Xtant 403A output fets

brandes.cm · 27th March 2010, 03:10 PM

The output fets in the mono channel are IRF530 and IRF9530. What is a good replacement for these? Will the "N" variety work, otherwise Fairchild has a FQP17P10 and FQP13N10. The fairchild parts are called a direct cross!!

The other channels are using IRF530 and IRFz34's. With other amps I haven't noticed much issue with using Fairchild parts.

I believe this amp is made by Mitek, which also makes MTX amps. The build quality is spot on, I like that.

cory

Perry Babin · 27th March 2010, 04:13 PM

The outputs in this amp shouldn't be critical. If you have the FQP outputs, try them but test it thoroughly (including confirming that the bias current doesn't drift when near thermal). If I had to choose substitute outputs, I'd likely use the IRF540 (or IRF540a) and IRF9540.

I don't know if this amp is like the 603 and 604 but if it is, the quality isn't that great (in my opinion). It's not going to fall apart but they run components (in the 603and 604) so hot that they'll damage the board. The damage is obvious on amps that have been used for an extended period of time. It may not be as severe on this amp due to the lower rail voltage.

If you have time, try this. Let the amp idle for ~3-4 minutes and set the DC offset. Let it continue to idle and confirm that the DC offset has held. Switch the amp off and let it cool for 10-15 minutes. Power it back up and check the DC offset again. What's the DC offset ~15 seconds after powering it up from a cold start?

brandes.cm · 27th March 2010, 04:28 PM

Once I get replacement parts I will give it a go.

The power supply fets physically burnt up, no damage to the board at all. It had 60ne06-16 placed. I replaced those with RFP50n06, the supply seems to be ok.

My observation was based on solder quality, no flux residue and sm components placed value up. If the design is marginal I could have a polished turd on my hands!

brandes.cm · 29th March 2010, 03:44 AM

So I replaced all the outputs with a combination FQP33n10 and SFP9540. Idle current has been steady at 1 amp warm and cold. I measure this using a .005 ohm resistor inline with B+.

Power numbers unloaded are 18.5Vrms front channels and 25.5Vrms rear/mono channel. I will throw my 3 ohm load on them and get a feel for real power output.

cory

27th March 2010, 03:10 PM	#1
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Xtant 403A output fets The output fets in the mono channel are IRF530 and IRF9530. What is a good replacement for these? Will the "N" variety work, otherwise Fairchild has a FQP17P10 and FQP13N10. The fairchild parts are called a direct cross!! The other channels are using IRF530 and IRFz34's. With other amps I haven't noticed much issue with using Fairchild parts. I believe this amp is made by Mitek, which also makes MTX amps. The build quality is spot on, I like that. cory

27th March 2010, 04:13 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The outputs in this amp shouldn't be critical. If you have the FQP outputs, try them but test it thoroughly (including confirming that the bias current doesn't drift when near thermal). If I had to choose substitute outputs, I'd likely use the IRF540 (or IRF540a) and IRF9540. I don't know if this amp is like the 603 and 604 but if it is, the quality isn't that great (in my opinion). It's not going to fall apart but they run components (in the 603and 604) so hot that they'll damage the board. The damage is obvious on amps that have been used for an extended period of time. It may not be as severe on this amp due to the lower rail voltage. If you have time, try this. Let the amp idle for ~3-4 minutes and set the DC offset. Let it continue to idle and confirm that the DC offset has held. Switch the amp off and let it cool for 10-15 minutes. Power it back up and check the DC offset again. What's the DC offset ~15 seconds after powering it up from a cold start? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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27th March 2010, 04:28 PM	#3
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Once I get replacement parts I will give it a go. The power supply fets physically burnt up, no damage to the board at all. It had 60ne06-16 placed. I replaced those with RFP50n06, the supply seems to be ok. My observation was based on solder quality, no flux residue and sm components placed value up. If the design is marginal I could have a polished turd on my hands!

29th March 2010, 03:44 AM	#4
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	So I replaced all the outputs with a combination FQP33n10 and SFP9540. Idle current has been steady at 1 amp warm and cold. I measure this using a .005 ohm resistor inline with B+. Power numbers unloaded are 18.5Vrms front channels and 25.5Vrms rear/mono channel. I will throw my 3 ohm load on them and get a feel for real power output. cory

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