replaced irfz48n transistors.. still blowing fuses

DcMaN · 07:00 PM

Hey guys, i thought i would start by attempting to fix the jl 300/4 but that might be too advanced for me right now. I figured id start with something that is less complicated. I had a directed d800 that was popping the amp fuses, not the inline ones. So i took the amp apart and noticed there was a irfz48n that was shorted out (see pic) Anyway i replaced all 4 of them, and i powered the amp on it worked for a few minutes but i noticed the ground wire was getting really hot. So i took it off checked everything out, everything looked ok. But then when i hooked the amp back up it kept popping the inline fuses not the amps fuses. Any ideas ?

Thanks

-Rob

Perry Babin · 1st September 2010, 08:11 PM

Can you post a photo of the inside of the amp?

DcMaN · 1st September 2010, 09:34 PM

Ill post a picture as soon as i get home from work.

-Rob

DcMaN · 2nd September 2010, 02:33 AM

Perry Babin · 2nd September 2010, 02:46 AM

Remove the rectifiers. Does the amp blow the fuse (15 amp fuse suggested below).

Insert a 15 amp fuse in the B+ line and clamp all remaining components tightly to the heatsink before applying power.

DcMaN · 2nd September 2010, 02:56 AM

so remove those 4 that i just put in (the ones with out the heatsink on)?

Perry Babin · 2nd September 2010, 03:00 AM

The Z48s are the power supply FETs. The rectifiers are near the large capacitors (possibly fully encapsulated -- difficult to see in the photo).

The heatsink is the large aluminum outer shell. The missing parts in the photo are clamps.

DcMaN · 2nd September 2010, 03:07 AM

they are indeed fully encapsulated im removing them now ill let you know in a few min

DcMaN · 2nd September 2010, 04:01 AM

ok, so after removing the rectifiers, the inline fuse doesnt blow, but it puts my regulated powersupply into protect.

Perry Babin · 2nd September 2010, 04:20 AM

What's the current rating of the power supply?

1st September 2010, 06:35 PM	#1
DcMaN diyAudio Member Join Date: Aug 2010	replaced irfz48n transistors.. still blowing fuses Hey guys, i thought i would start by attempting to fix the jl 300/4 but that might be too advanced for me right now. I figured id start with something that is less complicated. I had a directed d800 that was popping the amp fuses, not the inline ones. So i took the amp apart and noticed there was a irfz48n that was shorted out (see pic) Anyway i replaced all 4 of them, and i powered the amp on it worked for a few minutes but i noticed the ground wire was getting really hot. So i took it off checked everything out, everything looked ok. But then when i hooked the amp back up it kept popping the inline fuses not the amps fuses. Any ideas ? Thanks -Rob Last edited by DcMaN; 1st September 2010 at 07:00 PM.

1st September 2010, 08:11 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Can you post a photo of the inside of the amp? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

2nd September 2010, 02:46 AM	#5
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Remove the rectifiers. Does the amp blow the fuse (15 amp fuse suggested below). Insert a 15 amp fuse in the B+ line and clamp all remaining components tightly to the heatsink before applying power. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

2nd September 2010, 03:00 AM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	The Z48s are the power supply FETs. The rectifiers are near the large capacitors (possibly fully encapsulated -- difficult to see in the photo). The heatsink is the large aluminum outer shell. The missing parts in the photo are clamps. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

2nd September 2010, 04:20 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What's the current rating of the power supply? __________________ 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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1st September 2010, 09:34 PM	#3
DcMaN diyAudio Member Join Date: Aug 2010	Ill post a picture as soon as i get home from work. -Rob

2nd September 2010, 02:33 AM	#4
DcMaN diyAudio Member Join Date: Aug 2010

2nd September 2010, 02:56 AM	#6
DcMaN diyAudio Member Join Date: Aug 2010	so remove those 4 that i just put in (the ones with out the heatsink on)?

2nd September 2010, 03:07 AM	#8
DcMaN diyAudio Member Join Date: Aug 2010	they are indeed fully encapsulated im removing them now ill let you know in a few min

2nd September 2010, 04:01 AM	#9
DcMaN diyAudio Member Join Date: Aug 2010	ok, so after removing the rectifiers, the inline fuse doesnt blow, but it puts my regulated powersupply into protect.

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