So... my amplifier just exploded!

Soldato
OP
Joined
6 May 2009
Posts
19,886
Although the main caps (purple) on these amps can blow very spectacularly, they also go dead short with no other signs of failure.

Check Q703 and Q702 which are thyristors that are mounted to the heatsinks at the bottom left of your second picture. If a cap is short then one of them is likely to have blown its top off.

Also, as itchy said, check underneath for blown printed circuit track.

Cheers. (at least 1 or 2 good answers in here :) )

I have sent it off for repair earlier but will check the back of the board when its returned to check for brown burn marks and Q703 & Q702.
 
Soldato
Joined
18 Oct 2009
Posts
11,175
Looking at some of the replies, I thought many of them were from a bunch of GD posters. No surprise then to find that the thread was originally posted in GD. I'm just relieved that the people that post here haven't sunk that low, yet.... :p

What surprised me more than the idea of turning on a blown amp, is that the OP thought he would get sensible answers from GD.

Joking aside, hope you get it sorted. :)
 
Soldato
Joined
2 Aug 2012
Posts
7,809
There a place in town I can get it repaired so taking it there in a minute.

Picture of the insides. Nothing looks like its burned out or damaged...

http://i.imgur.com/TiZdgyW.jpg
http://i.imgur.com/YkAfOem.jpg
http://i.imgur.com/lteHXiL.jpg
http://i.imgur.com/MbpmMHe.jpg

If it was me, I would be having a closer look at the small transistor in the top right hand corner of the first image that looks as if its had its back blown off! (Of course, it might just be a trick of the light) and go from there!

I have to say I am disappointed that a high end manufacturer has gone for 85C caps rather than 105C ones but then I guess nothing is built to last any more these days! :(
 
Soldato
Joined
24 Oct 2002
Posts
14,162
Location
Bucks and Edinburgh
Is it me or the two large heat sinks on either side of the amp are doing nothing at all? Normally you would have the large power transistors for the output stage screwed onto the heatsinks but it looks like nothing is attached to them.:confused:
 
Associate
Joined
23 Nov 2004
Posts
301
Is it me or the two large heat sinks on either side of the amp are doing nothing at all? Normally you would have the large power transistors for the output stage screwed onto the heatsinks but it looks like nothing is attached to them.:confused:

The output transistors are bolted to those heatsinks. You can see the mounting bolts along the bottom edge in the photos.
 

Kei

Kei

Soldato
Joined
24 Oct 2008
Posts
2,750
Location
South Wales
10 years isn't old, my Leak 2200 was nearly 40 years old before I decided that it needed a service. (and that used all British made 85 degree capacitors) Most of my amps are past 30 years old.
 
Associate
Joined
17 Mar 2011
Posts
929
Location
Stoke, no, wait, Wilmslow
Yeah some of those caps look very discoloured, like it's been running hot for a while, especially the small blue ones.

The one marked C311 on the far lower left of the first picture looks like it has some blast debris on it and the resistor lead underneath is also discoloured. It may be the case that these parts get more dust depending on where the holes are in the case.

I spotted the possibly skylighted transistor too, but one of those would make a short crack not a loud bang.

I'm assuming the PSU is linear so the transformer itsself may have gone, but it's buried in the corner and we can't see it.
 
Soldato
OP
Joined
6 May 2009
Posts
19,886
Thanks

It was definately a loud bang. It made my ears ring

I initially though it was going to burst into flames but luckily didnt. I was about to run to get a damp towel before unplugging it from the main
 
Caporegime
Joined
1 Nov 2003
Posts
35,691
Location
Lisbon, Portugal
How you would go about putting out an electrical fire (if it was in flames and starting to burn other things nearby too)

Flip the trip switch if it hasnt already gone then by any means necessary.

Ofcourse, this is all easier said than done! Anyone who has actually been in a real fire situation will know just how scary this is.
 
Associate
Joined
17 Mar 2011
Posts
929
Location
Stoke, no, wait, Wilmslow
How you would go about putting out an electrical fire (if it was in flames and starting to burn other things nearby too)

Proper way would be CO2 or a fire blanket. Water/wet things would be bad bad bad.

Generally a fire in an electronic item wouldn't spread because most of the stuff in there would be fire resistant.

We've had a few at work here (I work as a repairer for an industrial electronics company) and whatever blew up just sits there burning but doesn't spread out.

I know there are lots of reports about tumble dryers burning houses down but that's usually because they're full of fluff, keep things clean and you won't have the problem.


I'm at a loss, an ear-ringing bang would usually be powerful enough to spray bits and burn marks all around the inside of the case but I can't see any evidence of it, unless it's one of the hidden main power transistors but i'm speculating again. Let us know what you find out please!
 
Last edited:
Soldato
OP
Joined
6 May 2009
Posts
19,886
I now have it back from repair. It cost £55 and comes with a 3 month warranty
Notes say;

Strip down trace and replace failed output and drive transistors. Setup as required
Resolver dry joints
Rebuild and tested ok.

Will post a couple of pics later on but it works and I am happy as have (proper) music again
 
Associate
Joined
17 Mar 2011
Posts
929
Location
Stoke, no, wait, Wilmslow
Thanks for the update.

That's not a bad price for what was probably a quite time-consuming repair if the thing needed completely stripping down to get at the output drivers.

For example, I do industrial power supplies that take about 4 hours for a complete strip down and overhaul, and we charge £40 per hour. I do change all the 85 caps to 105's though.
 
Back
Top Bottom