Irfp240 Please Any One!!

jleaman · 7th March 2005, 06:01 AM

Any one got a set of IRFP240's they are willing to donate to me ? i just need 2

Any one ?

Netlist · 7th March 2005, 06:51 AM

Do they have to be matched?

/Hugo

jleaman · 7th March 2005, 06:56 AM

Preferably But maybe closely matched ? my blue amp died some how and now i'm getting rail voltage on the speaker out put. I have to re-bias it and change the out puts witch are 2 devices..

Come to think of it when biasing a amp you have to bias it with a meter on the positive rail in series Right ?

Netlist · 7th March 2005, 07:56 AM

I don't know your amp so I can't comment on the bias setting.
Are you sure the outputs mosfets died?
Drop me a mail where to send them.

/Hugo

quasi · 7th March 2005, 10:36 AM

Most class A/B amplifiers would have fuses in series with the output stage. When setting the bias the fuses must be removed and replaced with suitable resistors. This will protect the output stage in case of a fault. Remember that the fault that blew your FETS could reside anywhere in the cct. If the fault is still there after you replaced the FETS one or both resistors will probably go up in smoke but this is better than smoking FETS.

Using just the multimeter in line with the positive rail will not provide any protection, except maybe the fuse in the meter.

Measuring the voltage across the resistors is an easy way to determine the bias curent (I=V/R).

Typical resistor values would be 50 to 200 ohms @ 1 - 5 watts.

Cheers

jleaman · 7th March 2005, 02:44 PM

I just asked about the biasing it is on the positive rail and in series It should have fuses in these amps * my bad * they do now but also the reason this went up was because i was adjusting the bias pot to make the one fet cooler because one was running hotter than the other for some strange reason.

jleaman · 7th March 2005, 03:17 PM

Thanks for helping me ( netlist )

Netlist · 7th March 2005, 04:05 PM

Make it Postcardware.

/Hugo

jleaman · 7th March 2005, 04:17 PM

Quote:

Originally posted by Netlist
Make it Postcardware.

/Hugo

Post card ? you want a post card ?

Netlist · 7th March 2005, 08:10 PM

Wait till you get the fet's.
But that would be nice, yes.

/Hugo

7th March 2005, 06:01 AM	#1
jleaman Banned Join Date: Apr 2002	Irfp240 Please Any One!! Any one got a set of IRFP240's they are willing to donate to me ? i just need 2 Any one ?

7th March 2005, 10:36 AM	#5
quasi diyAudio Member Join Date: Sep 2004 Location: Adelaide, Australia	Biasing amplifiers Most class A/B amplifiers would have fuses in series with the output stage. When setting the bias the fuses must be removed and replaced with suitable resistors. This will protect the output stage in case of a fault. Remember that the fault that blew your FETS could reside anywhere in the cct. If the fault is still there after you replaced the FETS one or both resistors will probably go up in smoke but this is better than smoking FETS. Using just the multimeter in line with the positive rail will not provide any protection, except maybe the fuse in the meter. Measuring the voltage across the resistors is an easy way to determine the bias curent (I=V/R). Typical resistor values would be 50 to 200 ohms @ 1 - 5 watts. Cheers __________________ http://sites.google.com/site/quasisdiyaudiosite/

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7th March 2005, 06:51 AM	#2
Netlist diyAudio Moderator Join Date: Jan 2003	Do they have to be matched? /Hugo

7th March 2005, 06:56 AM	#3
jleaman Banned Join Date: Apr 2002	Preferably But maybe closely matched ? my blue amp died some how and now i'm getting rail voltage on the speaker out put. I have to re-bias it and change the out puts witch are 2 devices.. Come to think of it when biasing a amp you have to bias it with a meter on the positive rail in series Right ?

7th March 2005, 07:56 AM	#4
Netlist diyAudio Moderator Join Date: Jan 2003	I don't know your amp so I can't comment on the bias setting. Are you sure the outputs mosfets died? Drop me a mail where to send them. /Hugo

7th March 2005, 02:44 PM	#6
jleaman Banned Join Date: Apr 2002	I just asked about the biasing it is on the positive rail and in series It should have fuses in these amps * my bad * they do now but also the reason this went up was because i was adjusting the bias pot to make the one fet cooler because one was running hotter than the other for some strange reason.

7th March 2005, 03:17 PM	#7
jleaman Banned Join Date: Apr 2002	Thanks for helping me ( netlist )

7th March 2005, 04:05 PM	#8
Netlist diyAudio Moderator Join Date: Jan 2003	Make it Postcardware. /Hugo

7th March 2005, 08:10 PM	#10
Netlist diyAudio Moderator Join Date: Jan 2003	Wait till you get the fet's. But that would be nice, yes. /Hugo

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