Aleph 5 DIY- with Dolphin sounds...Help please - Page 5 - 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 13th June 2013, 01:20 PM   #41
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Sounds like you are anticipating problems...

Lets hope you crack it with this rebuild.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced. Click here to take the low impedance challenge
  Reply With Quote
Old 13th June 2013, 01:43 PM   #42
diyAudio Member
 
Join Date: May 2002
Location: oz
update

it wasn't the daughter board......progress!
__________________
george a
  Reply With Quote
Old 13th June 2013, 09:19 PM   #43
diyAudio Member
 
Join Date: Oct 2009
this might have been covered, but make sure there are no burrs around the mounting hole of the mosfet in question and the surface is smooth. burr will or could punch throught the insulator and short the drain to the heatsink.
  Reply With Quote
Old 14th June 2013, 05:38 AM   #44
diyAudio Member
 
Join Date: May 2002
Location: oz
thanks teeker
i will check
good call!
__________________
george a
  Reply With Quote
Old 23rd June 2013, 03:38 PM   #45
diyAudio Member
 
Join Date: May 2002
Location: oz
Hi All

Back again

after various pressures and priorities I found myself doing a complete (newish) build as I had a couple of spare A5 pcbs floating around....
It worked first time with all voltages ok...so that is very reassuring and pleasing .
So the A5 is installed back in the system and singing as sweetly as ever.
though not very hot as its fan cooled with large heatsinks (only abt 15deC rise over ambient..)

I really don't know what the problem was but interestingly a few odd parts appear to have fried themselves without me noticing - particularly the Source (1 ohm ) resistors.....

Anyway - I now have a few mosfets to check for damage (some shorted and some reading a very low Vgs..)

I still don't know what the problem was - and will as time allows do a rebuild on my 2 spare pcb's with the intention of placing them in my triamp system to cover 80hz-650hz, the repaired Aleph is covering from 650hz up...

One issue that has arisen is that when I fired up the amp I connected a "sacrificial" speaker just in case something was untoward- no probs except for buzz which is not really noticable on the main speaker (ribbon).
Now that I have an oscilloscope i had a look at the output with inputs shorted and noticed an odd looking waveform. ($40 for a 2nd hand CRO- money well spent!)

The strange waveform was also present on the power supply + & - with no load attached (no amplifier load as it a 2 box unit and I disconnected the power feed to the pcbs')

It could be some dodgy caps (4 x80kuF) or the diode bridges (2 squre box style wired in paralle.

I'll post an image of the waveform to see if anybody cleverer than I knows what it means ..


Most importantly - a big thanks to all have helped in getting the amp working again.
Your guidance , suggestions and observations are all very much appreciated.

I hope i can return the favor to the forum every now and then.

cheers from down under
__________________
george a
  Reply With Quote
Old 23rd June 2013, 04:17 PM   #46
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Thanks for the update George. Pleased to hear you have a working Aleph once again.

Yep, you can post the 'scope waveform and we'll hazard a guess
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced. Click here to take the low impedance challenge
  Reply With Quote
Old 24th June 2013, 11:40 AM   #47
diyAudio Member
 
Join Date: May 2002
Location: oz
well here tis
photo of scope view- as best as i can do

frequency of pulse i think equates to 100hz with abt 0.03v peak to peak voltage. (yes i calibrated the scope)

this is taken at the terminal of one of the power supply caps with no load on the power supply other than some bleeder resistors- abt 160ohms.
amp is totally disconnected.
power supply consists of:
a) 1 trafo - supposedly 50v ct with 50A secondary
b) 2 diode bridge blocks in parallel
c) 4 of 80kuF caps (total for + &-ve)
d) 160ohm bleeders per rail.
e) 1 small cap across one of the diode bridges
when i connect the amp i can hear a bit of a buzz through a highish efficieny speaker, but is pretty inaudible with the ribbons the amp usually drives.
amp is connected to the ribbon via a matching transformer.

Is the waveform telling us anything?

thanks in advance
Attached Images
File Type: jpg 100hz pulse.jpg (81.4 KB, 50 views)
__________________
george a
  Reply With Quote
Old 24th June 2013, 11:56 AM   #48
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
160R bleeders are loading it too much

say that 1K is mucho better

besides that , everything seems normal
__________________
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 24th June 2013, 12:06 PM   #49
diyAudio Member
 
Join Date: May 2002
Location: oz
Thanks Zen mod

I'll change over the little bleeders and report back
many thanks.

BTW the amp sounds wonderful- my kids use it a lot - they don't know just how good they've got it...thanks again papa
__________________
george a
  Reply With Quote
Old 24th June 2013, 12:11 PM   #50
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Sawtooth ripple like is what you would expect to see. That all looks perfectly normal.

If you can hear this ripple (and it will be far higher than 0.03 v pk/pk with the amp drawing current) then the two main possibilities are a less than perfect wiring scheme whereby some of that voltage is developed across and conductor and finds its way into the amp, and/or the ripple rejection of the amp itself allows some ripple present on the rails to pass to the output.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced. Click here to take the low impedance challenge
  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
Bring a dolphin to your next listening session sonidos The Lounge 5 18th July 2012 01:45 PM
Dolphin Hollow State Labs On-line Miles Prower Vendor's Bazaar 0 7th December 2009 07:01 PM
My Aleph p1.7 sounds wonderful ! zei Pass Labs 39 7th January 2007 10:25 PM
Which Aleph sounds best? Odysei Pass Labs 6 20th June 2004 04:34 PM
My Aleph sounds better! Gabster Pass Labs 32 23rd April 2002 12:43 AM


New To Site? Need Help?

All times are GMT. The time now is 06:16 AM.


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