Aleph5 (MiniA) in flames - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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
Reply
 
Thread Tools Search this Thread
Old 22nd April 2008, 11:07 PM   #1
stighe is offline stighe  Norway
diyAudio Member
 
Join Date: Nov 2007
Default Aleph5 (MiniA) in flames

Hi

I'm building an Aleph5 (miniA-PCBs). I connected one channel only to test and actually everything worked fine for about 3 minutes.

Then something strange happened!

Music stopped and two resistors caught fire. First R29 on one of the output boards, then R21 on the Amplifier board.

I have checked every wire, but everything seems fine. There's no visible damage to the other components on the cards.

Please see http://www.diyamps.com/aleph for PCB layouts and schematics.

Thank you
  Reply With Quote
Old 23rd April 2008, 03:36 AM   #2
gni is offline gni  United States
diyAudio Member
 
gni's Avatar
 
Join Date: Sep 2006
Had problem using the supplied link to the schematic.

Sounds almost like thermal runaway. . .Class A
except the mosfet has a reverse thermal coefficient.


A bad solder joint.

There will be better answers. . .
  Reply With Quote
Old 23rd April 2008, 04:35 AM   #3
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
The occasional flame is part of the game,

but the Alephs are not known for runaway bias, the DC value
being locked by a PN junction voltage.
  Reply With Quote
Old 23rd April 2008, 10:48 AM   #4
diyAudio Member
 
Tarasque's Avatar
 
Join Date: Dec 2002
Location: Netherlands
I would check the insulation from the output devices to the heatsink. I've had similar problem what metal dust from drilling mounting holes was piercing the insulator pads, connecting the upper and the lower fet banks.

I have to say...A spectacular event when these power fets explode...
  Reply With Quote
Old 24th April 2008, 08:07 PM   #5
folkeb is offline folkeb  Norway
diyAudio Member
 
Join Date: Jan 2006
Location: Trondheim
What would you suggest be the best way of figuring out this rather explosive incident. We really thought that everything was working rather well, and then suddenly a thump in the speaker and then flames. First from the negative board on the heatsink, a 221 ohm resistor, then another 221ohm resistor on the main board.

Would you try hooking up the other channel (only using the PS)?

This incident sort of drained any motivation..but weŽll get over it!

Thanks for any help!

- Folke
  Reply With Quote
Old 25th April 2008, 01:29 AM   #6
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
Would anyone have links that work to the brianGT schematic and part list for the mini A?



I have the threads bookmarked but I haven't been able to access the diyamps or chipamps site.

Fran
  Reply With Quote
Old 25th April 2008, 01:41 AM   #7
diyAudio Member
 
mpmarino's Avatar
 
Join Date: Jun 2004
Location: Crunchville, where I don't fit in.
Quote:
a 221 ohm resistor
without the schem it's tough to tell exactly what part toasted, but your indicating a 221r resistor indicates that a gate resistor maybe blew. I'd check the output device corresponding to that resistor for a short....
__________________
Crazy Yankee.
  Reply With Quote
Old 25th April 2008, 08:53 AM   #8
diyAudio Member
 
Tarasque's Avatar
 
Join Date: Dec 2002
Location: Netherlands
Hi Folke,

When the insulation is OK, I would check the thermal coupling to the heatsink. This phenomena can also happen when the junction reaches >150C temp.

A burnt gate resistor is one of the typical events when the fet has a thermal overload.

Before firing the 2nd channel, I would check all components on the PCB as well as the insulation and the thermal coupling of the output devices.
  Reply With Quote
Old 25th April 2008, 10:02 AM   #9
folkeb is offline folkeb  Norway
diyAudio Member
 
Join Date: Jan 2006
Location: Trondheim
As a matter of fact the heatsinks were rather warm after only a few minutes. Didn't check the temperature of the fets as we were busy putting out the fire...
  Reply With Quote
Old 26th April 2008, 12:00 AM   #10
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
I almost have my casework finished and will be doing some wiring soon! I hope i don't see smoke!!!

Was there ever a set of instructions/schematic etc for the brianGT boards?

Fran
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
1 channel of MiniA working - measurments Stabist Pass Labs 55 8th November 2005 08:51 AM
MiniA strange behaveur Stabist Pass Labs 3 27th October 2005 10:44 PM
MiniA & BoZ integrated amp Stabist Pass Labs 8 12th March 2004 12:38 AM


New To Site? Need Help?

All times are GMT. The time now is 11:14 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2