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So I recently brought the Opera Consonance M100 back into rotation and replaced the quad of Gold Lion KT77s with new ones. Had almost 2 years trouble free with the old ones that had probably 5000 hours. 

 

The new ones have a few hundred hours on them already. Just turned the amp on to warm up and after a minute or so heard a pop in the left speaker (strange as volume was down to zero) and saw smoke coming out from under the tube. Pulled it immediately. I have put one of the old ones back in its place.

 

Obviously this is not ideal. My question is:

 

Is there any particular issue with using the 3rd odd man out? Should I just put the quad of old ones back in pending replacement? And is there an issue getting a 4th new one that wouldn't have been 'matched' to the other 3 new ones? Could I get a refund or do you just wear it?

 

Thanks for any advice guys :)

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3 minutes ago, lemarquis said:

So I recently brought the Opera Consonance M100 back into rotation and replaced the quad of Gold Lion KT77s with new ones. Had almost 2 years trouble free with the old ones that had probably 5000 hours. 

 

The new ones have a few hundred hours on them already. Just turned the amp on to warm up and after a minute or so heard a pop in the left speaker (strange as volume was down to zero) and saw smoke coming out from under the tube. Pulled it immediately. I have put one of the old ones back in its place.

 

Obviously this is not ideal. My question is:

 

Is there any particular issue with using the 3rd odd man out? Should I just put the quad of old ones back in pending replacement? And is there an issue getting a 4th new one that wouldn't have been 'matched' to the other 3 new ones? Could I get a refund or do you just wear it?

 

Thanks for any advice guys :)

 

 

The issue I see is the smoke.  You have overheated something underneath, and chances are it is now off spec.  You need to get that checked.

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16 minutes ago, aussievintage said:

 

 

The issue I see is the smoke.  You have overheated something underneath, and chances are it is now off spec.  You need to get that checked.

Thanks for the reply. I put an old one back in and it's working fine. The tube that 'blew' looks OK but it rattles if I shake it. Wouldn't that indicate it was a just bad tube? You know much more than I do so happy to accept that, but obviously it would be easier to replace the tube than to get the amp serviced.

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1 minute ago, lemarquis said:

Thanks for the reply. I put an old one back in and it's working fine. The tube that 'blew' looks OK but it rattles if I shake it. Wouldn't that indicate it was a just bad tube? You know much more than I do so happy to accept that, but obviously it would be easier to replace the tube than to get the amp serviced.

 

No, unfortunately.  Tubes don't smoke.  Something else was overheated.  You say it's working fine, but, for example, the bias may be off, if a resistor has changed value due to being overheated.

 

As for the matching all 4 valves, or just replacing one,  well, of course having them matched is best.  otoh if it sounds OK with unmatched valves, then no harm will come from that.

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OK cheers. The unmatched thing is that I have had to put in one of the old 5000 plus hours tubes as a stop gap. I'd consider that very unmatched. I was thinking more of replacing with a new one. Wouldn't be matched to the other three that have maybe 200 hours....

 

Anyway, looks like it will need a looking at :(

 

Thanks for the advice!

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Depending on bias type could be the cathode resistor on that socket smoked.

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11 minutes ago, lemarquis said:

@muon*So even though it still seems to work, it may happen again? Or cause further damage if I keep running it?

Muon's guess has some likelihood, as a faulty valve may short out and that will smoke a cathode resistor

 

As an example, as it is all a guess at this point,  a resistor that's overheated will often go up in value.  So, if it is a cathode bias resistor, that means the bias current the valve(s) will be running at will be a bit lower, so if it was meant to run at, say, 40ma, it could now be 35 or 30 or...  This is, luckily, a non-disastrous result.  You are just running the valves a little "cold", bias wise.

 

However, if you keep using it without really knowing what has happened, then it's a bit of a lottery, IMO.

 

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24 minutes ago, lemarquis said:

@muon*So even though it still seems to work, it may happen again? Or cause further damage if I keep running it?

What aussievintage said above.

 

If something is damaged and smoke likely indicates this, everything may not be cool with it.

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That KT77 might still be alive today if you'd taken my advice and put EH6CA7's in the M100. 🙃

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1 minute ago, deanB said:

That KT77 might still be alive today if you'd taken my advice and put EH6CA7's in the M100. 🙃

Don't blame the Russians B)

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Posted (edited)

It's a Chinese/Russian/Long Island, NYC conspiracy.

Edited by deanB
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5 minutes ago, deanB said:

It's a Chinese/Russian/Long Island, NY conspiracy.

Watching too much Fox News again.

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6 minutes ago, lemarquis said:

Watching too much Fox News again.

Ouch!

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On 26/05/2020 at 5:14 PM, Decky said:

You should buy some spare smoke and put it back in. 

 

I have bucket loads of that stuff. I used to repair Masuda TVs, they were a copius source of spare smoke.

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If smoke appeared from any piece of gear, I wouldn't even power it up til it had been checked over properly and diagnosed/repaired.

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On 28/05/2020 at 7:13 AM, Grizzly said:

If smoke appeared from any piece of gear, I wouldn't even power it up til it had been checked over properly and diagnosed/repaired.

Exactly right as @Grizzly and others have said.

Something has fried (probably a biasing resistor) and the amp needs to be checked otherwise more damage could be done.

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26 minutes ago, Sierra said:

Exactly right as @Grizzly and others have said.

Something has fried (probably a biasing resistor) and the amp needs to be checked otherwise more damage could be done.

Thanks @Sierra  I did power it up again with a replacement tube for 5 minutes and it was working but after the advice received here I took it out of rotation pending a check up. The previous owner also replaced a resistor apparently. Speculation of course, but is it relatively common for those things to fry? It may be a simple fix (just want a heads up so I don't get fleeced on repairs).

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Guest jakeyb77
On 28/05/2020 at 7:13 AM, Grizzly said:

If smoke appeared from any piece of gear, I wouldn't even power it up til it had been checked over properly and diagnosed/repaired.

Boring! 🙄

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I shorted speaker wires on a Meridian mono block while hungover, switched on followed by magic puff of white smoke!

Looked on in disbelief,  got bigger cloud of white smoke then sparks!

Never played that amp again! 😬

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4 minutes ago, evil c said:

I shorted speaker wires on a Meridian mono block while hungover, switched on followed by magic puff of white smoke!

Looked on in disbelief,  got bigger cloud of white smoke then sparks!

Never played that amp again! 😬

I am truly sorry for your loss :( 

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Posted (edited)
11 minutes ago, lemarquis said:

I am truly sorry for your loss :( 

It actually was the catalyst behind revitalizing my audio journey setting me on a new path! 😄

 

In fact happened again several years later, funnily enough with another Meridian amp - and again undaunted I ended up on a new adventure indulging in even better gear!

Just adds to the whole experience.  😉

 

Edit: should add I bought a Valve amplifier that sounded flat, got it tested and 1 - KT88 tube had blown.

Spare set I received had 3 of 4 tubes blown!!

 

So got whole set of 4 replaced with new tubes - and sold the amp to be safe.

 

Edited by evil c
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