Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Mystery SE OPT
Mystery SE OPT
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
Thread Tools Search this Thread
Old 10th July 2006, 09:28 PM   #1
alexmoose is offline alexmoose  United States
diyAudio Member
alexmoose's Avatar
Join Date: Mar 2006
Location: Michigan
Default Mystery SE OPT

hey guys, I bought a Hi-Fi at a thrift store a couple of months ago that is El84 SE I am pretty sure that they are triode strapped, however I am not certain. I want to know what primary resistance is on this OPT, is there anyway to find this out short of an educated guess?

these are small transformers, so probably 2-3 watt power handling

I know that the secondary resistance is 8 ohms

any help would be wonderful

  Reply With Quote
Old 10th July 2006, 09:38 PM   #2
Yvesm is offline Yvesm  France
diyAudio Member
Yvesm's Avatar
Join Date: Jul 2004
Location: Ardeche
Disconnect all wires from the amp,
Tie the primary on a 117Vac mains wall socket,
Measure the secondary voltage, so you'll know the voltage ratio.
Square it to obtain the impedance ratio and multiply by 8 to have the reflected primary impedance.

Put hands aways when using mains !

  Reply With Quote
Old 10th July 2006, 09:43 PM   #3
alexmoose is offline alexmoose  United States
diyAudio Member
alexmoose's Avatar
Join Date: Mar 2006
Location: Michigan
The amplifier is in no working conidition right now, could I just apply a small AC voltage to one side to figure out the ratio?
  Reply With Quote
Old 11th July 2006, 01:20 AM   #4
Tom Bavis is offline Tom Bavis
diyAudio Member
Tom Bavis's Avatar
Join Date: Jun 2002
Location: Macedon NY
5K : 8 Ohms is 625 :1 square root is 25 : 1 voltage ratio. 7K : 3.2 Ohms is 2200 : 1 , or 46 : 1 voltage ratio.
  Reply With Quote
Old 11th July 2006, 01:29 AM   #5
wrenchone is offline wrenchone  United States
diyAudio Member
wrenchone's Avatar
Join Date: Feb 2004
Location: Silicon Valley
This is essentially what the previous poster was saying, but I would not be so daring as to apply the full mains voltage across the transformer primary. A safer approach would be to unsolder all the transformer leads, noting (and labeling) which are primary and which are secondary.

You can then carefully apply AC voltage to the primary using a variac (10-20V p-p), and measure the input and output voltages using an AC voltmenter. For complete safety, one could do the same thing using a function generator.

With a function generator, one could also safely use an oscilloscope to look at both the amplitude and phase relationship of the input and output signals so that you can determine the winding polarities, an important thing to know if you're planning to use feedback with your amplifier (though you'd find out soon enough if the transformer phasing was wrong when the amplifier bursts into oscillation).
  Reply With Quote


Mystery SE OPTHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mystery RF amp spooney Car Audio 11 25th April 2008 06:14 PM
little 6.5 mystery ... oface Full Range 6 4th November 2007 11:20 PM
Transformer - mystery VA seventenths Power Supplies 10 5th September 2007 05:47 PM
Mystery woofers Doug Multi-Way 5 2nd September 2007 02:15 AM
mystery... mista2 Multi-Way 1 14th January 2005 04:20 AM

New To Site? Need Help?

All times are GMT. The time now is 02:40 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio