Hello,
i am building an Aleph 2, and have a problem:
At the moment i power up the amp:
R11 and R12 are burning up in flames.
Q3 breaks, Z5 also.
The rest of the board seems to be ok.
I tested this two times, thought i had a defect Q3 while assembling the board. But it was the same effect.
The schematics (and the part numbers) are the same as in the original Pass documentation. I checked everything about 5 times and can´t see the mistake i made.
My rail voltages are a bit higher than in the originals, i have +-49V instead of the +-45V. Can this 4V more cause the Problem? (I don´t think so)
Now i am absolutely out of ideas what the problem could be and ask you for your help.
I attached my schematics and board layout.
Regards, Martin
i am building an Aleph 2, and have a problem:
At the moment i power up the amp:
R11 and R12 are burning up in flames.
Q3 breaks, Z5 also.
The rest of the board seems to be ok.
I tested this two times, thought i had a defect Q3 while assembling the board. But it was the same effect.
The schematics (and the part numbers) are the same as in the original Pass documentation. I checked everything about 5 times and can´t see the mistake i made.
My rail voltages are a bit higher than in the originals, i have +-49V instead of the +-45V. Can this 4V more cause the Problem? (I don´t think so)
Now i am absolutely out of ideas what the problem could be and ask you for your help.
I attached my schematics and board layout.
Regards, Martin
Pass DIY Addict
Joined 2000
Paid Member
Some parts have pin changes over time - especially if they come from different manufacturers. I was bitten by this on my first amp build. If this is not the case, check your board carefully for inadvertent solder bridges. If you are using an old Aleph-2 board that came from this forum, the solder pads for the small signal transistors are VERY close to one another. Use a fine-tipped flat-blade screwdriver to physically scratch between solder pads when you finish your solder work.
edit - just saw your pcb, so it's not the old one from here, but the advice is still good. Make sure there are no solder bridges. Use a bright light and check carefully.
edit - just saw your pcb, so it's not the old one from here, but the advice is still good. Make sure there are no solder bridges. Use a bright light and check carefully.
Check value of R13
Check that R13 is not shorted out
Check Zener operation before installing new one
Check for shorts on mosfet pads
Test the operation and value of every part before installing them again.
Check that R13 is not shorted out
Check Zener operation before installing new one
Check for shorts on mosfet pads
Test the operation and value of every part before installing them again.
Thank you for your quick answers.
So you think it is not my PCBs or the 49V, but a wrong/defect part or a soldering problem?
Making short circuit somewhere while soldering seems to be unlikely, because the two boards showed exactly the same effect ???
I´ll check again for shorts on the boards.
Regards, Martin
orientation and value is ok. Pic is attached, hope the quality is good enough.
...this is what i think i have done 🙂
Zener was checked in the 2nd try, i THINK there were no shorts.
So you think it is not my PCBs or the 49V, but a wrong/defect part or a soldering problem?
Making short circuit somewhere while soldering seems to be unlikely, because the two boards showed exactly the same effect ???
I´ll check again for shorts on the boards.
Regards, Martin
Attachments
Just out of curiosity for my own knowledge; the board looks fairly damaged from the flames. Is it still cool to use the board?
Those heatsinks can easily get contact with a resistor and short the transistor. There is realy no need for heatsinks on those transistors.
