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Old 31st October 2005, 09:13 PM   #1
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Default Aleph 5 smoking

have just finish the PCB of my Aleph 5 from Kristijan and I have connected them to the power supply.

When I have turned the power the resistor (1 ohm and 221 ohm on the Irfp 244 ( R64-66 and R52-54 on Nelson shematic)) side of -34 volts goes in smoking. You can see on the high resolution picture.

I have checked all soldering and the polarity of the components (ztx 450, Irfp 244, Irf 9610, condensator) and everything looks good. I have checked all the value of all resistors and everything is OK. I'm really dissapointed. Is some people have an idea of the problem ?

On the power supply I use Tr = 2x30 volts 500 VA with 4 x 47000uf on each channel. I have without charge + 41.2 * 0 * -41.2 volts.

Is it possible the voltage was to high. Do you thing I need used 2.2 uH to reduce the voltage or do you know an other possibility to go done the voltage around 34 V.

Could you help me
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Old 31st October 2005, 09:51 PM   #2
Netlist is offline Netlist  Belgium
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Although the voltage is high I am rather suspecting one or more shorted mosfets. Certainly when the 221ohm resistor goes up in smoke. What wattage are your source resistors?

/Hugo
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Old 1st November 2005, 07:08 AM   #3
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I use a 5W 1% to drive the source and a 0.5W 1% for the gate.
I don't invert the GDS connnection on the IFP244. You can see on the picture below.
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Old 1st November 2005, 09:43 AM   #4
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Unless you made a wiring error or a really wrong connection, a smoking gate resistor means a broken mosfet.
A variac and/or a 60 to 100w lightbulb would be real handy to limit the current at initial startup.

/Hugo
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Old 1st November 2005, 06:13 PM   #5
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Hi,

it is very well possible that the fet was already broke when you put it in. You really have to watch for static charges. I always tough the earth connection from the mains before handling the fets. Never broke a IRFP240 but a few IRF610s died while matching.......


William
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Old 1st November 2005, 09:08 PM   #6
Berry is offline Berry  Netherlands
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First measure the voltage over the irf9610. If these are correct connect the irfp outut fets. The voltage is too high for the aleph5, but it will work for a while with a (big)heatsink.
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Old 4th November 2005, 06:38 PM   #7
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You can't believe that.
I'm really a poor guy (If I tell you) stupid, and what you want.
Do you know what is the problem ? Very simple, I have forgoten to put the isolate pad under the IRFP 244. Shameful.

Thank's everybody for your answer. Now everything It's Ok. I will be back in few weeks with the NEW BABY.
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Old 5th November 2005, 12:48 AM   #8
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Glad that you found the error. I love to see some pics from the complete amp.
Success

PS there are more Alpeh5 happily playing around with 40+ DC voltage.
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Old 5th November 2005, 09:34 AM   #9
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Yes, mine! (only just and without load)

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Old 5th November 2005, 05:51 PM   #10
Berry is offline Berry  Netherlands
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Running the Aleph 5 on 40V instead of 34 V , what do i have to change on the PCB ?. And how much power do i have by 4 and 8 ohm speakers ?

Berry
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