second aleph3 not working! - 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 18th August 2004, 08:45 PM   #1
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
Default second aleph3 not working!

so, after a LOT of headache from the first aleph3, i got the second chassis built, and its not working!

its the same design (an exact replica) of the one seen at my site

http://www.cowanrg.mesanetworks.net/projects/

and in this thread:

aleph3 built, but humming...

ive done some minor testing as of now. i was blowing fuses, and im still not sure why. i took the power supply apart, then put it back together, and that's fixed.

i accidentally had Q106 and Q107 wired backwards, that is now fixed.

right now, the power supply is good. im getting a nice +-26.66V from the caps. however, im getting almost no draw from the amp. i think i measured the + rail at 0.025A at idle. way too low. my other amp draws 1.88A (its an RMS meter, so that is right on).

the LED doesn't even come on, the fets dont get hot. i have yet to make any board measurements, but with the draw so low, i dont know if it would tell me anything... the only thing i can really tell about the board is that Q103 is getting hot. i left it on for a little bit, and it was quite warm, and everything else was cold.

any simple ideas? if not, ill just have to take it all apart
  Reply With Quote
Old 18th August 2004, 08:55 PM   #2
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
What's the voltage across R108, R106 and CE Q105?

/Hugo
  Reply With Quote
Old 18th August 2004, 08:59 PM   #3
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
i should add that the LED isnt coming on either. i didnt think that was important, but looking at the schematic, it appears like it could.
  Reply With Quote
Old 18th August 2004, 09:06 PM   #4
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Default Re: second aleph3 not working!

Quote:
Originally posted by cowanrg
the LED doesn't even come on(
Quote:
Originally posted by cowanrg
i should add that the LED isnt coming on either.
You did..

Time to get some sleep?

/Hugo
  Reply With Quote
Old 18th August 2004, 09:08 PM   #5
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
hah, duh.

its my day off. my brain doesnt like to work on my day off.
  Reply With Quote
Old 18th August 2004, 09:31 PM   #6
eLarson is offline eLarson  United States
diyAudio Member
 
eLarson's Avatar
 
Join Date: Aug 2002
Location: Gaithersburg, MD
Are there any pins shorted together (Gate to Source, say) such that MOSFETs won't be able to turn on?
__________________
Would a woodchuck bother to chuck MDF?
  Reply With Quote
Old 18th August 2004, 09:33 PM   #7
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
pins shorted on the actual fets you mean? i can check.
  Reply With Quote
Old 19th August 2004, 12:56 AM   #8
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
wow, i got some really neat readings...

first off, i followed Mike's advice and tested this amp against the working one.

to answer eLarson first, i am not getting any shorts on the fets. they seem ok i guess.

MikeW told me to measure voltage across Q101, Q102, and Q103. here is what i got on my first amp: 3.6, 3.5, and 3.5. a little low, but fine i guess. on the bad amp i get: 3.3, 52, 26.

(on the second transistor, reading on G was ~26v, and on S was -26v, so summed at 52v. on the third, it was 0v on G, and -26v on S).

so, there is definately something wrong there. do i replace Q102 and Q103? or is something else causing the error?
  Reply With Quote
Old 19th August 2004, 01:15 AM   #9
cowanrg is offline cowanrg  United States
diyAudio Member
 
cowanrg's Avatar
 
Join Date: Apr 2002
Location: Lafayette, CO
Send a message via AIM to cowanrg
wow.

i measured some resistors. across R108, R106, and Q105. all measurements were nothing! i got a 0v drop across them.

SO, power just isnt getting in. however, im measuring a 0.024A draw across the negative rail. so, power IS connected right, the caps are charging, so i would assume the power supply is ok. (i made measurements at each bridge, and each rail, all are fine).

oh, and i get ~26v or so at the component, so power is running through the board.
  Reply With Quote
Old 19th August 2004, 01:16 AM   #10
moe29 is offline moe29  United States
diyAudio Member
 
moe29's Avatar
 
Join Date: Dec 2002
Location: Florida
Send a message via AIM to moe29 Send a message via Yahoo to moe29
Looks like you are getting rail voltage on your FETS.

Your 3watt resistors probably got burned. Thus probably taking
out their corisponding FETS.

Yank 1 of the fets and test it to see if it's still good.

If it's bad you gotta find out why that happened.

Maybe a bad solder.

Replace the FETS and R's and try again.


just my quick thoughts.
  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
aleph3, 30 and 5 kslim Pass Labs 1 9th September 2004 02:58 AM
Aleph3 bridged? PatPet Pass Labs 6 13th April 2004 02:36 PM
my little Aleph3 moamps Pass Labs 16 27th August 2003 10:48 PM
Aleph3 HarryHaller Pass Labs 13 7th February 2002 03:46 AM
Aleph3 PSU victor Pass Labs 3 20th August 2001 12:42 PM


New To Site? Need Help?

All times are GMT. The time now is 08:36 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