BIAS TUBES VM220 ARC

Hi Wholesale,

Anything to report re tube switching and/or need for repair? Did Cal help you advance the ball any?

Bruce

My electronic gear is all ARC. Check my system thread. My phono pre is a PH-7. Looking to swap it for a PH-8, which I understand is almost as good as the Ref Phono 2 (not SE).

Obviously, I like ARC equipment, so take what I recommend with a grain of salt. I would stay with ARC for your component gear. Aside from excellent performance and build quality, there's a natural synergy when going all ARC. Just my opinion. Not looking or interested in starting another thread about whose equpment is the best.

Back to the bias question -- you can tell very quickly if you have a bad tube or something else. Just switch the tubes around. If the tube is bad, the bias readings will follow the tube. If something else is going on (e.g., bad bias resister) dropping a known "good" tube into the suspect socket will not help.

ARC amps are pretty robust. I would be surprised if there is a serious problem. Hopefully it will be a bad tube or at worst a bad bias resister.

If you speak with Calvin tell him Bruce from PA sends his regards!

Bifwynne, thanks for getting back to me and offering some good advise. I talked to calvin right before I got your last message. He thought it might be bad tubes, thats why I ordered the new set of tubes, and he said the KT-120 would work GREAT with my VM-220. He said it would really help my vandersteen wood quatros in the lower end, and mid's.

I am puzzled why he did not bring up the point of a bad Bias resisters as a possible problem, I think he assumed it was the tubes. going to call back and ask him for further help. as well as going about replacing the resister.

What do you have as a phono stage? Just started into the vinyl world and bought the nano(clearaudio) for now but wanted to get a better one and thought about Joule/ Modwright/ ARC advise? thanks

I will get back to you after i talk to Calvin again

Thanks Stacy

Wholesale, assuming the VTM and KT-120s are compatable, definitely go the KT-120 route. Check with ARC to confirm compatibility. I dropped them into my VS-115. Major improvement across the board.

Now as far as the possible need for an electronic repair --if a bias resisiter blew, the part costs about a buck. I even bought a few back-up sets just in case. If you know how to do simple repairs, you might be able to eyeball the bias resisters and see if one looks blown. In my case, neither I nor my ARC tech could visually see the faulted resister. The tech used a tester and found the fault in about 5 minutes -- most of the time was spent cracking the amp open.

I would be remiss if I didn't warn you about a serious risk if you crack open the amp. Our amps store potentially lethal amounts of high voltage. If you don't know what you're doing re testing and replacing a defective resister or any other part, DON'T DO IT!

Call Calvin at ARC. He can walk you through a few diagniostic procedures that might help to localize the fault. If as I suspect the problem is a blown bias resister, he can either walk you through the repair or refer you to a local ARC authorized repair tech.

In my case, there's an ARC authorized tech whose shop is near my house. Rather than schlep a 70 lb amp around, he came to my house for a small fee and replaced the faulty resister in about 45 minutes. Afterwards, we shot the breeze and listened to some 70s music for a while. Ya gotta luv ARC.

Bottom line -- don't be cheap or a hero. Call ARC and get some solid advice. Call someone who knows what they're doing. If it's just a bias resister, the fix is a snap!!

Please let us know how you make out.

Best, Bruce

The tube switch did not work, I still show very low readings. in #v1 on one amp and #v2 on other. How do i know if the bias resister is blown? Where do i get them at? and is it easy to do myself. thanks I thought the tubes might be blown, so I order a set (octet) x2 TUNG-SOL KT 120,should i try them first or just replace the resister?

Wholesake, how did you make out with the tube switch? I own an ARC VS-115. Tube switching may help and I hope it does. If not, the problem could be a blown bias resister. I have had to replace bias resisers twice already. Bias resisters often blow if a tube arcs. Please let us know how you make out.

Sounds like a bad or poorly matched tube-set. Try switching the offending pair to the other amp and retry. When all is working well, this should be an easy adjustment.

Hi, sorry for the typing error. Yes i am trying to adjust the pots to read 65 mili-volts. all the other pots i can adjust properly only #v1 and #v2 i get weird readings thanks

I am not familiar with your amp, but what are your trying to measure? Most tube bias are in the mili-volt range. Are you trying to adjust the bias pot to read 65 mv? It sound like you multi-meter is on the wrong setting.