Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Planars & Exotics ESL's, planars, and alternative technologies

Quad 2805 power supply malfunction?
Quad 2805 power supply malfunction?
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 January 2019, 10:15 AM   #21
clog is offline clog  Netherlands
diyAudio Member
 
Join Date: Jun 2012
Mats31, This is very useful information. Especially your remarks regarding the use of bees wax to cover the HV points. In the mean time I ordered panasonic smoothing caps and nichicon bipolars. Stokessd informed me that usually he bypassed the bipolar with a 8.2uf polyprop.
There is a contradiction with the (2805)2905 schematic. The 220u bipolar on the actual board is 50v rated whereas the offical schematic is indicating a 250v part.
To be honest Iím not impressed by what seems official technical documentation of these eslís as available on the net.
  Reply With Quote
Old 14th January 2019, 11:26 PM   #22
stokessd is offline stokessd  United States
diyAudio Member
 
stokessd's Avatar
 
Join Date: Nov 2002
Location: Grantham, NH
The documentation is effectively non-existent on the net, and the 2905 manual that is floating around has a couple of errors on the schematic as well. If the quality of the official documentation bothers you, you should check out the quality of the fasteners and hardware in the speaker itself.

I use 100v 220uF caps to replace the originals when necessary. I also just bypass that cap with a 8.2uF polyprop cap. it all fits without heroic measures.

If you have a 988 or newer, you can fit coke can polyprop caps under the plinth. These are what I've used in the past, although honestly, I don't think it's worth it vs. just using the 8.2uF bypass:

Solen 200uF 400V Polypropylene Capacitor


Sheldon
quadesl.com
  Reply With Quote
Old 16th January 2019, 03:20 PM   #23
AVWERK is offline AVWERK  United States
diyAudio Member
 
AVWERK's Avatar
 
Join Date: Jan 2004
Location: So Calif.
Good to know an expensive PP cap isnt necessary.

I purchased 5 Bennic 200 uf caps to get a matched pair and matched them with a 16 uf wondercap PP to arrive at the same value.
Also replaced the 1.5 ohm WW with a non inductive 12 wt

Regards
David
  Reply With Quote
Old 17th January 2019, 08:45 PM   #24
bolserst is offline bolserst  United States
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
Quote:
Originally Posted by stokessd View Post
…These are what I've used in the past, although honestly, I don't think it's worth it vs. just using the 8.2uF bypass.
What about the polyfuse used in the later Quads like the 2805? It is in series with the capacitor...likely there to help avoid amplifier damage when the SCR clamp activates, but the earlier iterations did not have it. I wonder about the sonic impacts. Have you experimented with bypassing it?
  Reply With Quote
Old 18th January 2019, 02:12 PM   #25
clog is offline clog  Netherlands
diyAudio Member
 
Join Date: Jun 2012
In post 13 member bolserst advised me to take measurements of DCV and ACV across the 1000uF cap in the power supply of my ESL. The results in post 15 seemed to indicate that this cap was bad.

Today I replaced the supposedly bad 1000uF capacitor in my 2805 by a fresh Panasonic FR series cap. Of course I was curious enough to take the same measurements again. I was measuring with two meters an analog and a digital one.

Analog VDC 15V
Analog VAC 30V (stable reading)
Digital VDC 15.5V
Digital VAC the same rythmic repeating pattern 38,15,6,2,0 V

And now I am completely flabbergasted. Does anyone has a clue ????

Right now I don't know if the distortion in the esl is still there. I couldn't audition it properly because the ESL is on my workbench. Tomorrow is the proof of the pudding.
  Reply With Quote
Old 19th January 2019, 12:31 PM   #26
stokessd is offline stokessd  United States
diyAudio Member
 
stokessd's Avatar
 
Join Date: Nov 2002
Location: Grantham, NH
Quote:
Originally Posted by clog View Post
In post 13 member bolserst advised me to take measurements of DCV and ACV across the 1000uF cap in the power supply of my ESL. The results in post 15 seemed to indicate that this cap was bad.

Today I replaced the supposedly bad 1000uF capacitor in my 2805 by a fresh Panasonic FR series cap. Of course I was curious enough to take the same measurements again. I was measuring with two meters an analog and a digital one.

Analog VDC 15V
Analog VAC 30V (stable reading)
Digital VDC 15.5V
Digital VAC the same rythmic repeating pattern 38,15,6,2,0 V

And now I am completely flabbergasted. Does anyone has a clue ????

Right now I don't know if the distortion in the esl is still there. I couldn't audition it properly because the ESL is on my workbench. Tomorrow is the proof of the pudding.

The AC voltage shouldn't be that high. It should be a few hundred mV. Does your meter auto-range and you are on the mV scale? Are you measuring right across the cap or from some other reference point?

Sheldon
  Reply With Quote
Old 19th January 2019, 12:36 PM   #27
stokessd is offline stokessd  United States
diyAudio Member
 
stokessd's Avatar
 
Join Date: Nov 2002
Location: Grantham, NH
Quote:
Originally Posted by bolserst View Post
What about the polyfuse used in the later Quads like the 2805? It is in series with the capacitor...likely there to help avoid amplifier damage when the SCR clamp activates, but the earlier iterations did not have it. I wonder about the sonic impacts. Have you experimented with bypassing it?
I haven't done a lot of tested of its effects, I consider it a safety device and wouldn't defeat it in speakers that I repair for others. For my use, I might bypass it though. When not triggered it has a quite low resistance and effectively not doing a whole lot in the circuit. There's a lot in the speaker that could mess with the sound as much or more than the polyfuse, like the diode bridge and zeners that you are playing in parallel with the panels. And the big series electrolytic cap that we mentioned earlier.

Sheldon
  Reply With Quote
Old 19th January 2019, 02:31 PM   #28
clog is offline clog  Netherlands
diyAudio Member
 
Join Date: Jun 2012
I am measuring at pins 1 and 4 of the 555 ic
  Reply With Quote
Old 19th January 2019, 04:58 PM   #29
bolserst is offline bolserst  United States
diyAudio Member
 
bolserst's Avatar
 
Join Date: Jun 2005
Location: Fort Worth, Texas
what make/model of voltmeter are you using? stokessd has a good point...if it is auto-ranging, you might be seeing 38mVAC instead of 38VAC which means the power supply is fine. Some meters have buttons to over-ride the auto-ranging and manually cycle thru ranges. If you are indeed seeing 38VAC and 15VDC with the new capacitor, as unlikely as it sounds, the bridge rectifier D14 may be faulty.

Last edited by bolserst; 19th January 2019 at 05:04 PM.
  Reply With Quote
Old 19th January 2019, 06:28 PM   #30
martin clark is offline martin clark  Europe
diyAudio Member
 
Join Date: Jul 2003
Location: Bath, UK
re: odd VAC meter readings - it could also be that like many cheap DVMs, clog's does not read AC volts cleanly in the presence of DC offset.
- ie VAC riding on top of the 16v or so DC on this supply.


Try coupling one lead to the meter through a 0.1 - 1uF capacitor when trying to read Vac and see what the meter shows once it settles in 5-10seconds (NB no need for large capacitor value: the meter input impedance will be tens of megaohms, or more; so there will be a slow settling time while the cap charges to the full DC if you use a larger-value cap)
  Reply With Quote

Reply


Quad 2805 power supply malfunction?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Quad ESL57 EHT power supply PCB freebee Planars & Exotics 2 29th August 2017 06:42 AM
New power supply for Quad 405 cowana Power Supplies 0 11th July 2012 01:12 PM
Quad 405 Op-Amp Power Supply Thomo Solid State 6 19th July 2007 12:49 AM
Quad ESL 2805 lilu Pass Labs 4 22nd March 2007 06:26 PM
Upgrading Power Supply in QUAD 606 Mk2 arupg Solid State 0 17th March 2007 05:56 AM


New To Site? Need Help?

All times are GMT. The time now is 03:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki