[rollo]

  Heater Board fried. Why ?   Tube did not fail, however oversized fuse was found. An 8amp fuse was in place of a 5amp fuse. The power trannie and output trannie fried.
   I am saving the name of the component at this time to protect them until they respond. Any clues ? HELP !!!


charles

[SET Man]

....however oversized fuse was found. An 8amp fuse was in place of a 5amp fuse. The power trannie and output trannie fried.
.... Any clues ? HELP !!!


charles

Hey!

    Hmmm.... look like a job for Scoopy Doo here. 

Take care,
Buddy

[sts9fan]

Great. Another mystery amp thread.

[poseidonsvoice]

Great. Another mystery amp thread.

Anand.

[rollo]

  It is a Opera Cyber 211 amp. According to the distibutor 211 and 845 based SET amps WILL fry the trannie if tube shorts or fails. Is this so ? Doesn't make sense to me. Am I off base ? Anyone else have an issue with TJ Meshplate 211s ? Or with Trannies frying ?
     Thanks for the input. I am beside myself with this issue. First a power cap exploded now the trannies fried and the IEC melted.
    Other than a faulty tube or short in the trannie does anyone have a clue as to why this might have occurred ? I'm baffled. The importer is helping me out with a very fair price for new trannies. However I am not sure if it will happen again. The fuse holder indicates a 5A fuse. An 8A fuse was factory installed. Although the holder and owners manual indicates 5A the manf. insists that the 8A is correct. Is that a concern ? HELP!!!


charles

[Niteshade]

8 amps is VERY high! Thy the 5 amp. Get a fast blow. If that fails, get the slow blow and work your way up if necessary. It might be worth while to install a fuse in the B+ line. The filament wires and grid wires are long. One of them can let go, unravel and cause a bad short.

[rollo]

Thanks for the advice Bill. Thought the 8A was high as well. I was told by the importer that most if not all 211,845 based designs will burn out the trannie if the tube fails or a short occurs. Is that so  ? If yes the addition of a B+ rail fuse would be the safety feature ? Thanks in advance.


charles

[Norman Tracy]

So to recap:
"The power trannie and output trannie fried."
                     &
"I was told by the importer that most if not all 211,845 based designs will burn out the trannie if the tube fails or a short occurs."

So the importer's position is that in an expensive allegedly high-end tube amp where by their very nature each and every time it is used the tubes are slowing wearing out while operating at very high voltages that it is perfectly normal that the two most expensive components in the device are burned out when the normal wear item reaches end of life.

That is freaking incredible.

I would no more accept that answer than if my electrician told me it was normal for smoke to pour out of my wall switches while they burn up every time a light bulb in a connected lamp burns out.

Competent electrical engineering allows for the normal wear and degradation of the used components in a device over its entire service life. In the case of a high-end audio component in my book that design life should be 25+ years. When tubes are used the fact they wear out and can/will fail in service HAS to be allowed for.  When tubes are used in 2010 the fact the tube factories in China and elsewhere have, shall we say ‘good days and bad days’ when it comes to quality control HAS to be allowed for. All it takes is a fuse in the B+ and heater power busses and some tiny spec of manufacturing quality control to get the right values installed in the fuse holder on the production line. An electrical engineering student’s first try could accomplish a fuse based protection scheme. One would hope the experienced graduate engineering tasked with a high end amp design could come up with something even more reliable and user friendly than blown fuses.

The importer is full of crap, push back hard. The amp should be fixed for free with improved protection circuits installed.

[Niteshade]

I know why they said an 8a fuse would work well: Directly heated cathode RF tubes have a very high inrush current to the filament when it is cold. As the filament heats up, current demand decreases and becomes steady. This high inrush current is also stressful on the filament and can cause metal fatigue and failure. It does not happen very often. They're typically suspended well and made for that kind of stress. On top of the filament inrush current there are charging caps. If yours is SS rectified, the charging caps will demand a high amount of initial current.

Still, it is better to use a small fuse and replace them once in a while. I would have to say that your iron should not have been taken out- but it is likely seeing that around 800 volts was shorted to ground and that will weaken and possibly destroy the main filter caps. A small fuse in the B+ should be taken into consideration. I am guessing even a 250ma (1/4 amp) fast blow fuse should help matters. The company knows inrush current problems exist. Perhaps an inrush current limiter would be a good idea plus the B+ fuse. The main fuse could probably be reduced to 4 amps (fast blow) with inrush control.

Thanks for the advice Bill. Thought the 8A was high as well. I was told by the importer that most if not all 211,845 based designs will burn out the trannie if the tube fails or a short occurs. Is that so  ? If yes the addition of a B+ rail fuse would be the safety feature ? Thanks in advance.


charles

[rollo]

 Norman and Bill your input is invaluable to me. thanks. Bill, yes a SS rectification. I forgot this comment from thje distributor. " why don't you call Carey to find out what they do for protection" That one sent me over the cliff. 
   The distributor is trying to help however it appears the factory is unwilling to take responsibility so far.We shall see. Thanks again for the input guys.


charles

[S Clark]

Admittedly, I know absolutely practically nothing about tube amp design.  Regardless, I'm stunned that a manufacturer states that the loss of a tube will result in a burned out transformer  .  I think I'd sell it and look for another brand.  There are just too many good tube amps out there to choose from to accept that kind of engineering. 

[rollo]

   Its a tough loss to accept. A boat anchor might be a good use eh. Just need a boat.


charles

[StereoNut]

How 'bout a doorstop?

SN

[Mike B.]

I really doubt the fuse value had any effect on this meltdown. This was a catastrophic failure. The time between a 8 and 5 amp fuse blowing would have been a fraction of a second.  I would place the blame on design and component quality. Sorry for your loss

[StereoNut]

How 'bout a doorstop?

All fooling aside, Charles.  I too am sooooo sorry to hear about your amps. If it were me, I'd be on my way to China to ....   

Uh, nevermind - this is a public forum, so no violence! 

Problems like this are why I've been too "chicken" to make the jump from SS to tubes.

SN

[srb]

Thanks for the advice Bill.

Norman and Bill your input is invaluable to me.

Who is this Bill you keep referring to?  Do you mean Blair (Nightshade)?
 
Steve
 
 

[rollo]

 
Who is this Bill you keep referring to?  Do you mean Blair (Nightshade)?
 
Steve

  Yes my mistake. Thanks BLAIR.


charles