Parasound HCA-3500 Bias issue - Page 2 - 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 9th February 2012, 03:37 PM   #11
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
NO, I do NOT do repairs. Please live with it, or send it to Parasound.
  Reply With Quote
Old 10th February 2012, 02:17 AM   #12
diyAudio Member
 
Join Date: Jun 2010
no i mean. can anyone get me a repair manual so that I could service it myself?
  Reply With Quote
Old 10th February 2012, 04:19 AM   #13
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Can you, jck, do it without screwing it up? If you can do it, and TRUST your capabilities, then get two medium size clip leads. Attach one end of each to a multimeter that can measure milliVolts. When you open the case, find ONE convenient EMITTER RESISTOR to put the opposite clip lead ends, across the resistor. Now you are in a position to measure .015-.025 Volts.
Attach clip leads BEFORE turning on the amp. Wait at least 1/2 hour before determining the final quiescent current as determined by the voltage drop across the EMITTER RESISTOR.
IF the voltage drop, over time is NOT in the range of .015-.025 Volts, then find the trim pot that adjusts the measurement. You have to look for it. BE VERY CAREFUL NOT TO TURN THE POT TOO MUCH, until you get a feel for its range.
That should do it, but BE CAREFUL!
  Reply With Quote
Old 10th February 2012, 10:43 PM   #14
diyAudio Member
 
Join Date: Jun 2010
thank you
  Reply With Quote
Old 12th February 2012, 08:08 PM   #15
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Good luck, jck. I hope things work out, but I can't promise. You should use an ISOLATED screwdriver, (you can make one, yourself with some tape wrapped around the shaft), to protect you from bumping the wrong component. Usually there are 2 pots in series, why I do not know.
  Reply With Quote
Old 1st March 2012, 03:59 AM   #16
diyAudio Member
 
Join Date: Nov 2009
Location: Helena, MT
Like John says, do use an insulated driver and don't press too hard as the pots are somewhat fragile. He is also correct in stating that there are 2 pots in series. Adjust TVR1 which is the idle bias adjust and set it for 4mV(+/-1mV) DC on your voltmeter with the leads across one of the .22 ohm emitter resistors. I would let the amp idle for at least 30 minutes before doing this. The HCA-3500 amplifier also has a dynamic bias adjust and you set TVR3 to 18mV(+/-2mV) DC while applying an audio signal (music will do). After removal of the audio signal, it will take a couple of minutes for the bias to drop back down to idle. I have seen a number of HCA-3500s with the dynamic bias around 40-50mV and the heatsinks are quite hot.
  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 05:24 AM
Parasound HCA-1000a Bias Circuit Correct?? birdyman Solid State 17 4th January 2012 09:31 PM
Parasound HCA-3500 Modifications / Upgrades dcmartinpc Solid State 2 25th October 2010 08:52 PM
Help modifying HCA-3500 ironhardware Solid State 14 11th December 2008 11:38 PM
Parasound HCA-3500 USA to UK power supply Abe Solid State 4 29th November 2004 06:56 AM


New To Site? Need Help?

All times are GMT. The time now is 02:45 PM.


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