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-   -   Broken A 30 (http://www.diyaudio.com/forums/pass-labs/222782-broken-30-a.html)

icewall 3rd November 2012 09:50 AM

Broken A 30
 
A couple of years ago I build me two Aleph 30, based on boards from chip amp. The miniA but with 6 output devices for use with my Orion setup, top channels. They have been playing great until some weeks ago when one of the channels gave up :( No heat and not much of sound unfortunately! Measuring is not my strong side but after changing q3 on the faulty channel all of my channels where playing happily until the same q3 broke again the other night! :(
Something else has to bee wrong, right, besides the brokenq3? Could someone please point me in the right direction where to start looking?

zeonrider 3rd November 2012 10:16 AM

You have the correct channel and compare measurement.

Regards zeoN_Rider

Russellc 3rd November 2012 02:05 PM

Correct me if wrong original poster, but I think your question is more basic. Is your query more like "yes I have a correct channel, I dont know what to measure to compare?" If so, I find myself in the same boat if one of my channels failed. I am watching this one and am all ears!

Russellc

icewall 3rd November 2012 02:16 PM

@Russelic Yes, exactly what I meant! Couldn't have put it better myself! Thanks ;)

HIPCHECK 3rd November 2012 03:10 PM

1 Attachment(s)
Start by looking at this: pdf by Algar_emi

Also, post, post, post pictures. There might be something that can be found by looking at pictures of your pcb, parts, layout, etc.

Steve

Russellc 3rd November 2012 03:16 PM

Quote:

Originally Posted by HIPCHECK (Post 3226461)
Start by looking at this: pdf by Algar_emi

Also, post, post, post pictures. There might be something that can be found by looking at pictures of your pcb, parts, layout, etc.

Steve

Excellent post! I forgot about it. All I could do without it is look for toasted/discolored parts! If I recall correctly this pic also shows a number of nice things to add, pots to zero off set and a few other things. Thanks for reminding me of it! Helpful for most any Aleph.

Russellc

HIPCHECK 3rd November 2012 03:26 PM

pm me and I can send a few other files if interested.

bobodioulasso 3rd November 2012 06:19 PM

I would replace Z5 zenner which sets the current through Q3. And check for bad solder joint around it.

icewall 6th November 2012 04:29 PM

Thanks for all your input! I'll put it to use as soon as I get home from vacation! Have checked out the PDF and z 5 was one of my suspects ;) initially!

icewall 11th November 2012 02:25 PM

So, back from holiday, started measuring. Finds that after R112 where there's supposed to be +15V http://img.tapatalk.com/d/12/11/11/jaqeza7y.jpg I have same voltage as from V+, 24,5. This can't be right, right? I don't get the 4V that I have on the current source - compared with working channel :) I think my mystery is solved or can something else have broken bescause of this?


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