Aleph1.2 clone trouble - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 8th September 2008, 05:38 PM   #1
oblerum is offline oblerum  Norway
diyAudio Member
Join Date: Jan 2005
Location: Raufoss
Default Aleph1.2 clone trouble

I just finished aleph1.2 clones and am getting nearly no sound at all from it. I measure the same values when I measure left and right channel, see schematics.

Everything is as the schematics say except the MPSA 18 are replaced with BC 550 (yes I do know about the reversed pins, so they are turned 180 degrees)

Her are some facts/measures:

- amp built as per schematics (KK-PCB)
- hear very low signal trough amps
- The mosfets are matched within 0,015V, but will not heat up
- I measure 69 Volts over mosfets (no voltage drop at all), but no volts over R40-51
- Powersupply with testload measured 58V
- BC 550 used (not MPSA 18), otherwise original parts
- Q1, Q2 and Q3 are hot (but not to hot)

any help would be MUCH appreciated,
Ole Bjørn
Attached Images
File Type: jpg left_channelsmall.jpg (54.3 KB, 378 views)
Ole-Bjørn Lerum
  Reply With Quote
Old 8th September 2008, 05:50 PM   #2
Zen Mod is online now Zen Mod  Serbia
diyAudio Member
Zen Mod's Avatar
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
for start - instead R11 put 100R resistor in series with 100R pot ,then try to set pot to have nearer to 4V across R14 , chasing 0,5V across source resistors of output mosfets

to my eyes - you don't have enough current through input LTP (Q1,Q2) , so not enough current through R14 , so not enough voltage across it to open enough lower bank of output mosfets ;

one thing you didn't measured - output DC voltage ; I can bet that you have there near +55V
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
  Reply With Quote
Old 8th September 2008, 10:16 PM   #3
oblerum is offline oblerum  Norway
diyAudio Member
Join Date: Jan 2005
Location: Raufoss
Thank you!

I shall try this over the weekend, and post the answer when I tried it.

Ole-Bjørn Lerum
  Reply With Quote
Old 8th September 2008, 10:20 PM   #4
Manu is offline Manu  Europe
diyAudio Member
Manu's Avatar
Join Date: Nov 2002
Location: Vienna, Ostrich
Originally posted by Zen Mod

I can bet that you have there near +55V
Thats normal you're pita, sorry pithia of BaC afterall...

Naaah, just sincerely admirative how you can do ferndiagnose ...
You know what I mean...

I am always fascinated how some issues (when then solved) can bring so much understanding in a given matter...

  Reply With Quote
Old 9th September 2008, 02:55 AM   #5
john65b is offline john65b  United States
diyAudio Member
john65b's Avatar
Join Date: Jan 2005
Location: Chicago
I had a similar issue on a Zen v5 - one of may rails was not "on"
I Speak Spanish to God, Italian to Women, French to Men, and German to My Horse. Charles V
  Reply With Quote


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
Aleph1.7 nickgreek Pass Labs 35 14th May 2013 07:23 PM
aleph1.2 IRF240 vs IRFP250 klimo_67 Pass Labs 20 8th April 2010 02:17 PM
aleph1.2 klimo_67 Pass Labs 2 22nd March 2007 09:58 AM
Record-out buffer for Aleph1.7 joho Pass Labs 25 9th December 2004 08:34 PM
transformer of aleph1.2 john-china Pass Labs 1 22nd November 2001 05:08 AM

New To Site? Need Help?

All times are GMT. The time now is 11:03 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2