on February 22, 2000 at 10:38:25

In Lucy's voice: "Oh, Ricky...whaaaaaaaaaaaaa!"

Well, my tubes got hit by those evil gremlins...(and I thought I was immune because I have the filaments warmed all the time and am not using a Moth amp)!

When I got home on Friday evening, I abruptly powered on my SE-1 from standby mode and a bluish white spark flared from the lower left-hand corner (where one of the supporting rods is attached to the mesh plate) of one of my AVVT 2A3-C37 Mesh Plates (left-channel) and I heard a slight "pop" from my speaker. I played some music and things sounded fine, so I waited a few minutes to power off into standby again. After waiting a few more minutes I powered the amp back on, this time with a little more careful "flip" of the switch, and the tube did not spark.

Usually, I power on my preamp (Cary SLP-74P) first by turning the knob from standby mode to operate mode and waiting for the 30sec mute switch to audibly click "off;" I then flip the operate switch on the SE-1. On Friday I absentmindedly ignored my usual protocol and abruptly and quickly flipped the operate switch on the amp before the preamp mute switch "clicked" off.

I have turned the amp on and off/into standby (and completely off when I switched drivers) since Friday and through Monday with no incident. I e-mailed Bob at AMR this morning to report my experience and get advise. I will e-mail Kirk at Cary to get his take on this as well later on.

My questions for the tube experts here at the asylum:

Now that we know it is not an amp problem (or at least I'm convinced of that now) what exactly would cause the tube to spark in such a way?

Could it be that this tube is very sensitive to the immediate and quick flow of current after an abrupt start-up, regardless of whether the filaments are kept warm all the time?

Could this be a design issue or is this more likely a production defect?

I am personally treating this as an isolated event and will continue to use the tubes in my amp, but with a continued care during start-up. Again, like I stated above, I have had no sparks since Friday.

Thanks much,

Jose

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