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

Instruments and Amps Everything that makes music, Especially including instrument amps.

Sudden tube failure?
Sudden tube failure?
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 30th January 2018, 01:15 PM   #11
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
 
Tubelab_com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Most agree that the tube is operating near the meltdown zone at idle.

Quote:
299V x 0.057A = 17Watts. That is there even before there is a guitar signal present.
But only one pointed out the obvious.

Quote:
and the small core may saturate, so it would be a more difficult load at bass frequencies.
Turn off the lights in the room and observe the output tube. Is there any glow coming from the screen grid wires at idle......Then plug in the bass dial it up to 11 and thump away for a while.....it there a glowing grid now? Does the glow coincide with the loud, or the silence?

A class A amp will burn the most power in the output tube during silence. It cools off when putting out power....but not if it's OPT is saturating

If you like the sound this way, just be prepared to replace the tube more often.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 30th January 2018, 05:05 PM   #12
6A3sUMMER is offline 6A3sUMMER  United States
diyAudio Member
 
Join Date: Jun 2016
6V6dude,

Take a look at the plate of the one that broke; if it sagged you might be able to see that.
But it is more likely that the screen grid sagged, and you will not be able to see that, unless you take the tube apart very carefully.

As I suspected, you were willing to let the tube life shorten, to get the kind of sound you wanted. That is a valid design criteria for guitar amps.
A fisherman may use a very low test line in order to see if he can land the big fish by playing him. If the line breaks, he is willing to replace the line, and try playing the fish next time.
  Reply With Quote
Old 31st January 2018, 04:47 AM   #13
6V6dude is offline 6V6dude  Australia
diyAudio Member
 
Join Date: Sep 2014
I remember when I was building it, it didn't have that saturated grunt I wanted at more "normal" values so I pushed the limit to get the tone. It's kind of like a car with big turbo on it, fast but shorter lifespan.
  Reply With Quote
Old 31st January 2018, 12:50 PM   #14
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
 
Tubelab_com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
It's kind of like a car with big turbo on it, fast but shorter lifespan.
Been there.....raced that. I planned on a teardown every year, but the usual suspects were OK (turbo itself, rings, bearings, valves and valve seals). The real wear items were the timing belt, alternator, and air conditioner clutch. None of these liked being run at 7200 RPM on a motor designed for 5500 max. I also killed a transaxle just about every year.

You might experiment with a resistor in series with the screen grid. I have found that it has little affect on the tone when the amp is NOT pushed into hard clipping, but a big effect on the tone at the edge, and into clipping. Also try wiring the preamp tube's B+ supply after all or part of this resistor, with a small bypass cap.....it's value affects sag and recovery time.

What works for you is all about how you play, and the sound that you like.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 31st January 2018, 01:00 PM   #15
20to20 is offline 20to20  United States
diyAudio Member
 
Join Date: Jun 2010
Location: W-S, NC
Quote:
Originally Posted by 6V6dude View Post
I remember when I was building it, it didn't have that saturated grunt I wanted at more "normal" values so I pushed the limit to get the tone. It's kind of like a car with big turbo on it, fast but shorter lifespan.
Try a 7189. Might never have to replace it.
  Reply With Quote
Old 31st January 2018, 04:58 PM   #16
6A3sUMMER is offline 6A3sUMMER  United States
diyAudio Member
 
Join Date: Jun 2016
Thanks for this thread!!
I am learning about guitar players, and their amplifiers.
A far cry from Hi Fi amps.

I might like to build a small guitar amp someday, but know I would be like a novice swimmer in the middle of the Pacific.
  Reply With Quote
Old 31st January 2018, 05:34 PM   #17
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Sudden tube failure?
Relocated to Instruments & Amps, home to all things guitar related.
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 2nd February 2018, 09:55 AM   #18
Kay Pirinha is offline Kay Pirinha  Germany
diyAudio Member
 
Kay Pirinha's Avatar
 
Join Date: Oct 2011
Location: Somewhere in Germany
Quote:
Originally Posted by 20to20 View Post
Try a 7189. Might never have to replace it.
...or the much cheaper Russian 6P14P-EV...
__________________
"Bless you, Sister. May all your sons be bishops." (Brendan Behan)
  Reply With Quote

Reply


Sudden tube failure?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube failure ChurritoTierno Instruments and Amps 4 30th December 2017 10:00 PM
Tube rolling causes failure... Zap Tubes / Valves 10 3rd August 2008 03:04 AM
Tube Failure jwatts Tubes / Valves 11 12th February 2005 06:54 AM
Philips CD650 sudden failure! homer09 Digital Source 22 21st May 2004 08:40 AM
Tube failure Christopher Tubes / Valves 47 30th May 2003 03:35 AM


New To Site? Need Help?

All times are GMT. The time now is 08:18 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki