oneplustwo Aleph X build thread - Page 8 - 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 26th December 2012, 08:47 PM   #71
diyAudio Member
 
dimkasta's Avatar
 
Join Date: May 2010
Location: Athens
Holly crap.... that thing looks amazingly huge
Can you throw something in there for size reference? Like a CD or something?
  Reply With Quote
Old 26th December 2012, 09:19 PM   #72
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
Yes, it is. See post #41 for reference: oneplustwo Aleph X build thread
__________________
My Projects
  Reply With Quote
Old 29th December 2012, 06:25 AM   #73
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
A few more pics in progress.

MOSFETs mounted on the heat sink and daughter board:
Click the image to open in full size.

Soldering the wires was a pain. The holes in the board are way too big for the 14GA wire I'm using.

Similar issue with the main board:
Click the image to open in full size.

Rough layout of where things will go. I ended up mounting the PSU board on the heat sink itself to get it out of the way.
Click the image to open in full size.

QUESTION: My transformers have 4 secondaries where I only need 2. I believe I'm supposed to just wire 2 pairs in parallel to the PSU board, correct? The wires are also super beefy, at least 12GA... I'm going to have to solder the pairs together and down gauge to get them to fit in the board.
__________________
My Projects
  Reply With Quote
Old 29th December 2012, 06:54 PM   #74
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
I assume from your post that the secondaries are all the same voltage and that two secondaries will supply sufficient current for the amplifier.

Even if that's the case I would use the other two secondaries as well. The only reasonable way to do this is to use a separate rectifier bridge (or bridges) for the two extra windings and parallel these with the outputs of the existing bridge or bridges.

Don't parallel the secondaries directly.

Graeme
  Reply With Quote
Old 29th December 2012, 07:59 PM   #75
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
Hmm, I had not considered not being able to parallel the secondaries. If that's the case, then did my 800VA transformers just become 400VA? If I do parallel, do bad things happen or is it just not "kosher?" I suppose worst case scenario I can do exactly as you say and add another set of rectifiers. Just makes it more complicated than I was hoping for.
__________________
My Projects
  Reply With Quote
Old 29th December 2012, 09:41 PM   #76
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Your transformers are Antek AN-8420, yes?

I think you can just parallel 2 pair of the secondaries to make 20v+20v at 800VA
  Reply With Quote
Old 29th December 2012, 11:17 PM   #77
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
Yes, I have two of the 8420's. After doing a little google searching, my understanding is that the VA ratings are based on making sure you don't have so much power as to saturate the core and also making sure the wires are heavy enough to handle the current. I suppose resulting temperature rise is another factor to consider.

So I think I'll just go ahead and use two of the secondary pairs and leave the other two alone. Just cover up the ends with some shrink and tuck them away somewhere.
__________________
My Projects
  Reply With Quote
Old 3rd January 2013, 10:04 PM   #78
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
Ok... I'm almost to the point of first power on. So far, I've just checked both of the PSU. They output +/- 27VDC without any load as expected. (They are CRC with CL-60 thermistors on each primary winding and 5 1R resistors paralleled for the 'R'.)

I've double checked the wiring and triple checked the polarity of the PSU connections. Now, just need to check once more. Or maybe sleep on it and then check again. Then... I'll use my new Variac to dial up some juice. I figure I'll get to +/- 10V PSU rails and make sure nothing smokes.

QUESTION: Any reco on input caps? I had forgotten to get these so I'm looking for a range of what's acceptable so I can raid my parts bin for something that can get me by for the short term at least.

EDIT: Looks like I have exactly (4) 4.7uF Dayton Audio caps left over from an old crossover. We're in business...
__________________
My Projects

Last edited by oneplustwo; 3rd January 2013 at 10:33 PM.
  Reply With Quote
Old 4th January 2013, 06:13 AM   #79
diyAudio Member
 
oneplustwo's Avatar
 
Join Date: Apr 2009
Location: San Francisco
I couldn't wait... took the plunge and powered up! Both amps were turned up to 10VDC first with the Variac to see how things were shaking out. No smoke. No smells. No sounds. Whew! Checked source resistors and got a very consistent 0.5V throughout.

Time to go to 110VAC!!!

Checked the following:
- Rechecked source resistors and got the same result, dropped off slightly as things warmed up. Whew!
- Absolute DC offset was about 10.7V. In the normal range. Whew!
- Relative DC offset was zero but no inputs connected so I didn't expect anything here. Whew!

At this point, I powered down as I didn't want to push my luck. Also, I wanted to try the other channel to replicate what I had just done. Basically the same result.

However... on the first one, I noticed the rectifier heat sinks (MUR1520) were getting really really hot. And on the second one, I noticed a tiny bit of smoke from them. Not sure if that's just my greasy finger residue burning off or not. In any case, I'm wondering if I need to rethink the rectifiers. I thought the 15A rating for these would be good enough. And maybe I just need to go back and apply thermal grease to them. The heat sinks they're mounted to aren't much but perhaps the thermal grease will make a big enough difference to cool them down.

Would welcome any thoughts!
__________________
My Projects
  Reply With Quote
Old 4th January 2013, 07:46 AM   #80
diyAudio Member
 
Join Date: Feb 2009
rethink your rectifiers get som 30A or higher and mount tham on the big bottom plate, if it's alu.
  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
Loudspeaker Build Thread Hsmeets Multi-Way 67 15th August 2012 01:30 PM
oneplustwo F5 build thread oneplustwo Pass Labs 251 30th May 2012 09:36 PM
oneplustwo DCB1 Black, White and Red build thread oneplustwo Pass Labs 1 26th February 2012 06:11 AM
aikido build thread- nate Tubes / Valves 1 27th February 2009 05:01 AM
Dan's Aleph Build Thread monarodan Pass Labs 19 14th February 2007 11:06 AM


New To Site? Need Help?

All times are GMT. The time now is 03:50 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