DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

B+ powered before heaters. How bad was it?
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6119
Page 2 of 2

Author:  M. Gregg [ 02 Feb 2018, 09:50 ]
Post subject:  Re: B+ powered before heaters. How bad was it?

[quote="Gio"]Here is a good and entertaining read on the subject and why a standby switch is a good thing: https://peavey.com/monitor/pvpapers/Chapter6.pdf

The very interesting and argument causing "cathode stripping and poisoning".
Also links to inrush suppression.

Thanks for posting the link interesting read.

Regards
M. Gregg

Author:  Suncalc [ 02 Feb 2018, 19:42 ]
Post subject:  Re: B+ powered before heaters. How bad was it?

With modern tubes (i.e. those made after about 1945) I have always found the problem of poisoning is much more serious than cathode stripping. I have yet to document a case of cathode stripping at a B+ of less than about 1000V. Poisoning just requires the heaters to be on.

Author:  gofar99 [ 02 Feb 2018, 20:11 ]
Post subject:  Re: B+ powered before heaters. How bad was it?

Hi, I'm with Matt on this. I too have never seen it occur.

Good listening
Bruce

Author:  KochiyaYamato [ 04 Feb 2018, 17:29 ]
Post subject:  Re: B+ powered before heaters. How bad was it?

When the cathode has not reached its proper operating temperature (i.e. the cathode is not yet incandescent/glowing)
electrons are “ripped” from the barium/strontium/calcium carbonate cathode coating itself, causing a phenomenon known as “cathode stripping.”

I don't see how electorns can have physical forcse to ripp the coating off the cathode, maybe ripped off the cathode is only a imagination term on how the authour feels about doing this.
When a valve is not fully heated up, less current flows through the valve because its too cold for the electornns to flow freely, the valve internal resistance is higher, I don't see any plorbem nor damage.

this is referred to as “cathode poisoning.”
high resistance layer is gradually formed at the “interface” between the
oxide coating and the nickel cathode structure. This
layer of barium orthosilicate causes tube performance
to degrade significantly

Personally I do not beilve this, further more with many online researches I've done.
There wasn't any explantion on how the cathode posions or strips. All was said is that the cathode will strip, but how does it strip? There will be a high resistance layer but how does it form up.
Theres no reasoning and its all claims wihout any proof.

If theres any formal testing with sufficent proof on valves degrading then I will accept that.
I've accumulated more than 4000 hours on my 6z4 rectifier, more than 6000 horus on 6n4 valve. They still go perfect, no warm ups were ever used.
These valves are so reliable that I want them to be less reliable.

Author:  Soundbrigade [ 04 Feb 2018, 17:36 ]
Post subject:  Re: B+ powered before heaters. How bad was it?

Looking for answers, but this is a normal and wellknown phenomena for Nixie-tubes.

Page 2 of 2 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/