testing a bank of mosfets

Pbassred · 4th December 2007, 09:34 PM

After I reassemble my mosfet amp I'll need to test it. This thing is a mix of K135and J50 - 6 of each. What is the best way to run it up? An Lpad and a speaker? If its not too nieve a question, how do I know that the're all fireing?
Anthing I have'nt thought of?

AndrewT · 5th December 2007, 09:37 AM

After any modification always switch on via a light bulb tester to reduce the damage if there is something wrong.
If all is OK the voltage will come up to around 70% to 90% of direct on line voltage and will allow measurements to be taken.
Once you know that the amp is correctly wired and that the output bias is set to minimum, then remove the tester and switch on again.
Set the bias voltage and measure the individual currents of each of the output devices and of the drivers.

If they are within 10% of each other you are probably OK. But much more likely they will have a current spread approaching 2:1 (highest bias : lowest).

4th December 2007, 09:34 PM	#1
Pbassred diyAudio Member Join Date: Nov 2003 Location: N London	testing a bank of mosfets After I reassemble my mosfet amp I'll need to test it. This thing is a mix of K135and J50 - 6 of each. What is the best way to run it up? An Lpad and a speaker? If its not too nieve a question, how do I know that the're all fireing? Anthing I have'nt thought of? __________________ Jeeees! I only asked https://www.facebook.com/dave.potter.5815

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5th December 2007, 09:37 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	After any modification always switch on via a light bulb tester to reduce the damage if there is something wrong. If all is OK the voltage will come up to around 70% to 90% of direct on line voltage and will allow measurements to be taken. Once you know that the amp is correctly wired and that the output bias is set to minimum, then remove the tester and switch on again. Set the bias voltage and measure the individual currents of each of the output devices and of the drivers. If they are within 10% of each other you are probably OK. But much more likely they will have a current spread approaching 2:1 (highest bias : lowest).