Problem with aleph 2

[ndhennin]

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]

is this DIY amps?

 

[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...

 

[Zen Mod]

check all solder joints

 

[AudioSan]

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]

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]

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]

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]

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]

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

 

[Gyuri]

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

I'm sorry, I'm not saying it with full conviction that this is the case here.
I'm just saying what happened to me.
Now I've found the diode that was joked with me.
It certainly does not know what he would prefer:
This is a big-big short circuit.
I only know about the diode SILEC RG12, it was in a computer's power supply:
ordinateur Bull GE 115, chr4infb
Another one works.
This is not a Schottky diode presumably.

To be sure, the Aleph buzzed as the god's wrath.
https://skydrive.live.com/?sc=photos&cid=e894cb7d50b65fbf#cid=E894CB7D50B65FBF&id=E894CB7D50B65FBF%21512&sc=photos

I am affraid of it, the details only seen on the big picture.

Wacky

 

[ndhennin]

Verified my solders and found one that could be the cause. Fixed it. Everything working OK since yesterday !
I'll wait a few days before screaming houra ! but thank's for the help.

 

[Thago]

Hi

My Aleph 2 functioned for several years without problems, now suddenly one channel has a large portion of DC on the output terminal. The gain devices remain completely cold, the CCS gets warm.

I already replaced the IRF9610 at the input, a BC546 in the gain devices circuit, a couple of Zener's, and one 220R resistor that looked a bit burned (but it measured completely normal). Has anyone some advice for me (except rebuilding the complete boards)?

 

[Zen Mod]

please forgive me ...... these days my crystal ball is muddy .......

take sch file and measure important voltages and post here

if you don't have handy graphic file , say and I'll post something what you can edit in MS Paint or something similar

 

[Thago]

Hi

Unfortunately, I don't have a file with voltage references, I would be very obliged if you could sent me one.

I have the feeling that something is wrong with the voltages that are supplied to the gain devices. I measured some voltages at the current source board:
DG: 76.4V
DS: 80.5V
DR: 80.8V (R: rail)
GS: 0V
GR: 0V
SR: 0V

The same at the output devices board:
DG: 8.2V
DS: 9.6V
DR: 9.7V
GS: 1.4V
GR: 1.4V
SR: 0.01V

I always thought that the Current Source and Gain Devices boards were mirrors.
There is absolutely no voltage drop over the 1R resistors (DR) at the gain devices board, so no current is flowing there.

Please tell me what other voltages I need to measure, thank you in advance.

 

[Zen Mod]

all relevant voltages are already marked

put file in any graph editor and write down your voltages