The making of: The Two Towers (a 25 driver Full Range line array)

I figured to take it easy not to mess anything up. It didn't work though. Almost a year ago I had a heard attack, I've said as much.
Today I'm sure it skipped a few beats. If it's because I'm not as thorough or clear thinking or what not...
I started up everything slowly and step by step. So only the main amplifier feeding the main speakers. Right away the speaker with the 10F's began singing
but I failed to hear the other side. I walked over to that side to see if anything was wrong. As I got there I heard loud puffs and crunch sounds coming from
the (yes, the Telos clone) amplifier. I looked that way and saw flashes, smelled and saw the smoke coming out and rushed over to turn it off. The right (10F)
channel kept playing for a few more seconds before it cut off. Silence and a smell of burned components...

This called for a long walk, as I have quit smoking since what happened almost a year ago and kept thinking: "Nobody's fault but mine". I should have checked
the other side before turning on the amp. The spades that connected the conjugation network seemed to have created a short. I didn't know they could as I
was certain they were protected enough by the shrink wrap. Clearly they were able to though... It probably happened when I replaced a modem behind the
curtain there and had to move the array out of the way. Or something like that... I only remembered that it still worked the last time I hit play.

Not sure what to do or even what to think about it. I'm clearly not as sharp as I was before. Sh#! seems to happen more often. Not always my doing, as I
couldn't have helped what happened to the TC9's. But this? "Nobody's fault but mine"...

P.S. to demonstrate how much patience I actually had... me and my son had ordered parts to make each of us a custom keyboard. While we were at dinner
the doorbel rang. The components for one of them. So before I took the speaker into the house I've been assembling and testing one of the two new
keyboards with my son... His board (he ordered another color) has yet to come but he insisted we try the switches etc. After that he helped me get the
speaker inside and went upstairs while I connected it etc... So I was calm as could be... I really thought I was on top of it all...
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Paid Member
2009-10-13 2:43 am happen.
And it's not always productive to seek for responsability beyond them. To understand why and how it happened is and if possible taking care of conditions for it not to happen again.

Do you have a spare/backup amp Ronald?

You have prooven multiple time how patient you are, and maybe something better will come from this, at least you'll surely learn something while fixing the amp.

Have you open the lid and see what was "burning inside"?

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I still have my old Pioneer a757 Mark II and it's companion, the a400. They may need some service first...
But I also remember being struck by the sound of the Fetzella + arrays... get one of the Pioneers to do the ambience for now...
So there's that option too. Fixing this amp myself? I think this one with 12 Mosfets/channel is a bit above my pay grade ;).


I'm a mechanical engineer, I'm comfortable working with steel (among other things)... mix it with electronics and you'd get sparks, as I've clearly demonstrated...


2011-04-08 5:12 pm
as we get older we have to watch ourselves but this sounds to me like something that could have happened to anybody. That certainly could have happened to me in my youth. I was more impetuous then than I am forgetful now :) Just be glad it was only an amp, which despite the smell, might be restorable. Usually there is some measure of short circuit protection in the output stage if only a sacrificial inductor or sense resistor.
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I've opened up the case and the smell was obvious but I couldn't spot any burned places. It is way beyond my skills so I emailed @koldby to confess my sins.
I'm hoping he'd be willing and have the time to tackle this job. If not I'll have to find a capable person for the job. I'm hesitant to bring it in just anywhere.

Meanwhile I'll make due with what I have on hand. After I'm over the shame of what happened...

I hope I get better at confessing these stupid mistakes. Right now I definitely feel like a fool... Under normal circumstances I'd haul the second array into the
garage but somehow I'm feeling restrained. I guess I'll run some impedance tests on that one first, if only to confirm the former short. That should mean
nothing else is broken on that side. Well, that's about enough of the naked truth I can handle to type here right now...

I'm off singing: I feel stupid, oh so stupid... (think West Side Story music)

Edit: why did I ever decide that confessing every stupid thing I do is a good thing?
I'd feel so much better if I had kept my mouth shut every time I did something stupid like this....
Would have kept my dignity (lol)
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Paid Member
2009-10-13 2:43 am
I don't get you feel ashamed.

I mean: mistake happens, even more when you are doing things... rather than just talk about it!

I must confess i don't get this thing 'to do perfectly at first try'. It doesn't let you learn by doing mistakes, which is the way we all learn things.

Stupidity comes when you repeat over and over the same mistake again and again...

Blowing something along a path to something is just regular thing.

And i think you underestimate your skills Ronald: troubleshooting electronic circuit is easier than you think. Especially when you have people to help around.
Isolating fault isn't this difficult if you have schemo of circuit and a working chanel ( to have voltage references).

And believe me troubleshooting something electronic will bring your selfconfidence back to 100%.

Come on! You fixed some woodworking by using composite materials and the end result is to die for! Why would it be different with some poor transistors, resistance and capacitors? ;)

There is encouraging things in your observation: no residue, ashes,... is good news. Maybe you have been lucky and the only blown things are the output transistors.
Is it dual mono or not? If not there is good news: second chanel is working so we can speculate psu is in good shape ( i hate to have to play too much with psu).
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The amp is a Goldmund Telos 400 clone with 6 pairs of ECX10N20 and ECX10P20 I believe...
@koldby made it some time ago for personal use until I kinda stole it from him :D. I've been in contact with him and
he's willing to help out. It isn't save in the hands of this mechanical engineer ;). Steel and electronics gets you sparks,
you know... I'm quite capable with mechanics, but not versed well enough in trusting myself with electronics. Especially
a jewel like this.
Yes, I've put my nose in the amp to smell lots of burned smells... but I can't locate where it comes from (*). I've send you a schematic.

(*)= if I'm honest, I think the smell come from the side above the output mosfets, not the speaker protection... the left bottom side where
one sees the top 6 mosfets and the PCB above it...

Vandermill internals.jpg

One has to know (or learn) his/her limits :). I can do lots of things, but I'd rather have a knowledgeable person do a job like this.
Even if it costs more sending a 25 KG (net weight) Internationally.


Paid Member
2009-10-13 2:43 am
Thank you, got the schematic.

Very impressive built by Koldby, at first i thought it was a commercial unit you posted initially! I really like the 'plan ground'!

I would not be surprised if mosfets are fryied.

Dual mono could be a bit more problematic as psu capacitors ( or even bridge) might have suffered and i found it to be difficult to identify previously when i faced same kind of issue.

Loudspeaker protection circuit might not protect against some fault conditions.
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