Help bringing up Aleph2. (Smoke) - diyAudio
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Old 1st February 2003, 07:15 PM   #1
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Default 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
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Old 1st February 2003, 08:23 PM   #2
xsnailx is offline xsnailx  Poland
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wich one??? on the schematic
seems like not enough wattage
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Old 1st February 2003, 08:30 PM   #3
jleaman is offline jleaman  Belgium
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post picture.
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Old 1st February 2003, 08:44 PM   #4
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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
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Old 1st February 2003, 08:50 PM   #5
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Seems like I had too much bias current?
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Old 1st February 2003, 08:50 PM   #6
jleaman is offline jleaman  Belgium
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picture....
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Old 1st February 2003, 08:53 PM   #7
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Hi Jason,

Picture of ???

My outputs and driver board are shown here:


Pictures
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Old 1st February 2003, 08:56 PM   #8
jleaman is offline jleaman  Belgium
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ahh i see.
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Old 1st February 2003, 09:00 PM   #9
fcel is offline fcel  United States
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You have connected the +ve and -ve rail voltage in reverse?
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Old 2nd February 2003, 12:06 AM   #10
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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
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