ARC VT-50 Damage/Repair Advice

Forgive me in advance, for the very long post. But I am simply copying and pasting, what I posted at another forum...and they suggested I might get some good advice/feedback here.

Here goes:

I need some advice. There's no right or wrong answer; just opinions...though you do have to put yourself in my shoes a bit.

I purchased this used ARC VT-50 tube power-amp; as I am wont to do. You know how I roll: something catches my eye, or I have a need; I buy, I try...and some stuff sticks, and some stuff

Now...this is an "older" unit; point being, it has "manual" biasing. I'm not the world's foremost expert on tube biasing; so before I even unpacked it, or fired it up...I brought the amp into my office...and had some of the "techs" help me with it. We turned it on, waited 15 minutes...and tested the voltage. Left side was stable and spot-on; right side was a little wobbly. So we waited another 45 minutes or so (per should measure at 15 minutes and 1 hour).

At the 15 minute mark, I had the "tech" do I could watch, and make sure there wasn't much to it. You just take your voltmeter leads, and touch them to each side of a test resistor. But at the 1 hour mark...I decided to give it a try. I seems all I did, was touch the 2 voltmeter leads to the test points; just as I had seen the other guy do it. But I must have shaky hands or something...because I got a pop that nearly made me sh*te me pants!

So I shut it down right away, and packed it right back up to be repaired at ARC. It looked to me...the untrained eye...that the damage was minimal; some noticeable burn, down on the tracer circuit...where things arced from the test point. And I talked to the previous owner, and he said he's arc'ed a tracer board before (not necessarily on the same unit); so I didn't feel like a total idiot.

Of course, I was hopeful and optimistic...that the repair, and therefore cost, would be minimal. After all: I had just bought this piece used, to "try out"; and now was having to shell-out for a repair bill...before I even had a chance to hear it, and/or flip it.

I didn't hear from ARC for a spell; so I just dropped them a polite line, to see if they had an update for me. Word came back "technician says unit has extensive PC board damage and will need a tube set. [tech name] is in the process of working up an estimate. Should have more info later in the week”.

Yikes; not, at all, wanted I wanted to hear. I'm especially the need for a new tube set? Describing the incident that occurred; it didn't seem possible I could have blown all 8 tubes!!?? I asked the ARC forum, from another board...if ARC is pretty reputable, for giving it to you straight? Not that I had any doubts. I mean...ARC has been around forever, and I happen to love their kit.

One guy in particular said "they ain't cheap; but...", and I'll paraphrase here...they're not going to rip you off, by padding the bill or claiming unnecessary repairs.

OK, well; with a statement like that...maybe I shouldn't have been surprised. I mean...I was prepared for the "worst", but hopeful for the best. think I'm making this post, if the news turned out to be the latter?

I don't usually get into numbers...but for this discussion; the numbers are important. $1100 is what I was quoted for the repair...AND new set of tubes. Now I get it; a technician at a "reputable" house, like ARC...doesn't want to leave anything to chance. They want to replace ALL damaged parts...go ahead and put in a set of tubes, they KNOW they can trust (even though this incident occurred, when I was biasing the right channel. So even if I blew EVERYTHING on that side...which I wouldn't even bet on; I would be very surprised, if the 2 input tubes and 2 output tubes on the left side, were also "blown"); bias, tune...and send it back to you, knowing it's in tip-top shape.

Out of curiously, I asked the gal who is the admin for the Support department; if she could give me a "line-item" cost, on the tube set. Now again...let me reiterate: ARC...fine, fine company; and their policy and cost, is their policy and cost. I do not post this here to denigrate them; in fact...I usually keep my "dealings" pretty private. But they want $560 for the tubes!

Now...when this amp was on its way; I was already thinking about rolling something into the 6550 slots. Of course, the "best" 6550 known to be going right the Svetlana "Winged" 6550C. But I already had a problem with them of late...and even the guy from Upscale said "smart to stay away"; because evidently, as they were stopping production, they really cut corners on QA at the it's a dice-roll. He recommended Sovtek 6550WE, and even said "that's what ARC is that the Svetlana Cs are out of production". Cost? $32/per; and that's retail, from Upscale! Let me do the math for ya; that's $128, for the Quad...American!!

Now...I don't know what ARC is using in the input slots (4 x 6922s); but I doubt it's anything "exotic". A) "stock" tubes usually aren't, and B) those "tech/engineer" types; they usually don't even think it makes any difference, lol. They often choose, based on reliability; not any audiophile mumbo-jumbo about NOS glass magic, lol. So let's say...they were going to go with something, like the EH Gold Pin? Cost? $25/per; and again...that's retail, and that's at Upscale, etc., etc.

So how can ARC justify charging me, $560; for $228 "worth" of tubes...retail? Well, like I said; they do what they do...and if you want to play the game, which is have them stand 1000% behind the work. You have to pay the price of admission.

So I asked there any way, for them to repair this thing...without the fresh set of tubes? I mean...I understand they need tubes to test it, after repair; but couldn't they use some kind of house "testers", and then send it back tube-less? I mean...this MIGHT end up staying (I actually bought it, because I have a Wyred STP-SE pre-amp...that I think has potential; but needed some warmth, in the way of a tube amp). OTOH...I might just want to sell this thing (as I am again, wont to do).

On top of everything else; I actually already have...(4) 6922s I could use. So I'd cut my repair bill in HALF, and at worst...I'd be looking at ~$130 for a new quad of 6550s. Or...I might just cut bait, sell it advertised as "repaired by ARC; sans owner, roll your own".

Sure...if I bought this new, treasured this amp, and were going to leave it to my kids; I'd let ARC do their thing, and know I had a finely-tuned machine...that I wasn't going to have to turn around and bias again (at least not right away). But this ain't that.

I wasn't even sure ARC would consider it; but I got word today..."Per our technician, you will receive NO SERVICE WARRANTY WHATSOEVER, if you choose this course of action. If the unit is damaged as a result of your tubes, you will be fully responsible for another repair and shipping both ways.” CYA and fear of god accomplished, lol.

I don't know; it's sure cut that repair cost in half (for the record...the full cost of the repair, is damn near what I paid for the amp to begin with!)...get some tubes, AND some HELP! And just very carefully, try to get this thing back in good working order; without losing my shirt.

Now...another suggestion I've been given, is asking ARC if they will repair, and bias; with MY tubes. The 4 existing 6922s I have...and a new Quad of (reputable) 6550s, I would purchase. I think that's an excellent compromise; but IDK. Is that a little like bringing your own steak to a restaurant...and asking them to cook it for you? You know...because their mark-up is too high, lol.

It has also been suggested to me...that it is a SURPRISING amount of damage; to have "slipped" (if that's even what I did) the test resistor.

Trying to make a decision, one way or another, quickly; just feel confused and conflicted about my best course of action. Thanks for any feedback or advice!

^^ So...with the amp off; you clip your leads to the test points. Turn the amp on...let it run-up to operating readiness; and just see what the voltmeter reads?

Wow; not to be ungrateful...but I sure could have used, a simple solution like that a few weeks ago :(

Live and learn.

"08-28-15: Czarivey
One day I brought my Volvo to techie to as how mow will
be to fix my AC. They took a look and told $850 coz I
needed to replace whole compressor and lines as well.
Instead I repaired compressor myself for $15 and saved

I all fairness, you're an auto mechanic.

"Another day I had dropped spinning grinder onto my big
toe and cut it all the way down to the bone. After the
doctor checked he decided to remove the toe. Instead of
going under the blade or saw, I started applying
bacterial ointment that 'eats out' infection and got
myself healed instead of cut."

By the looks of it, so is your doctor.

^^ So...with the amp off; you clip your leads to the test points. Turn the amp on...let it run-up to operating readiness; and just see what the voltmeter reads?

Wow; not to be ungrateful...but I sure could have used, a simple solution like that a few weeks ago :(

Live and learn.
08-28-15: Hiendpawn
Life is not that easy..... You should not be afraid of electricity but you should respect it.

You should remove the top cover with the amp turned off. When biasing is done turn off the amp and wait about 5 minutes for the caps to bleed off before replacing the cover.

I assume you have the plastic adjusting tool for biasing that came with the amp. If not you need to buy one from ARC.

The Amp needs to be powered up to make the adjustments.
The amp needs to be powered up for about 20 minutes, with no signal applied. This allows the amp to stabilize. Next connect the hook on test probes across the bias resistor on one channel. Make sure the hook on probes as well as meter leads do not come into contact with the HOT to the touch 6550 power tubes. Next set the blue adjustment pot to 65 mvdc. You will find it is a lot easier to set the bias having both hands free. As you probably already know it does not take much of a movement of the pot to swing the bias voltage one way or the other. The adjustment pot is quite touchy.

After you get the one channel set to 65 mvdc move the hook on probes of the multimeter to the other channel. Repeat the bias process.

Now go back and check the first channel where you started. You may find you will need to slightly increase the bias voltage again. Next back to the other channel again and check it again. You may have to repeat the process a few times.


When you get the amp back from ARC you will need to install the new tubes. The tubes will be marked and must be installed in the corresponding numbered tube sockets. Leave the top cover off.... Though the Amp was set up and biased by ARC it would be a good idea to check the power tube bias again after a few hours of play time. For one thing the AC line voltage at ARC may not be the same as at your home.

Stop playing music and let the amp stabilize for about 20 minutes or so. Caution! The 6550 tubes will be quite HOT to the touch! Check bias voltage on each channel and readjust if needed.
Zd542 ... no, I am not positive about the time line of the VT-50 production run in light of Jim's (Jea48) post.

My post was based on the ARCDB website: Ordinarily, I find the ARCDB website to be very accurate. That said, Jim (Jea48) said he bought his VT-50 in 1997.

In any case, my main point is that the OP's VT-50 could be a bit long in the tooth. Based on numerous comments I recall reading about the VT series amps, many said they were good. But later models (e.g., the Ref 110 and the VS-115) attracted more enthusiastic reviews and A'gon comments.

FWIW, I previously owned the VS-115 and thought it was a terrific and reliable amp. Easy to maintain too. Shortly after ARC cleared the VS-115 for KT-120 tubes, I dropped in 2 quads. Pretty impressive improvement.

I currently own a Ref 150 SE which uses KT-150 tubes. WOW!!
Out of curiosity, I read the Soundstage review that Jea48 mentioned. Did anyone see this part of the review?

"Frankly, I’m surprised at the quality built into the VT50. This really is engineering and build quality that impresses. An example. I had two VT50s over the review period. The first broke in well and everything was progressing nicely until, in the middle of a quiet listening session, one of the bias-control resistors literally blew apart. The bang was quite loud and accompanied by a flash and smoke, and yet everything shut down cleanly. There was no damage to any ancillary equipment; in fact, except for the fuse and the tube, there was no other damage to amp. The issue was obviously a faulty resistor and not ARC’s doing, but the superb engineering confined the problem and saved my gear."