What kills an opt tranny? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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

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 31st August 2006, 07:24 PM   #1
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Default What kills an opt tranny?

Hi guys,

Been thinking about this for quite some time now. What are the causes that damages/destroys an output transformer?

If it's not a good idea to run a tube amp without a speaker, what happens inside the amp? For example, if someone accidentally trips on the speaker wire and nobody notices that one of the channels of a tube amp is running without a load, will the opt be damaged? How long does it take for this to happen? Why?

TIA,
JojoD
  Reply With Quote
Old 31st August 2006, 07:38 PM   #2
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Yes, open output can kill output transformers. Happened to me once during some testing on a DIY guitar amp.
  Reply With Quote
Old 31st August 2006, 07:41 PM   #3
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
Did you happen to remember how long it took to kill your opt?
  Reply With Quote
Old 31st August 2006, 07:45 PM   #4
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Well, I switched on and played some guitar while waiting for the tubes to warm up and the sound to appear in the speaker, but the last thing never happened... I guess it died quick and painless, when I checked the primary winding was an open circuit.
  Reply With Quote
Old 31st August 2006, 07:57 PM   #5
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
That was very quick, not enough warning to stop it from being dead. Was the opt tranny the only casualty? Power tubes ok?

Hope someone explains the forces within which causes such opt failures.
  Reply With Quote
Old 31st August 2006, 08:16 PM   #6
Danko is offline Danko  Hungary
diyAudio Member
 
Join Date: Apr 2004
Location: Hungary
I soldered directly on the output xformer's secondary a 100-200 Ohm/2W resistor, to avoid such problems.
__________________
Best regards, Danko
  Reply With Quote
Old 31st August 2006, 08:52 PM   #7
Tweeker is offline Tweeker  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Cincinnati, Ohio
Transformers are inductors, going open can cause a very high voltage to develop. This may destroy the insulation. This effect may be stronger with better cores.

A gassy tube going into runaway is another possible OPT killer.
__________________
Be sure your foil hat has a good low impedance ground.
  Reply With Quote
Old 31st August 2006, 10:01 PM   #8
wa2ise is offline wa2ise  United States
diyAudio Member
 
wa2ise's Avatar
 
Join Date: Apr 2005
Location: NJ
Another thing that can kill an output transformer is excessive plate current. Usually caused by bad biasing. Leaky coupling caps that couple from a driver's plate can misbias the control grid and make the tube turn on hard and run too much current thru the plate and thus the transformer. So replace any wax paper caps you see on sight, no questions asked, they are all bad as they are way beyond their service life today. They absorb moisture from the air, and the acid in the paper causes corrosion of the metal foil inside and thus leakage paths. Use your favorite poly-whatever caps of similar capacitence and same or higher voltage rating. No ceramic caps, they are slightly piezeoelectric and vary slightly in capacitence vs voltage across them, and introduce distortion products that you don't want in your hifi amp.
  Reply With Quote
Old 31st August 2006, 10:08 PM   #9
Tweeker is offline Tweeker  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Cincinnati, Ohio
Some people like silver micas.

High K ceramics should only see psu use.
__________________
Be sure your foil hat has a good low impedance ground.
  Reply With Quote
Old 31st August 2006, 11:47 PM   #10
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
teen-age'd male offspring kill all sorts of audio gear.
  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
Now I know what this Tranny can do Tarzan Tubes / Valves 3 8th January 2009 08:37 AM
What can I do with this tranny? ThSpeakerDude88 Chip Amps 15 28th July 2005 04:29 AM
what should I do with this tranny??? mylesmf Tubes / Valves 6 9th June 2005 12:42 AM
How to use LED with +- 25v tranny? ransom peek Chip Amps 21 29th March 2005 12:55 AM
Turn on surge kills 1 2nd winding of transformer? Cradle22 Parts 10 23rd April 2003 11:22 PM


New To Site? Need Help?

All times are GMT. The time now is 09:33 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