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Old 17th November 2011, 05:56 PM   #1
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Default 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 ?
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Old 17th November 2011, 06:55 PM   #2
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is this DIY amps?
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Old 17th November 2011, 08:01 PM   #3
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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...
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Old 17th November 2011, 08:03 PM   #4
Zen Mod is offline Zen Mod  Serbia
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check all solder joints
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Old 17th November 2011, 08:09 PM   #5
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Quote:
Originally Posted by ndhennin View Post
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.
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Old 18th November 2011, 06:04 AM   #6
Gyuri is offline Gyuri  Hungary
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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.)

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Old 18th November 2011, 06:07 AM   #7
h_a is offline h_a  Europe
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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
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Old 18th November 2011, 08:35 AM   #8
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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...
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Old 18th November 2011, 01:46 PM   #9
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Originally Posted by ndhennin View Post
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?
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Old 18th November 2011, 01:54 PM   #10
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Sounds like you've got a dry / cold joint on one or more of the output devices.
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