Eros -- Loud 'pop'

[grosen]

Another troubleshooting question for the experts. 

My Eros was up and running for about a week until last weekend when I was listening at moderate volume and heard a really loud 'pop'.  I shut everything down immediately, pulled the Eros out of the system, and played a CD. It looks like the power amp has been damaged: seriously distorted sound in one channel.

I checked the resistances and voltages in the Eros and everything was fine.  I very gingerly put it back in the system (with a healthy amp) and played it for a minute or so at low volume: it sounds perfect as far as I can tell.

So my question is: what was the 'pop', and what I can do to see to it that I never hear it again? It's possible that the problem isn't in the Eros at all: it could be in the power amp that now has a damaged channel.  But that's a solid state Belles 150a that's been running without incident for years, and it would be a real coincidence if it decided to blow up when I put the Eros into the system.  So I'm guessing the problem must be in the Eros somewhere, but I don't know why I can't hear it now.

One possibly relevant detail: The pop occurred a couple of minutes after I had swapped in a 7308 that I had been using in my Seduction for the 6922 that came with the Eros. The 7308 tube appears to be ok -- everything sounds fine now -- so I don't know whether this is relevant. 

[Doc B.]

Quite possible that it was the 7308 that made the pop.

[Paully]

I would be curious, how does a pop from an Eros blow the amplifier?  It would have to be a massive miss function in the Eros to do that kind of damage right?  No way it just goes back to playing.  It seems to me a lot more likely that your amp just blew but will be curious to hear from the experts.

[Doc B.]

I was not trying to troubleshoot another manufacturer's amp from a distance as much as I was offering that old stock tubes can make noises. Whether or not the 7308 actually made the noise, obviously I can't say. Whether or not the amp in question is such that it made the noise itself, I can't say either. All I can offer is that I have not myself experienced any issue with pops coming from an Eros and hurting any other equipment.

[Paully]

And I wasn't trying to trouble shoot the amp either or suggest the Eros was at fault.  Just trying to understand what signal can come from a phono pre that could possibly blow a channel in an amplifier that would still leave the original pre in a functional condition.  Any amp or pre can malfunction, I picture a pop blowing speakers, not blowing a component downstream.  Anyway, hardly matters to me, was just a little curious why the OP would think that a pre upstream could do this and whether it was even a real possibility.

[Paul Birkeland]

It's probably not worth speculating too much until the amp is diagnosed and repaired.

I have had more than one solid state power amp "pop" and break, in my experiences it was usually a faulty capacitor or transistor. 

For an amp from the mid 90's, neither of these issues would be unexpected, it just becomes part of the maintenance of equipment of that age (Bottlehead amps included).

-PB

[grosen]

Thanks, all.  I'll let you know what they tell me when they look at the amp.  I was just wondering whether some sort of glitch in the preamp could cause some sort of intense surge that might damage a downstream component.  I had a similar problem years ago with a similar amp: I accidentally jiggled a power cord on my active crossover with everything powered up, which caused a loud pop that damaged one channel in the amp.  I was wondering whether this could be something similar.  FWIW, the Eros sounds fine now, so I'm perfectly willing to believe that it's just a coincidence.

[Grainger49]

I would expect the output capacitors to protect from DC passing on to the rest of the system, except during startup.  You should startup from source, Eros, to amp with a 10s or longer pause between components.  

Still the coupling cap it will still pass on a thump/pop with some small attenuation.  

I guess the basic question is where the "pop" originated from as well as what caused it.

A number of years ago I had a solid state power amp that cold amplify DC.  One day I had a power outage while I was not home and it amplified the DC into my Dyneaudio woofers.  They were smoked.

[grosen]

So .... I go to box up the amp to ship it off, decide to check it one more time and discover that it has fixed itself.   Which means it was never the amp.  Which means I've got no idea what happened.   I don't really care, of course, as long as it all works.  But I am curious.  If anyone has a theory about self-repairing hi fi equipment, I'd love to hear it. Thanks again for the comments.

[Jim R.]

My experience with self-healing electronic gear is that it is still in need of attention :-).

Check for some loose parts or bad mechanical connections as a first pass.

-- Jim

[Doc B.]

C'mon Jim, where's your sense of adventure (smiley, wink, say no more)