Kenwood KAC-628

mike49504 · 10th May 2010, 11:18 AM

I recieved this amp in for repair. The power suply fets are IRFZ34G's Wondering if i can swap them out for IRF1010N's?

Perry Babin · 10th May 2010, 02:10 PM

It looks like they will work (assuming that the drive circuit is the same as the 728) but you'll need to confirm that they don't run hot at idle. If they do, you'll have to replace the 68 ohm gate resistors with 47 ohm resistors.

mike49504 · 11th May 2010, 12:08 PM

Perry,

I stuck the IRF1010N's in this amp and it draws excessive current and the 1010n's get red hot. I checked the drivers they seem to check fine But i cant seem to find the gate resistors for this amp.

mike49504 · 11th May 2010, 02:32 PM

Only resistors i see connected to the first leg of the fets are 1.5K ohm (brown,green,red,gold)

brandes.cm · 03:59 PM

Don't know how close the KAC-606 or 626 are to one you are working on, but the manual can be found here.
(bottom of page)
R104-108 look to be 100ohm.
https://sites.google.com/site/brandescm/home/projects

Zooming in on your pic shows the board #'s to match the service manual in my link.

mike49504 · 11th May 2010, 06:35 PM

Ok only resistors i saw connected to the fets are

LEG1:1.5K ohm

Leg3:10 ohm

With the IRF1010N's in the amp they heat up within a sec and blows the fuse to the amp.

The drivers test fine So wondering what do i check or need to do at this point

brandes.cm · 11th May 2010, 07:01 PM

I was looking at the outputs when I quoted R104-108. The power supply fets look to be driven directly from the 494/594 through R123 and R124. Those tie to 1.5K R126 and R125. R125 and 126 are acting as pull down resistors, keeping the gate low when not on. Are the 10ohm parts OK. Is the xfrmer shorted or anything in the secondary side to the supply?

Perry Babin · 12th May 2010, 12:27 AM

If the only component that's pulling the gate voltage down is the 1.5k ohm resistor, you will need to reduce their value to use the 1010s. A 330 ohm should be sufficient. If it's not, you may have to use a different FET (one that's easier to drive).

mike49504 · 12th May 2010, 03:28 PM

Wondering would the 2sc4064's work for the fets?

Perry Babin · 12th May 2010, 03:36 PM

That's not a good sub. Did you try try reducing the value of the gate pulldown resistor?

If all else fails, you could order the original parts.

10th May 2010, 11:18 AM	#1
mike49504 diyAudio Member Join Date: Sep 2006	Kenwood KAC-628 I recieved this amp in for repair. The power suply fets are IRFZ34G's Wondering if i can swap them out for IRF1010N's?

10th May 2010, 02:10 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	It looks like they will work (assuming that the drive circuit is the same as the 728) but you'll need to confirm that they don't run hot at idle. If they do, you'll have to replace the 68 ohm gate resistors with 47 ohm resistors. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

11th May 2010, 03:54 PM	#5
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Don't know how close the KAC-606 or 626 are to one you are working on, but the manual can be found here. (bottom of page) R104-108 look to be 100ohm. https://sites.google.com/site/brandescm/home/projects Zooming in on your pic shows the board #'s to match the service manual in my link. Last edited by brandes.cm; 11th May 2010 at 03:59 PM.

12th May 2010, 12:27 AM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If the only component that's pulling the gate voltage down is the 1.5k ohm resistor, you will need to reduce their value to use the 1010s. A 330 ohm should be sufficient. If it's not, you may have to use a different FET (one that's easier to drive). __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

12th May 2010, 03:36 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	That's not a good sub. Did you try try reducing the value of the gate pulldown resistor? If all else fails, you could order the original parts. __________________ 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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11th May 2010, 02:32 PM	#4
mike49504 diyAudio Member Join Date: Sep 2006	Only resistors i see connected to the first leg of the fets are 1.5K ohm (brown,green,red,gold)

11th May 2010, 06:35 PM	#6
mike49504 diyAudio Member Join Date: Sep 2006	Ok only resistors i saw connected to the fets are LEG1:1.5K ohm Leg3:10 ohm With the IRF1010N's in the amp they heat up within a sec and blows the fuse to the amp. The drivers test fine So wondering what do i check or need to do at this point

11th May 2010, 07:01 PM	#7
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	I was looking at the outputs when I quoted R104-108. The power supply fets look to be driven directly from the 494/594 through R123 and R124. Those tie to 1.5K R126 and R125. R125 and 126 are acting as pull down resistors, keeping the gate low when not on. Are the 10ohm parts OK. Is the xfrmer shorted or anything in the secondary side to the supply?

12th May 2010, 03:28 PM	#9
mike49504 diyAudio Member Join Date: Sep 2006	Wondering would the 2sc4064's work for the fets?

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