hep, Parasound pfet 900II - 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 12th December 2011, 02:05 AM   #1
yzriver is offline yzriver  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Boston, MA
Default hep, Parasound pfet 900II

Hi,

My parasound PFET 900II preamp doesn't work recently. One channel has a distorded sound, and there no output from the other channel except some humming.

Can anyone have ideal how to check it, or find a schematic?

Thanks,

Jay
  Reply With Quote
Old 16th December 2011, 02:53 AM   #2
yzriver is offline yzriver  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Boston, MA
I open the cover, and take some picture. I don't see any burned component. I can measure the regulator output +-25 and +-15.
Click the image to open in full size.

I check the relay first. It locates at bottom center of the picture, and it is model KUAN HSI D2A12, assumed it requirs 12V to turn on. However there is about 5.9V measured. Is it something wrong there? I post there picture here. Can anyone guess the circuit beside it?
Click the image to open in full size.

thanks,

Last edited by yzriver; 16th December 2011 at 03:01 AM.
  Reply With Quote
Old 16th December 2011, 03:46 AM   #3
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Should be +/- 15V. Regulator is gone?
  Reply With Quote
Old 17th December 2011, 02:51 AM   #4
yzriver is offline yzriver  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Boston, MA
Hi, John, Thanks for your reply.
The regulators are fine. I have +/-24V and +/-15V measured.
I found the problem is from the relay circuit. The relay is D2A12. I measure the voltage across the coil, one side is 11.93V, the other side is 5.55V, after I turn the machine on for a while. There is no change even I stay longer. Then I measure the resistance between the poles. One side is 0ohm, the other side is open. I believe there is something wrong in the relay circuit. So I short the poles by jumping wire for both side. Now music come out from both side.
I would like to solve this problem completely. The resistor have right value. The caps have no short. Is it possible those two transistors are gone?
Click the image to open in full size.

thanks,
  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
parasound HCA-1206 (Tony at Parasound.com) ostie01 Solid State 1 10th July 2012 06:24 AM


New To Site? Need Help?

All times are GMT. The time now is 04:57 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