Phase Linear 700 Series II - 60Hz Hum - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 19th September 2008, 01:38 AM   #1
diyAudio Member
 
Join Date: Jul 2004
Location: New York
Default Phase Linear 700 Series II - 60Hz Hum

I am running a pair of JBL 4343's, powered by a pair Phase Linear 700's bi-amped. One is a 700B (low amp), one is a fully complementary 700 Series II (mid's and hi's amp).

I like to cut the mid-hi amp gain (Series II) back about 3dB. The more I cut the gain, the more a 60Hz hum gets louder. It's loudest point is when the knobs are at about 12:00, then it decreases all the way down to full off.

Is my problem caps that need to be replaced? (electrolytics?? filter caps??)

Could the internal crossovers' caps be going due to age and heavy usage??

Or could it possibly be a ground problem with the active crossover that I'm using... Which by the way is based on the MOX design for the 4343's, with the help of Ian MacKenzie.

Any help is greatly appreciated.

Thanks,
Craig
  Reply With Quote
Old 21st September 2008, 10:36 AM   #2
d3imlay is offline d3imlay  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Ohio
If you disconnect the input jacks is there still any hum? The 700's are quiet with no input attached. The setting of the pots shouldn't make any difference. Whenever I work on any P/L amp I always change the RCA's out as they get loose and intermittent.

The PS caps should have less than a few hundred millivolts of ripple at idle. At full load it will be slightly over 1 volt.
  Reply With Quote
Old 24th September 2008, 01:31 PM   #3
diyAudio Member
 
Join Date: Jul 2004
Location: New York
I disconnected both RCA inputs. The hum is still present. Both amps are running through a Topaz Isolation Transformer too.

What does this mean?

Amp Caps?

Thanks,
Craig
  Reply With Quote
Old 25th September 2008, 09:56 AM   #4
d3imlay is offline d3imlay  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Ohio
Did you check the ripple? Why the xfmr?
  Reply With Quote
Old 25th September 2008, 10:34 AM   #5
diyAudio Member
 
Join Date: Nov 2002
Power supply caps are a problem with this amp especially considering its age. Replace them.
  Reply With Quote
Old 27th September 2008, 11:14 AM   #6
d3imlay is offline d3imlay  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Ohio
Quote:
Originally posted by burnedfingers
Power supply caps are a problem with this amp especially considering its age. Replace them.
Easier said than done. The originals are 9800uf @100V. They run right around 100V. With caps you buy today you don't get the headroom like you did 20 years ago. I'd want to go with 125V. Problem is that even at 100V they're hard to find and must be the same size or smaller.

If anyone can point me to some please do.
  Reply With Quote
Old 28th September 2008, 02:45 AM   #7
diyAudio Member
 
EchoWars's Avatar
 
Join Date: Dec 2002
Location: Left of the Dial
I'm not so sure that's true with some of the top-tier manufacturers, such as Vishay/Sprague (36DA & 36DX) and Nippon Chemi-Con (United Chemi-Con)(36DA). The latter of those two makes exceptionally well-built caps.
  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
Phase Linear 200 Series 2 IrishboyM4 Solid State 23 28th May 2008 03:04 AM
Phase Linear 400 Series 2 Repair rwagoner Solid State 50 1st September 2007 03:01 AM
Phase Linear 700B Series II -Right channel out- Kyllswytch Solid State 22 28th March 2007 01:53 AM
Clair Bros Phase Linear 700B Series 11 macka Swap Meet 3 24th January 2004 04:18 PM
Phase Linear 5100 Series Two Manual? Netlist Solid State 0 1st August 2003 09:36 AM


New To Site? Need Help?

All times are GMT. The time now is 03:38 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