Aleph 2 fuse burned and killed mosfet!

Aerosol · 16th November 2002, 07:13 AM

Hi there,

Please pardon me for this triteness but I really need your help!!

I am building another set of Aleph 2 using BrianGT's layout and found that the fuse burned 5 seconds after I powered on the amp.

I've checked my PSU without main board connected and got (+50V)-0-(-50V) with happy fuse. Can I conclude that my PSU is good?? The PSU was using the Aleph 4 design.

When it blew out the fuse, I found both bias and output group have one MOSFET destroyed by the current. It seems that it just picked one MOSFET randomly from each group everytime when I replaced the bad one.

No burned sign shown in the main board.

Any suggestion I can do to kick the bad guy out of my circuit??
Thanks!!

swede · 16th November 2002, 09:30 AM

Hi,

You are lucky you didn't blow more than one. Well, one reason for not blowing more of them is that a "blown" FET usually transforms to a short circuit, letting all the current flow through it (the broken one).

To mee it sounds like you either have FET's with too low voltage specs, or WAY TOO MUCH bias. (short circuit somewhere close to R18?, R19?; cold solder at R19?; solder smeared on the board, shorting something?)

Do you have any pictures on your board?

//magnus

wuffwaff · 16th November 2002, 12:15 PM

Aerosol,

does it blow at once or does it take a few minutes?
I once had a bad heat transfer from one fet to heatsink (screw too long

) so it got too hot and died.

william

Aerosol · 16th November 2002, 07:50 PM

The fuse burned in 5-10 seconds and the mosfet already dead at that time.

I will re-check every solder point later today to make sure I have no cold solder on my baord. I used 3% silver solder and set my solder temp to 300C (~570F) which might be a potential problem becuase this this my first to use high silver content solder.

I will also get a picture and post it later.

Thanks guys for your time and help!!!

-Victor

16th November 2002, 07:13 AM	#1
Aerosol diyAudio Member Join Date: Dec 2001	Aleph 2 fuse burned and killed mosfet! Hi there, Please pardon me for this triteness but I really need your help!! I am building another set of Aleph 2 using BrianGT's layout and found that the fuse burned 5 seconds after I powered on the amp. I've checked my PSU without main board connected and got (+50V)-0-(-50V) with happy fuse. Can I conclude that my PSU is good?? The PSU was using the Aleph 4 design. When it blew out the fuse, I found both bias and output group have one MOSFET destroyed by the current. It seems that it just picked one MOSFET randomly from each group everytime when I replaced the bad one. No burned sign shown in the main board. Any suggestion I can do to kick the bad guy out of my circuit?? Thanks!!

16th November 2002, 12:15 PM	#3
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	Aerosol, does it blow at once or does it take a few minutes? I once had a bad heat transfer from one fet to heatsink (screw too long ) so it got too hot and died. william __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
HELP Aleph 5 is burned?	zigo3	Pass Labs	5	20th February 2008 12:00 PM
Aleph 0s fuse value	Sony	Pass Labs	3	3rd October 2005 05:36 AM
burned JLH fuse by connecting to Tube preamp	rchung	Solid State	3	28th September 2004 09:51 PM
Kicker ZR1000 mosfet burned...	xbcaraudio	Solid State	2	10th March 2004 08:44 PM
I burned my Aleph 3! Please help!	Jesse	Pass Labs	25	26th October 2003 01:56 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

16th November 2002, 09:30 AM	#2
swede diyAudio Member Join Date: Sep 2001 Location: Geneva, Switzerland	Hi, You are lucky you didn't blow more than one. Well, one reason for not blowing more of them is that a "blown" FET usually transforms to a short circuit, letting all the current flow through it (the broken one). To mee it sounds like you either have FET's with too low voltage specs, or WAY TOO MUCH bias. (short circuit somewhere close to R18?, R19?; cold solder at R19?; solder smeared on the board, shorting something?) Do you have any pictures on your board? //magnus

16th November 2002, 07:50 PM	#4
Aerosol diyAudio Member Join Date: Dec 2001	The fuse burned in 5-10 seconds and the mosfet already dead at that time. I will re-check every solder point later today to make sure I have no cold solder on my baord. I used 3% silver solder and set my solder temp to 300C (~570F) which might be a potential problem becuase this this my first to use high silver content solder. I will also get a picture and post it later. Thanks guys for your time and help!!! -Victor