Tube advice

ARC VT 50, 100 MK I, II and VT200 amps are difficult to bias. If you don't have highly matched tubes it is almost impossible to bias one of these which likely you will if you're lucky only lose a tube and a resistor in the process. If you're not knowledgeable on basic electronics, know how to read a schematic and comfortable with a soldering iron I suggest not tackling one of these amps as you'll likely send it in to ARC to get it fix. The VT100 is a great amp and this is the reason they're on the used market so often, or were several years back. For what it will cost to send a VT100 in to ARC to get retubed and biased by them you couldn't buy a new amp for the money to replace it. If you don't know what you are doing I'd send it in to ARC. 

Dear ADG, Yes, I own a Hickok tube tester, and the number of times it has served me to detect truly defective tubes is near to zero, because such tubes gave away their condition just by listening to them.  It is not that useful for tube matching, either, because it tests all tubes at the same plate voltage and current, which is typically very different from the in-circuit parameters.  Tubes that "match" at one voltage/current setting very often do not match at other settings for voltage, current, grid bias.  Some of the best Hickok testers (e.g., 539B and C) do offer a choice of some of these parameters; those models are to be preferred and are both scarce and very expensive these days.  Further, if you own one, it needs to be calibrated and kept that way.  As an alternative and perhaps to your point, there are available modern tube testers that can actually trace curves.  (I forget the brand and model names, but the internet will tell what they are.) That's the valid way to match tubes. Those are the types used by reputable pros who sell tubes, like Jim McShane and Kevin Deal.  If you want to spend a few thousand bucks on such a tester, that's in a different league from the vintage testers, but are you seriously suggesting that we all need to go out and buy such a device?  

Upscale Audio has a very rigorous tube testing and matching process. Unless you have money to throw away, I’d definitely purchase tubes from Upscale Audio, or Jim McShane. I have more experience with Kevin at Upscale Audio, but Jim McShane also has a top-notch reputation and I’ve received great tubes from both of them as well as Tube Depot. But Upscale clearly has a more rigorous screening process then Tube Depot, that’s for sure. Kevin told me at the Newport show a few weeks ago that he rejects 65% of the Russian tubes he receives as the Russians sell everything they manufacture regardless of how they spec out. Have no fear buying tubes from Upscale or Jim McShane. Btw, I own a ARC VS-55 and I use the hell out of it. It’s a daily driver, and as such, I go through tubes regularly.

I have just got tube amp, AA VSi75 integrated, with KT150 tubes. The tubes are very easy to bias on this model, select the tube number on the display screen and use the thin plastic screw driver through the access hole in front of each tube. Of course I am now planning for tube replacement albeit probably 18 months in the future. I cannot afford to get them from AA as a set of 4 are in the region of $1,500 CND so I will probably go for a matched set from The Tube Store that seems to have a good reputation. And of course we have Upscale which are more expensive than the Tube Store but offers more burn-in and testing which I'm not sure is worth it. Anyway really enjoying the change to tubes from SS. 

ARC's earlier tube amplifiers had a deserved reputation for tube failures and collateral damage that was fixed in later models.
There is a great post over on AK about a D115 that Dave G acquired as a sort of "kit" and built to ARC’s specs. As built under test it had some nasty habits. He carefully modded it to remove all of the nasty habits that would cause failures.Later model amps had all of his mods already incorporated or were redesigned to get rid of those problems.
The last few pages of the post covers all of that and why it was common for the tube amps of that era to fail. Seems there were a lot of "performance" mods that folks were doing that caused the same kind of failures that ARC had experienced. Once it was understood "why", steps were taken to fix the problem.

BillWojo