Broken A 30

[icewall]

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?

 

[stoN_Cold]

You have the correct channel and compare measurement.

Regards zeoN_Rider

 

[Russellc]

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]

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

 

[HIPCHECK]

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]

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]

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

 

[bobodioulasso]

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

 

[icewall]

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]

So, back from holiday, started measuring. Finds that after R112 where there's supposed to be +15V

An externally hosted image should be here but it was not working when we last tested it.

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?

 

[bobodioulasso]

If i well understand 0v at collector of Q5?
And 24v instead of 15v at R112-R113 junction.
Then R113 is open. (broken). Or bad soldered.

 

[icewall]

Desoldered both resistors and found them ok, them I desoldered the ZTX450 and exchanged it for a brand new one. Finally I have the same value for both channels, gave up and did nothing more. Will try some music tonight, perhaps