Problem with AR Ref 300 Mk II - any experience?

Otto, you mused, "I wonder if a bad tube can cause this (assuming that the replacement tube I purchased at ebay is bad - despite its detailled description)." The answer is yes. If a tube arc'ed it can take out passives such as bias resisters. An old cap can also flames out too.

You also querried whether "the amp had an old problem (I recognised some fixed circuit paths on the V5-V8 circuit board) [which is] responsible for this." Could be. That's why I renew my suggestion that you have a training tech look the amp over. In fact both amps.

Even better, I would line up an ARC authorized tech to look the amps over. If you need help locating an ARC authorized tech, call Kal at ARC. He can help

Typo -- was in a rush. The penultimate sentence in the second paragraph should read "That's why I renew my suggestion that you have a [skilled] tech look the amp over."

Hi Bifwynne,

thank you for your input! I already decided to have our local ARC service guy look at the whole amp...
[in fact: a few days after having bought the amps, the other one has had a problem, and I had it checked completely then].

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 impact to be heard though.
Is this a sign of age of the tube?
Is it necessary to replace then - or should I wait for any acustic impact before replacing it?

Again, thank you very much,
best regards,
Otto

Output tube can go at any time. Tubes last approx. 2000 hours in ARC equipment. After that it's like Russian Roulette.

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.