Problem with AR Ref 300 Mk II - any experience?

Hi Otto,

The nominal value of the fuse is 250mA/250V (fast type), so i think the fuse with the tin wire seems to be the right, original one. If you take a good look at the metal parts of the fuse you can see the value.
The fuse feeds the 8 output tubes, so if there is something wrong in that cirquit or modificated it is possible that the original fuse of 250 mA will blow-up.

Best Regard, Gert.

Otto, you wrote:

(1) "I already decided to have our local ARC service guy look at the whole amp..."

Me: Good call.

(2) "One question regarding my original V5 tube: when checking it with the right meter on the front panel, it did not reach the green area any more. I tried to adjust it, but even in the "full" position, the meter was not in the green area (but close to). There was no acustic [sic] impact to be heard though. Is this a sign of age of the tube?"

Me: It could be.

(3) "Is it necessary to replace then - or should I wait for any acustic impact before replacing it?"

Me: Absolutely not!! If those tubes are outside the 2000 use marker, as Gary (Hifigeek) said, you are living on borrowed time. The tube's propensity to fail and take out passives (e.g., bias resisters) increases with age.

Otto ... it appears that you are not sure how much time has been racked up on the tubes. I am hesitant to recommend this, but if you have serious doubts about hours of use, replace the tubes as soon as possible.

One more suggestion -- the amp is not that terribly old by ARC standards. Having said that, I find it odd that the amp may have blown other passives like caps, or required some circuit board repairs. I suggest you contact Kalvin Dahl or Chris Ossana (the Service Manager) at ARC and ask them if the local ARC tech should specifically perform certain diagnostics to ascertain whether other parts need to be replaced.

I am also hesitant to suggest my next point, but I would certainly include it in the conversation. If one of the circuit boards looks discolored because of a passive failure, I would ask Kal or Chris whether it would make more sense to simply replace the suspect board.

The Ref 300 is an expensive piece of gear. To sound its best, it should be put into tip-top operating order. That includes fresh tubes if warranted. And as I said above, I would make sure that both amps are thoroughly looked over.

P.S. Did you recently but the Ref 300? If so, I wonder if its worth returning it if that's an option.

The first problem I always see is a customer buys a used ARC amp for a good price and then after a few months the fuses start blowing or outputs start arcing. Moral...No one sells a used ARC amp at a good price with new ARC tubes in it.
The second problem I see is a customer has an ARC amp and is unaware of the elapsed time on the output tubes. One output tube arc and takes a resistor and/or a fuse with it. Customer replaces the tube and weeks later another output tube arcs and causes more damage. Moral....When output tubes start to arc, replace ALL the output tubes. This way, you don't have to worry when the next tube will fail and it's easier to keep track of elapsed tube hours when you replace them all at the same time. I also recommend to my customers that we use ARC tubes. The reason...you don't use cheap gas in a Ferrari.

Thanks to everybody for the valuable input!
I took the amp to out local ARC service center today, and asked them already for the things you suggest (cueck the circuit board, check all tubes,...).

[Because someone asked: I bought the amps 3 years ago, from
a dealer, with warrenty, at a fair but not cheap price.
So I guess this was ok, given that these amps were no
longer available. But I agree that there is always some
incertainty regarding the real hours on the tubes...]

Again: thanks to all of you, your input was valuable, I learnt a lot, and it gave me confidence that I do the right thing (having the amp checked in detail).

Regards,
Otto