Audio Research Tube AMP Reliability

[I got my VS115 "repaired" from the local ARC service. They told me that the amp is fine, they couldn't find anything. I heard a blast after ca. 250 hours during the warm up period -- I checked the bias and i measured at all tubes 90mA. I also asked ARC about it but they wrote to me a short text "pls. adjust the bias to 65mA". Is there a logical explanation for that ? Ok the amp sounds great but could it happen again? Please advice - thanks for your feedback]

Well your bias difference is odd..What did you mean by "blast". Did a tube arc? Bias can fluctuate depending on your line voltage and the accuracy of your volt meter. BTW its 65 mV not mA as you are measuring across a resistor not in series with the resistor.

I've owned a SP9MkIII pre-amp for 13 years, from new, and the only problem was a rocker switch which failed, needing replacement. Used a variety of 6922s without issues, currently NOS Mullard.

Regarding power amps, had a D70 for a year, and then a D125 for 8 years(both second hand) - in both cases they developed faults which the local (Sydney, Australia)technicians could not fix, despite repeated costly attempts. Loved the sound, especially of the D125, but ownership was frustrating - for the last two years the D125 pretty much sat unused, and old Luxman SS amp filled the gap.

I'm afraid I wouldn't buy another ARC power amp.

That's a shame as the D125 is a very nice sounding amp. Being so far away from the U.S. makes it rather difficult to get parts/service etc.

[ok correct it should be 65mV and the multimeter is not defect, but this is not the point. By "blast" i mean a noisily explosion -- although i was scared i checked the bias and i measured at all tubes 89-90 mV. ]