When to change tubes.

Chat about Equipment Info

Postby shakedown_04092 » Thu Dec 06, 2007 11:55 am

tigerstrat wrote:To me a microphonic tube sounds like a jagged tin can softly scratching a chalkboard with every note, or perhaps just the hardest-picked notes.


TS - check your PM
Play music, expand the mind, inspire...

"We must embrace pain and burn it as fuel for our journey" - Japanese poet Kenji Miyazawa

www.myspace.com/heavydime

Image
shakedown_04092
Senior Member
 
Posts: 1225
Joined: Sun May 22, 2005 11:51 am
Location: Portland, ME

Postby betteroffdeadnc » Thu Dec 06, 2007 11:57 am

I disagree, there is absolutly nothing wrong with tapping a tube lightly when it is running. 2ndly, the plates of a tube turning red is more an indication of a problem in the biasing circuit than in the tube. DO NOT replace a tube that is glowing red until you have checked out the bias circuit because there is a good chance the new ones will glow also. If the bias is fixed the tube may not need to be replaced, it depends on how much damage has been done. Setting the bias incorrectly will also cause the tube to conduct too much current and it will turn red. Tubes that don't need to have their bias adjusted manually still have bias circuits which can go bad.
Better Off Dead
www.betteroffdeadnc.com
www.myspace.com/betteroffdeadnc

"...Trouble ahead, a lady in red. Take my advice you’d be Better Off Dead!..."
betteroffdeadnc
Blues for Allah
Blues for Allah
 
Posts: 71
Joined: Wed Oct 31, 2007 7:02 am
Location: Raleigh, NC

Postby Laytonco » Thu Dec 06, 2007 12:20 pm

So the tin can scratching a chalkboard is not my playing? Whew!

Hee Hee.
User avatar
Laytonco
Senior Member
 
Posts: 622
Joined: Thu Mar 02, 2006 12:38 pm
Location: Denver

Postby Revv23 » Thu Dec 06, 2007 12:37 pm

betteroffdeadnc wrote:I disagree, there is absolutly nothing wrong with tapping a tube lightly when it is running. 2ndly, the plates of a tube turning red is more an indication of a problem in the biasing circuit than in the tube. DO NOT replace a tube that is glowing red until you have checked out the bias circuit because there is a good chance the new ones will glow also. If the bias is fixed the tube may not need to be replaced, it depends on how much damage has been done. Setting the bias incorrectly will also cause the tube to conduct too much current and it will turn red. Tubes that don't need to have their bias adjusted manually still have bias circuits which can go bad.


tapping a tube does not prove it's microponic. Every tube makes noise when you tap it. Even good ones. Just as every tube is already microponic. (some are just simply much more microponic hen others) Damaging or not - there is no reason to tap a tube.

Bais circuits can indeed go bad; but now we are talking about amp failure and not tube failure.

A red plated tube may indeed be a symptom of a hot bias; but there is a big difference between a red cathode and a melting tube. you could perhaps save a tube that is red plating by adjusting the bias if the problem is indeed a symptom of mis adjusted bais(if you caught it quick enough) More likely it is a symptom of tube failure.

An easy way to be prepared for tube failure is to go to a store like tubedepot.com or tubestore.com and ask for a few matched sets; they will send you tube of similar bias, so a bias adjustment isn't neccesary after a tube failure. Your backup set just needs to match the set you are using. You could foreseeably retube mid show with a setup like this. Note - i would still recommend re-biasing later as no set of tubes are truly equal, but it should be close enough that you can play the show with good sound still.

To the poster that asked what red plate/ microponic sounds like - someone already answered microponic; but a red plating tube will typically have much more distortion then usual, also your amp will be running extremly hot. Remember - an orange glow is completly normal, as well as blue glows - but red is bad.
Revv23
TC
TC
 
Posts: 32
Joined: Wed Nov 28, 2007 6:26 am

Previous

Return to Grateful Dead Equipment Discussion

Who is online

Users browsing this forum: Bing [Bot] and 5 guests