Second failure of new amplifier


Two weeks ago I burned my new amplifier equipped with eight 6L6 tubes. I had been using the amp for one week before that and everything was OK. The failure occurred when I was switching the amp to the standby position and then to the "off" position (two small tubes and two central power tubes flared, so I switched it off and disconnected from the mains immediately). Switched on - no sound. I found out then that the failure was caused by one damaged 6L6 tube and one burnt fuse.

I replaced the fuse and one tube and everything was OK, until I decided to listen to the music today. I listened to it for 15 minutes, then the same problem occurred - when I was switching it to the standby position and then to the "off" position, there was a clapping sound, one 12AU7 tube ignited (flared strongly) and the tubes do not glow after switching on. I will explore this problem further when I come back from work.

When I was purchasing this amplifier (I would prefer not to disclose the manufacturer), my local dealer claimed that the amp had a "stabilized power supply design" or something like that. One of my audiophile friends dissuaded me from bying this amp, saying that 4 output tubes per channel may cause a problem. The dealer said "don't listen to him - he does not know what a "stabilized design" means."

I think I know now what is "stabilized design" - it's burning fuses and tubes every second day. My dealer is reluctant to take it back even for resale (I suggested that he took it for repair and sold it and only after that give me money), but he claims that the guarantee is void because I replaced the stock tubes (12AU7 and 6922) with my own (vintage)tubes and that I should have waited for a couple of months (while it was burning-in) and should have used it with stock tubes without replacing them for other tubes. He added that according to the European ISO standards, changing the tubes would void the warranty.

My questions are:

1. Does tube-rolling in a new amplifier always void the warranty?
2. Is it true that the auto-bias function (especially when the amp is powered with so many (8!) output tubes is unreliable as compared to manual bias adjustment (like my other amp - Cary SLI-80)?
3. Is it normal when a brand new amplifier behaves like this?

I will appreciate all comments, opinions and suggestions.
transl

Showing 3 responses by cyclonicman

I think your dealer is full of it. I have never heard rolling tubes can void a warranty and if this particular amp will not allow for tube rolling than it should be noted in the warranty or this unscrupulous dealer should have stated it to you. Usually unauthorized modifications or abuse will void the warranty. If possible speak to another amp manufacturer to get an idea of their thoughts on tube rolling in their amps. I know my amp calls for 6550 tubes and I wanted to use KT88's. I called Conrad Johnson and although it wouldn't void my warranty, I was told that I would be unable to bias the KT88's, but that is a far cry from voiding a warranty. I also contacted Cary at one point because I wanted to replace the 6SN7 tubes in my SLP98 preamp with 5692 tubes. The Cary tech told me that it would be no problem and that I would probably like the 5692 tubes very much. This has to work out for you, as you have done nothing wrong. If you cannot get satisfaction from this dealer, then you should contact the better business bureau. Good Luck to you!!
There's a strong possibility that you have made a grey market purchase, so there won't be a warranty from the manufacturer or perhaps your guy is not an authorized dealer, which also would mean that there will be no warranty from the manufacturer, or he is just an unscrupulous person, which seems to be the case!
Timrhu,

I don't think that a defective tube should destroy an amplifier. Even a brand new functioning tube will one day become lifeless and defective. At that point, will it destroy the circuit? I guess it is possible, but it never has happened in my experience. I don't think there are too many threads on this topic either, which would seem like this is a rather unique and unfortunate incident for Transl.
I still don't think he has done anything wrong, except that he purchased this amp from some loser!