P3A turn on current surge - 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 6th April 2003, 03:14 AM   #1
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Default P3A turn on current surge

Ive built a P3A and when tested on the bench with a variac it powers up just fine. When I connect the speakers and try to power up there is a huge AC current draw that looks like a short.
Unhooking either of the speakers allows me to power up as it would with no speakers. Once the voltage is up and the single channel is playing I can connect the second speaker and everything sounds fine. It seems that the current draw at startup is keeping the voltage from getting high enough to turn on the transistors, however I dont seem to be able to get ahead of the current draw enough to raise the voltage?

Any ideas would be appreciated.

Should I just cross my fingers and twist that knob?
  Reply With Quote
Old 6th April 2003, 03:38 AM   #2
diyAudio Member
 
Join Date: Aug 2002
Location: Farmington, CT
Send a message via AIM to Mattyo5
Variac is a good idea....um...but if you do turn the knob and cross your fingers...please get pictures! :-P

You might wanna get some simple resistors at the outputs and see what happens there. Also...you might want to check for a short between the collector of the output transistors and the heatsinks. Hope all goes well!

-Matthew K. Olson

ps...email Rod before you power the thing up...he can help
  Reply With Quote
Old 6th April 2003, 10:14 PM   #3
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Thanks Mathew,

I may try the resistors.
I dont think its a short because it goes away once you get the voltage up. Im thinking an instabilty before the transistors are all "on". I used .39 instead of .47 ohm bias resistors and Ive e-mailed Rod to see if he thinks that is the problem.

I wont really twist and prey cause Ive had a lot of trouble getting this project going. I toasted several transistors initially possibly because it was testing fine on the bench and doing this under load.
  Reply With Quote
Old 8th April 2003, 10:23 PM   #4
diyAudio Member
 
Join Date: Aug 2002
Location: CA USA
Answering own thread,

Rod told me to set the variac to twelve volts hook the amp up and then switch on. Theres a large transient surge and then it settles. So the variacs slow power up was creating the problem.
  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
hlpe ! Turn on get big current titanchen68 Class D 113 27th March 2006 10:56 AM
Transformer surge current lawbadman Solid State 20 7th September 2003 08:47 PM
Turn on surge kills 1 2nd winding of transformer? Cradle22 Parts 10 23rd April 2003 11:22 PM
PSpice modeling, MOSFET, Turn-on Charge, Reverse drain current naula Parts 0 21st January 2003 03:00 PM


New To Site? Need Help?

All times are GMT. The time now is 10:21 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