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Audio Research VS115 - click, snap -did it arc or not?

After many years of just enjoying reading all the knowledgeable posts here I now have a question on how to deal further with this amp. 
What happened? Set it up through the balanced inputs (removing the bridges) and connected Audiostatic ES300 speakers on the 4 ohm tap. Source is a dbx venu360 delivering everything above 100 Hz to the VS115, everything below to the subwoofer/amp. It plays nicely along until suddenly there is a pronounced click or snap, having read about resistors being taken out when tubes go bad on ARC equipment I immediately darted off and yanked the power cord from the outlet. There was no smoke or bad smell, but I let it sit for a couple hours and then proceeded to take of the plate and found nothing burnt on a visual inspect. Next was a simple check of each tube for filament and shorts (checking each possible connection with a mulitmeter it should only return low resistance for 2 and 7 for the KT120 and 4 and 5 for the 6H30). All turned out fine. So now I am wondering what really happened and how to proceed, out of my location sending it to the manufacturer or finding a technician is not my first choice.
Assumption A is that all I heard was the relay (which comes on 5 secs after power on, I couldn't find a reference to it in the manual but would assume it is a plop protection for the speakers) and have to wonder under what conditions it would come off (undervoltage or exceeding current to the speakers)?
Assumption B is that something "went" and needs to be found out. Would you take out the tubes and go part by part and compare value vs. measurement on resistors, caps etc. I do know that in a network values will interact, but a failed component may come up, drawback is the amount of time involved. Alternatively power it up connected but with no signal and measure each bias output (on the back)...all the while ready to yank the power cord immediately.

Cheers
Brxl 
brxl
bifwynne
2,206 posts
 
brxl, ... looks like you sourced the problem.  I suggest that you buy a pair of ARC KT-120s to replace the affect pair, .... after you replace the blown resister(s). 

ARC matched tubes are as good as it gets.  If too expensive, pick up a quad from Upscale Audio and buy the ARC select grade.  Forget the cryo treatment.

Please advise on how you make out.   
brxl OP
21 posts
 
I replaced the resistor and carefully watched the bias, nothing noteworthy so far and it is back playing.
The tubes should have 400 hours on them. I will get a matched pair from tubestore (as that is the source for the other 6 tubes that had no quirks) ...just in case. Also on order 2 matched pairs of Shuguang 6550As to be tried out with the 20 year old ones I already have. 
atmasphere's avatar
atmasphere
11,783 posts
 
Sounds like a tube arced (if you will pardon the expression) and took out the resistor. After some handling of the tubes, the arc is probably temporarily cleared, but I would not be surprised to hear that if the tube were placed back in service that this happened again.


The time on the tube is irrelevant- get it replaced. For best results get a matched pair. ARC does pretty stringent testing so expect to pay a bit more for their tubes, but I would also expect them to hold up better.
brxl OP
21 posts
 
I agree, that is the motivation to replace the two tubes on that pot.
I am interested in your rationale for a different supplier for the pair (ARC vs tubestore), please elaborate.
However if the reason is "pretty stringent testing" shouldn't the next step not be to replace the remaining 3 pairs from tubestore as well (assuming theirs is not as)? 
There is also logistics and finances to be considered, I am located in Canada so any cross border shipment is an extra (in time and money), especially with brokerage fees as personal pick-up and custom declaration is prohibited at the moment.
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