Smoke coming out from my Aleph.... Please HELP!

lscangus · 3rd July 2006, 11:45 AM

Todya, just now, i have powered up my Aleph-X with a vairable transformer, and after about 30 seconds, there are smoke coming out from the output resistor, but when i switch it off, i cannot feel any thing whihc is hot.

And i have notice a strange thing is the cirucit does not draw any power from the -V supply, as when i switch it off, the voltage accross the -V supply doesn't drop. but the +V voltage drops quickly.

Thank you for your kind attention to this thread. This is my first aleph. And i want it to work.. Please help!

Angus

Netlist · 3rd July 2006, 12:44 PM

Angus,
A nice thing to start with is to tell us (link) which schematic you used, what rail voltage, and possible changes you made to the schematic.
I think with output R's you mean from output to ground but it's guesswork for now.

/Hugo

lscangus · 3rd July 2006, 01:11 PM

My Aleph-X compact PCB

This is the board which i am using, i ma uisng a rail voltage of 20V, smoke coming out when it is tested at +-17V. The BIAS current is 6A.

Angus

Netlist · 3rd July 2006, 05:26 PM

Sorry Angus, I can't go into debugging the board to reconstruct the schematic. Also, I need to know exactly what resistors were smoking.

/Hugo

lscangus · 4th July 2006, 01:05 PM

The resistor that is in smoke is the one parallel to the 33ohm resistor, which is in series with the Output.

But i do not understand why it doesn't not draw any current from the -V

eapavant · 4th July 2006, 02:11 PM

If you post a schematic I am sure Netlist and others can help you. With out one there is not much they can do.

eapavant · 4th July 2006, 02:13 PM

I found this in the thread from your GB. It looks like KK's.

lscangus · 4th July 2006, 03:03 PM

Quote:

Originally posted by eapavant
I found this in the thread from your GB. It looks like KK's.

That is the one, thank you for all your help.

Angus

EUVL · 5th July 2006, 06:16 AM

Angus,

Try the following first to see if the diff pair is working / adjusted properly.

Disconnect the power boards completely from your frontend board. Change R3/R53 to 100k. Tie both +ve & -ve inputs to ground. Power up and adjust VR101 until the voltage across R3 & R53 are approx. 3.9V.

If this is OK, you should get about 1A flowing through each of the lower MOSFETs.

I am on trip at the moment. But I am sure other can / will help.

Patrick

lscangus · 5th July 2006, 08:29 AM

How do i know there is a current of 1 A flowing?

Angus

3rd July 2006, 11:45 AM	#1
lscangus diyAudio Member Join Date: Oct 2005	Smoke coming out from my Aleph.... Please HELP! Todya, just now, i have powered up my Aleph-X with a vairable transformer, and after about 30 seconds, there are smoke coming out from the output resistor, but when i switch it off, i cannot feel any thing whihc is hot. And i have notice a strange thing is the cirucit does not draw any power from the -V supply, as when i switch it off, the voltage accross the -V supply doesn't drop. but the +V voltage drops quickly. Thank you for your kind attention to this thread. This is my first aleph. And i want it to work.. Please help! Angus

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3rd July 2006, 12:44 PM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Angus, A nice thing to start with is to tell us (link) which schematic you used, what rail voltage, and possible changes you made to the schematic. I think with output R's you mean from output to ground but it's guesswork for now. /Hugo

3rd July 2006, 01:11 PM	#3
lscangus diyAudio Member Join Date: Oct 2005	My Aleph-X compact PCB This is the board which i am using, i ma uisng a rail voltage of 20V, smoke coming out when it is tested at +-17V. The BIAS current is 6A. Angus

3rd July 2006, 05:26 PM	#4
Netlist diyAudio Moderator Join Date: Jan 2003	Sorry Angus, I can't go into debugging the board to reconstruct the schematic. Also, I need to know exactly what resistors were smoking. /Hugo

4th July 2006, 01:05 PM	#5
lscangus diyAudio Member Join Date: Oct 2005	The resistor that is in smoke is the one parallel to the 33ohm resistor, which is in series with the Output. But i do not understand why it doesn't not draw any current from the -V

4th July 2006, 02:11 PM	#6
eapavant diyAudio Member Join Date: Aug 2005	If you post a schematic I am sure Netlist and others can help you. With out one there is not much they can do.

5th July 2006, 06:16 AM	#9
EUVL diyAudio Member Join Date: Oct 2003	Angus, Try the following first to see if the diff pair is working / adjusted properly. Disconnect the power boards completely from your frontend board. Change R3/R53 to 100k. Tie both +ve & -ve inputs to ground. Power up and adjust VR101 until the voltage across R3 & R53 are approx. 3.9V. If this is OK, you should get about 1A flowing through each of the lower MOSFETs. I am on trip at the moment. But I am sure other can / will help. Patrick

5th July 2006, 08:29 AM	#10
lscangus diyAudio Member Join Date: Oct 2005	How do i know there is a current of 1 A flowing? Angus

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