Problem with aleph 2

ndhennin · 17th November 2011, 05:56 PM

Hello,
I suddenly have a problem with one of my aleph 2
Last night, as the amp where turned off, I suddenly heard a loud "ploc", just as if a balloon had just exploded. When I turned on the amps, one of the speakers made a very loud "bzzzzzz". Turned every thing off and had a look inside : nothing looked smoked...took my multimeter and turned on again the amp : looked at the dc offset : 5mv. And suddenly, 40 V !!!!!
Took things appart to search a smoked component and found nothing. Put everything together, measured again the dc output : 5 mv, stable over a long time. Wired to the speaker : good music ! Strange, a bit worried, turned of the amp and went to bed. The day after, turned on the amp : "bzzzzzzzz"...

Does anybody has an idea where it could come from ?

AudioSan · 17th November 2011, 06:55 PM

is this DIY amps?

ndhennin · 17th November 2011, 08:01 PM

You're right, i Forget to mention : yes, those are diy amp. They've been runing fine for 4 years. I recently optimized them (dc offset by à better appairing of thé fets), and It worked fine during a few weeks...

Zen Mod · 17th November 2011, 08:03 PM

check all solder joints

AudioSan · 17th November 2011, 08:09 PM

Quote:

Originally Posted by ndhennin

You're right, i Forget to mention : yes, those are diy amp. They've been runing fine for 4 years. I recently optimized them (dc offset by à better appairing of thé fets), and It worked fine during a few weeks...

do you have pictures and schematics? also for the PSU.

Gyuri · 18th November 2011, 06:04 AM

Do you have a separate psu for each channel?
I have experienced similar phenomenon with my monster aleph on both channel, when one of the four rectifier diodes went to short circuit. (It has a single psu for both channel.)

Gyuri

h_a · 18th November 2011, 06:07 AM

Quote:

when one of the four rectifier diodes went to short circuit.

Schottky diodes ?

Shouldn't happen with standard silicon diodes as these prefer to go open circuit; any case that's a really bad fault - I had that once during testing - and needs a very quick fix.

@ndhennin: I agree with Zen on all accounts, sounds a lot like a cold solder joint to me!

Hannes

ndhennin · 18th November 2011, 08:35 AM

Ok, I am going to check all the solders. But I am still a bit worried about the big "ploc" it made at the beginning : where can this noise come from ? it can not come from a solder point...

AudioSan · 18th November 2011, 01:46 PM

Quote:

Originally Posted by ndhennin

Ok, I am going to check all the solders. But I am still a bit worried about the big "ploc" it made at the beginning : where can this noise come from ? it can not come from a solder point...

yes it can. if your PSU caps is charged. du you have bleeder resistors?

KatieandDad · 18th November 2011, 01:54 PM

Sounds like you've got a dry / cold joint on one or more of the output devices.

17th November 2011, 05:56 PM	#1
ndhennin diyAudio Member Join Date: Apr 2002 Location: Lille (France)	Problem with aleph 2 Hello, I suddenly have a problem with one of my aleph 2 Last night, as the amp where turned off, I suddenly heard a loud "ploc", just as if a balloon had just exploded. When I turned on the amps, one of the speakers made a very loud "bzzzzzz". Turned every thing off and had a look inside : nothing looked smoked...took my multimeter and turned on again the amp : looked at the dc offset : 5mv. And suddenly, 40 V !!!!! Took things appart to search a smoked component and found nothing. Put everything together, measured again the dc output : 5 mv, stable over a long time. Wired to the speaker : good music ! Strange, a bit worried, turned of the amp and went to bed. The day after, turned on the amp : "bzzzzzzzz"... Does anybody has an idea where it could come from ?

17th November 2011, 06:55 PM	#2
AudioSan diyAudio Member Join Date: Feb 2009	is this DIY amps? __________________ soon to be: papa's Class A all the way

17th November 2011, 08:03 PM	#4
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	check all solder joints __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

18th November 2011, 06:04 AM	#6
Gyuri diyAudio Member Join Date: Nov 2003 Location: Budapest	Do you have a separate psu for each channel? I have experienced similar phenomenon with my monster aleph on both channel, when one of the four rectifier diodes went to short circuit. (It has a single psu for both channel.) Gyuri __________________ Those who would have deserved the life they are all dead already. "Oh, my dead dears!" - Captain Cat

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17th November 2011, 08:01 PM	#3
ndhennin diyAudio Member Join Date: Apr 2002 Location: Lille (France)	You're right, i Forget to mention : yes, those are diy amp. They've been runing fine for 4 years. I recently optimized them (dc offset by à better appairing of thé fets), and It worked fine during a few weeks...

18th November 2011, 08:35 AM	#8
ndhennin diyAudio Member Join Date: Apr 2002 Location: Lille (France)	Ok, I am going to check all the solders. But I am still a bit worried about the big "ploc" it made at the beginning : where can this noise come from ? it can not come from a solder point...

18th November 2011, 01:54 PM	#10
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	Sounds like you've got a dry / cold joint on one or more of the output devices.

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