Help bringing up Aleph2. (Smoke)

harvardian · 1st February 2003, 07:15 PM

Hi Guys,

I just finished putting together my Aleph2 and started to bring it up. Smoke!!!

Here is what I did.

1) No inputs
2) No output connected.
3) Variable transformer (10A)

First, I tested the power supply. Brought voltage up slowly, with no driver or output fets connected.

Voltages measured fine +/- 48V (No load)

Connected driver board and output boards.

Brought voltage up slowly. Voltages across R14/R11 were 4.5V

As I ramped up the voltage, everything seemed OK.

As I approached the full +/-45V, smoke poured out of one resistor on each output board...

Any ideas, what other voltages should I look at?

Best Regards,

Dale

xsnailx · 1st February 2003, 08:23 PM

wich one??? on the schematic
seems like not enough wattage

jleaman · 1st February 2003, 08:30 PM

post picture.

harvardian · 1st February 2003, 08:44 PM

More information...

The smoking resistors were the 1.0 Ohm 5W source resistors.

On careful inspection, I have Z4 backwards. Would this cause a problem. I thought it was for transient ESD protection.

Best Regards,

Dale

harvardian · 1st February 2003, 08:50 PM

Seems like I had too much bias current?

jleaman · 1st February 2003, 08:50 PM

picture....

harvardian · 1st February 2003, 08:53 PM

Hi Jason,

Picture of ???

My outputs and driver board are shown here:

Pictures

jleaman · 1st February 2003, 08:56 PM

ahh i see.

fcel · 1st February 2003, 09:00 PM

You have connected the +ve and -ve rail voltage in reverse?

harvardian · 2nd February 2003, 12:06 AM

Guys,

The amp does not go up in smoke right away. I have had the amp at 50% (+/-25V rails) for 30 minutes.

The voltages across the 1 Ohm resistors vary from .43V to .53V

Does this mean that the fets are not sharing current very nicely?

I have
3.7V on the Q1/Q2 Source.
4.5V across R14
4.5V across R11
Q3 Gate is 25-9 = ~16V
Q5 VCE = 3.9V

Gate voltage on the 6 CS output fets is 3.9V
Gate Voltage on the 6 switching fets is -21V

DC offset is <6mV

All look OK?

Bad current sharing? Bad heat sinking?

Thanks,

Dale

1st February 2003, 07:15 PM	#1
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	Help bringing up Aleph2. (Smoke) Hi Guys, I just finished putting together my Aleph2 and started to bring it up. Smoke!!! Here is what I did. 1) No inputs 2) No output connected. 3) Variable transformer (10A) First, I tested the power supply. Brought voltage up slowly, with no driver or output fets connected. Voltages measured fine +/- 48V (No load) Connected driver board and output boards. Brought voltage up slowly. Voltages across R14/R11 were 4.5V As I ramped up the voltage, everything seemed OK. As I approached the full +/-45V, smoke poured out of one resistor on each output board... Any ideas, what other voltages should I look at? Best Regards, Dale __________________ doing my part to Keep Austin Wierd.

1st February 2003, 08:44 PM	#4
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	More information... The smoking resistors were the 1.0 Ohm 5W source resistors. On careful inspection, I have Z4 backwards. Would this cause a problem. I thought it was for transient ESD protection. Best Regards, Dale __________________ doing my part to Keep Austin Wierd.

1st February 2003, 08:50 PM	#5
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	Seems like I had too much bias current? __________________ doing my part to Keep Austin Wierd.

1st February 2003, 08:53 PM	#7
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	Hi Jason, Picture of ??? My outputs and driver board are shown here: Pictures __________________ doing my part to Keep Austin Wierd.

2nd February 2003, 12:06 AM	#10
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	Guys, The amp does not go up in smoke right away. I have had the amp at 50% (+/-25V rails) for 30 minutes. The voltages across the 1 Ohm resistors vary from .43V to .53V Does this mean that the fets are not sharing current very nicely? I have 3.7V on the Q1/Q2 Source. 4.5V across R14 4.5V across R11 Q3 Gate is 25-9 = ~16V Q5 VCE = 3.9V Gate voltage on the 6 CS output fets is 3.9V Gate Voltage on the 6 switching fets is -21V DC offset is <6mV All look OK? Bad current sharing? Bad heat sinking? Thanks, Dale __________________ doing my part to Keep Austin Wierd.


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1st February 2003, 08:23 PM	#2
xsnailx diyAudio Member Join Date: Dec 2002 Location: Poland, Cieszyn	wich one??? on the schematic seems like not enough wattage

1st February 2003, 08:30 PM	#3
jleaman Banned Join Date: Apr 2002	post picture.

1st February 2003, 08:56 PM	#8
jleaman Banned Join Date: Apr 2002	ahh i see.

1st February 2003, 09:00 PM	#9
fcel diyAudio Member Join Date: Sep 2001 Location: LA County	You have connected the +ve and -ve rail voltage in reverse?

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