amp testing - 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 10th May 2002, 02:42 AM   #1
diyAudio Member
 
Join Date: Nov 2001
Location: Harlowton, MT, USA
Lightbulb amp testing

There's probably a thread or 2 about this sort of thing out there somewhere, but I couldn't find one.

Would it work to use a fan controller in place of a variac when testing amps? I don't have a variac, and the're expensive and I would have to order one which would take a week, but I could get a variable speed fan controller easily. They're about $15US and rated 600W. I've had a channel of my Leach amp done for a couple weeks, and the power supply too, but I'm afraid to test it until I get something to bring up the voltage slowly, along with some current limiting, of course. I figure if a fan controller can control an induction motor, then it could probably controll my power supply transformer, as both devices are of much the same nature.
  Reply With Quote
Old 10th May 2002, 03:02 AM   #2
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
generally speaking.... NO! alot of these devices do weird things to the mains (clip and chop) in order to drop the voltage and your amps almost certainly will not like this.
  Reply With Quote
Old 10th May 2002, 03:06 AM   #3
diyAudio Member
 
Join Date: Nov 2001
Location: Harlowton, MT, USA
Will the filter caps and transformer inductance not take care of that?
  Reply With Quote
Old 10th May 2002, 03:35 AM   #4
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
They function by hacking out part of the sine wave of the incoming AC. Your problem will be that when the AC switches on, the diodes in the rectifier will get hit with a massive rush of current as the caps attempt to charge. Even if we assume that the diodes can take it (unlikely), your current coming off the bulk caps is going to look pretty lumpy and you're going to have a lot of racket in the circuit as a result.
I know it's tempting, but I'd advise against it. Either buy a Variac or just grit your teeth and turn it on. A load resistor might be a good idea, rather than using an actual speaker...at least until you're satisfied that the amp's working properly.

Grey
  Reply With Quote
Old 10th May 2002, 03:41 AM   #5
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Also, if you are using a toroidal transformer, you may find that things get highly unpredictable as the magnetising current will not be stable.
  Reply With Quote
Old 10th May 2002, 03:46 AM   #6
diyAudio Member
 
Join Date: Nov 2001
Location: Harlowton, MT, USA
Yep, it's a 1.5kVA toroid.
  Reply With Quote
Old 10th May 2002, 03:58 AM   #7
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Either use a Variac or just plug the amp into the wall, hit the power switch and hope for the best .... dont use the fan controller ..... Just my 2 cents
  Reply With Quote
Old 10th May 2002, 11:51 AM   #8
alfsch is offline alfsch  Germany
diyAudio Member
 
Join Date: Jan 2002
Location: augsburg
Hi,
i use the best cheap solution to this: just a standard light bulb in series to the amp power input; this prevents big switch-on currents, gives safety (if the amp has a problem...) and you get some optical contol, how much power the amp is consuming; just use 2 bulbs switchable, like 40W and 200W, to be used for lower or bigger amps....and a switch to pass them, if the amp works and you make some power tests .

alf
  Reply With Quote
Old 10th May 2002, 12:29 PM   #9
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Yeah or power resistors in place of the fuses would work also but you have to ensure that the voltage is still high enough to allow correct operation of the amp.
  Reply With Quote
Old 10th May 2002, 07:43 PM   #10
diyAudio Member
 
Join Date: Nov 2001
Location: Harlowton, MT, USA
Thanks, guys
  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
DMM for Hfe testing pooge Solid State 4 29th June 2007 02:02 AM
testing FET peter pkcc Solid State 2 16th June 2001 02:40 PM


New To Site? Need Help?

All times are GMT. The time now is 01:43 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