Smoke on my power amp


I was listening the music with the right speaker wire detached to listen to the left speaker alone. The speaker wire was still attached at the amp side. My preamp does not have the balance knob.
After 20 secs or so, there was a smoke on my power amp.
I quickly turn off the amp.
Once smoke comes, would it be safe to turn it on again? I wonder whether it is permanently damaged.
Is it not safe to listen to the music with the speaker wire detached from one speaker but still attached on the amp side?
My amp is Plinius SA 102.
Any comment?
thx


440fd5f6 4010 4019 bd4e 9968025de619ihcho
Smoke, don’t power up again.smoke, do not power up, unplug and  can McGrath’s for a check up.

.had a Rotel Rb- 1090 stereo amp, a beast w power and headroom., she made my old vega d9’s Sing like no other!

one afternoon I hit the power button, and I noticed a white flash, and a small puff of white smoke.
immediately unplug, the inrush current limiter had taken a dump.
   Less than a year after a 2K$ purchase. Just my luck, the map was amazing.

i moved on.

   Unplug, have the amp looked at, where’s there’s smoke, so,ething is not right.
have a tech check it out. Or send to manufacturer to fix.

smoke=bad
Safe with some, not safe with others. How do you know which one you have? Smoke I guess would be one way...


The old rotel power amps were bust proof, had a few.
Caps the size of beer cans for storage, pump the current with 2 rows of output tranis at 20 amps + per trani, they hardly warmed up.
At 5000 usd thats not on!
That is a monster, but then you guys in the states run monsters!
You can contact Frank Gazzo. He is the U.S. Rep.for Plinius Audio and can help you with authorized service. He's a good guy. Frank at Plinius Audio dot com.
not sue where you are located but in the NYC area I can take a look at it


Sounds like you need service don't use it until a good service person looks at it.Good luck!!
You have a problem that has given you no choice but to pack this amp up and send it on to a reputable service person.Turning it back on makes the possibility of more damage than what has already occurred. Electronics does not repair itself.
Have you opened up and look inside to see any visible damage, swollen electrolytic cap, internal blown fuse, maybe something obvious that may be able to be fixed local. Not a fan of shipping a heavy amp if avoidable. Long ago I had a speaker wire come loose on rev-a McCormack and saw smoke blew a internal fuse and had it fixed local from what I was told it caused damage on the rail.
the first question is "why?".  I have a guess: yo disconnected the speaker wires and they touched, shorting out the amp's "unconnected" channel.  Guess.
IS there permanent damage?  Maybe. Some, yes. Significant? we don;t know without looking. Could be nothing more than heat from an emitter resistor that began cooking. Its not good for it, but it might more or less survive. BTDT in the lab.
But the bottom line is you did something more than you think you did; and the fact that you have to ask, says "take it to someone who can check it out thoroughly".
G
Your power amp is now toast!!
+1 itsjustme. Most solid state amps shouldn't have an issue with no load. 
Dont EVEN turn it on again. It's repair shop time. 

I think what itsjustme said wasexactly what had happened. Feel so dumb.
 I am in Michigan, two hour north of Detroit. About a year ago I had it serviced in Chicago, drove five hours.
I may try there again, or I might it send to Galbo Design. 
It would be $300 both way of shipping and maybe at least $500 for service? I wonder whether it is worth while to fix it. Used price of this amp is around $1500.
Thanks for all your replies.
why....why.....why.....would you even do this is beyond me.

for someone that has been in this hobby for a while, you should know better

now you have to pay to ship the amp both ways ( or drive ) and get it serviced.

you just had this thread recently.....

https://forum.audiogon.com/discussions/should-the-power-be-off-every-time-changing-cables


All I know is that the vast majority of amps I own or have owned have a huge warning in the owner's manual that states not to operate the amp without speakers being hooked up. And I think you now know why. It is NOT safe to operate so don't even think about it...
Most amplifiers have a protection circuit that should prevent damage when the speaker wires are shorted. My Vincent and McIntosh amps both shut off immediately when that happens...Don't ask me how I know....   
Well, I feel so stupid about what I had done.
Anyway, I was trying different preamps, different IC cables, different speaker cables, and different sources (CD/SACD players and phono cartridges). While I was playing around, I got a bit sloppy.
I would still like to have the amp with a built in protection mechanism to prevent such case. It is so harmful to the power amp, but having no built in protection mechanism for $5K amp a decade ago does not sound right.
I cannot find any clear damage from these two inside photos. Any of you see burnt components or circuits? Thanks much.
https://photos.google.com/photo/AF1QipPSt_CM_-03crVgXYW6NBwEgfAXc3eNWuPSAlBJ
https://photos.google.com/photo/AF1QipNIz2uuUz90t-qmUl15mIkIjsxDoqVbj8YsuPLa

Technically, once the blue smoke comes out you need to send it for repair to have the smoke put back in.
Plug your amp to a 'Dim Bulb Tester' to find out if any repair is required.

https://www.youtube.com/watch?v=wRFRwOnLsZI&t=15s
@ihcho The Google Photos links you provided in your last post don’t work, at least for members of the public. I’m not sure how or if photos uploaded to Google Photos can be shared publicly.

If you upload the photos to Google Drive, though, and then select/highlight each of them, one of the icons which will appear at the top of the listing will allow you to create a shareable link.

Regards,
-- Al

first .... there is nothing wrong to run an amp without speakers or only one channel. but disconnect speaker cables from the amp terminals to prevent  speaker wires   accidental short... most new amps has adequate protection , but vintage ones   do not survive .
so you got 2 possibilities... one is the other ends of speaker cables touched each other . or   just bad luck and amp  got fried with no reason whats so ever . now, can you turn on the amp ?preferably not... for one reason  ...to help a repair man. when he opens the unit and turn it on hopefully  the defective part still smokes  and he can easily determine the problem. but  if you continue to press power button the part eventually would stop smoking and if there is no   easily noticeable burn mark  troubleshooting is more  difficult .
My bad.
https://www.flickr.com/photos/[email protected]/49415455691/in/dateposted-public/
https://www.flickr.com/photos/[email protected]/49415663367/in/dateposted-public/

I have not turned it on again since the smoke.
I am trying to find which repair shop to send this amp to.
It looks like there is no place working on Plinius amp in Michigan.
Might try Chicago, or send it to Plinius Repairs in CA.

Again, thanks.
I looked at the photos pretty carefully, and the one thing I see that I’m suspicious about involves two of the output transistors in the right channel, the circuitry for which appears in the left half of the second photo.

At the extreme left of the circuit board you’ll see ten power transistors that are attached to a metal sidewall of the chassis, each of which has three leads (connections) to the circuit board. The lowermost of those transistors is near the bottom left of the photo, and the uppermost of those transistors is near the top left of the photo. Counting from the bottom up, the third and the fourth of those transistors appear to have a grayish blob straddling (and perhaps short-circuiting) the two uppermost of their three connections.

Perhaps a close-up photo of those transistors would provide further insight.

BTW, the two glass fuses in each channel (four total), which are not far from the center of the photo, are "DC rail" fuses, which should provide some degree of protection for the output transistors. But without having a schematic or otherwise being familiar with the details of the design it’s hard to say what "some degree" means.

Good luck. Regards,
-- Al

Agree with almarg you need at schematic to simplify repair it can be done without but you may have to through parts at it that look suspect. If you can find an old school tech in your area that has year of experience trouble shooting you may be able to have it fixed for peanuts. If the 2 or 3 graying transistors or resistors are your problem you could be looking at pocket change in parts. You may laugh but the guy that works on my tube and solid state gear on the side works for the school board fixing media equipment and before that had a television repair business. He began his career in the 60's working at a television station. So finding someone local is possible. I don't think running amp without speaker hook up did it, positive and negative must have crossed, good luck you will get it running again.

Not good :-(

When you say "speaker wire detached", do you mean BOTH the wires were uplugged from the right terminals or only one ?  Is it possible you could have shorted the speaker output ?  Typically, the amps should be protected against speaker shorts but nothing is guaranteed.
You may have to send it to New Zealand....
To illustrate what I was referring to in my previous post, in the first of the following photos I’ve uploaded the two transistors with the grayish blobs straddling two of their leads are shown surrounded by a red rectangle. The second photo is a blowup of that area:

https://www.flickr.com/photos/[email protected]/49419393081/in/dateposted-public/

https://www.flickr.com/photos/[email protected]/49418924433/in/dateposted-public/

Although the limited resolution of the original supplied by the OP makes it hard to tell, I wouldn’t be surprised if those transistors were what smoked.

Regards,
-- Al

@ihcho ,
I did the same thing on my old DNA-1-inadvertantly, of course.
The only thing that happened was that the fuses blew.

I would be surprised that your amp wasn't equally protected.
Did any fuses blow?
Bob
Al, I agree. I see a collector to emitter short from what looks like heat damage. The smoke is from the case melting (concave damage in middle to right).
All I know is that the vast majority of amps I own or have owned have a huge warning in the owner’s manual that states not to operate the amp without speakers being hooked up. And I think you now know why. It is NOT safe to operate so don’t even think about it...
I thought I’d weigh in here. Basically this means the vast majority of your amps are fundamentally unstable. An open circuit is the easiest load on the planet - no current flows -- on the condition that the amp is stable. Inherently stable, not "stable when driving loads we kinda hope are there". It usually means that am amp is not inherently stable, **and** that the speaker load forms part of the feedback loop. Note this is a problem with opamps, and is corrected by either "compensating" it (which has side effects) or operating it only within certain parameters - typically not unity gain. Ive designed dozens of amps of various types (chip based, BJT, FET, valve/tube...), some for myself, some for production, some for others to produce, or derive something from. Every single one was unilaterally stable. Open circuit? Might as well be off. Happy as a clam.
So the above may well be true, but in my opinion its a sad situation. I think I’ll go upstairs, unplug the speakers and turn the volume to 11. Just because I can.
So, in the end read the owners manual. but also wonder why the condition is so. To be totally fair, my stuff has some odd requirements too (so read my manuals!) - mostly because i typically leave certain low-power-draw parts operating 24/7 for a variety of sonic reasons - and without on/off cycles they last longer, not shorter. Odd but true.  I used to tape the fuse to the part of the owners manual with warnings. People woudl call up and say "it wont turn on". Did you read the manual?  Humm? Notice anything?  :-)  G
@itsjustme, thanks for your comment. I would add, though, that in the specific case of tube amps having output transformers it seems pretty well established that such amps should not be operated unloaded while they are processing a signal. The concern being that "inductive kick" occurring in the transformer in that situation may damage the transformer and/or the output tubes. And I suppose the same may apply to the many McIntosh solid state amplifiers which have autoformers at their outputs.

Regards,
-- Al

I also like to point out that without a Zobel-network and output inductor built-in, some direct-coupled output solid state amplifier can becomes unstable and go into oscillation without connected to a load, especially connected to a pair of long speaker cable with open end!
 
This is an example of amplifier schematic featured Zobel and inductor: 

https://www.seventransistorlabs.com/tmoranwms/Circuits_2008/2N6254_Power_Amp.gif
In case of TubeAmps!!! Never allow to run it without speakers connected!!!!
In case of the rest, do not shortcut the speaker cable.
Good amps should have safety measures but lets be honest... most up to 5000$ do not have it.
In case of smoke NEVER POWER SUCH EQUIPMENT unless you are professional. Give it back to pro service.
After all YOU HAVE ONE LIFE and this is electrical device.
This is one of the reason why i finally ended with MCintosh.
Not all savings are savings in time function.
Thx,
Were you smokin' before the amp was smoking?
Thanks for all your replies.
The fuses look OK.
I'm thinking of selling it as it is, or getting it fixed.
This amp is so heavy, and shipping is a nightmare.

In the meanwhile, I have a spare AR amp and a Nakamichi Stasis amp, and will listen to them, and just enjoy music, no more playing around with cables.


I would just try replacing the output transistors myself.
I think you’d be hard pressed to find anything new less than $5K or even more to replace the SA-102. Selling it as is would be a big loss (to you) or perhaps a great gain for someone else who can fix it and enjoy it. Your money your choice.
Where are you located?
Two hours north of Detroit.
If the transistor can be easily replaced, I might try by myself.
Thanks for your comments.
If you can get the parts and want to try it yourself.

After detaching from the heat sink, first cut the leads near the body of the transistor and then desolder/remove one at a time. Use some solder wick to clear the through-holes. 

Cut the new device leads to the same length as those removed and form similar, then solder in place.

Looks real easy to do right from the top.
If the transistor can be easily replaced, I might try by myself.

Here comes another thread.

just spend the money and let those that know how to fix it do it and then you know it’s done right.
in the specific case of tube amps having output transformers
Fair enough!  (But we were talking SS...)  Also that is more an issue of disconnecting while playing, rather than "turn on with no load" - which are quite different.
Ihcho,
Have the transistors been destroyed? It’s really grainy from the photos;

Since many of them are connected in parallel they all experienced significant current ( if actually shorted at output), but due to device tolerances, in the event of a short, the devices and emitter resistor combinations with lowest resistance will go poof the fastest; the emitter resistors on all output transistors of the compromised channel should be checked as well because even small changes there can really affect the distortion profile of the output stage.

If this were my amp and such a thing happened I would probably end up rebuilding the output board; Pain in the ass yes, but then you have a factory speced unit once again.

Did you examine the speaker connectors for evidence of arcing ? Black carbon, deformed metal etc...







In your city of Saginaw there is an excellent technician at Gratiot electronics- he can fix your amp quickly and fairly priced. 
I  have had Tim at Gratiot fix all my amps when needed-including Cary, Grommes, and Plinius (many years ago) Very capable on high end repairs.   
Thanks masaja415,
I did not know about them.
I contacted them yesterday. They seem to work on high end audio gears. It is pretty close to where I live. I will give a try.
Huge saving for me if they can fix it.

I've become unstable simply from reading this thread and there are some signs of smoke although maybe it's steam...I'll unplug.
@riley804, "here comes another thread". Still laughing.
Hook up a pair of test speakers and power it up. I've seen smoke pour from tube amps only to find the paint/coating on a resistor discolored. At this point, what have you to lose?
I brought it to service, and the service tech found a few components got hot, but nothing else. He said those components are not really burnt, and can function OK even after got hot and smoked.
I brought it back home and tested, and indeed it works fine.
Hope that it only burn the paints and did not negatively affect the components.
Thanks all, Al, masaja415, ...

ihcho, I probably missed it, but where was the paint burned, on the capacitor or whatever got hot, on the inside chassis, or the outside chassis?