[Johnson] Are there " good" modifications ? -yes!

[David Harmon]

There is a condition called 'cathode stripping' when B+ is applied
before the filaments are hot.
The audiophiles mostly are concerned about this. 
I'm not sure that this condition will cause a detectable performance
degradation over a lifetime or two but it does exist.

Regards

Dave Harmon
NSRCA 586
K6XYZ[at]comcast[dot]net
Torrance, Ca.

-----Original Message-----
From: johnson-bounces at mailman.qth.net
[mailto:johnson-bounces at mailman.qth.net] On Behalf Of Gary Schafer
Sent: Thursday, July 22, 2004 7:49 PM
To: Sherrill E. Watkins
Cc: Johnson at mailman.qth.net
Subject: Re: [Johnson] Are there " good" modifications ? -yes!

There is nothing wrong with applying B+ to a cold tube. It is done all 
the time in lots of equipment. Look at all the Heath equipment. Hw101, 
sb101 etc. They all have solid state supplies and the HV comes on the 
instant the switch is turned on. Cold filaments and all.

Hallicrafters made the HA6 and HA2, 6 and 2 meter transverters, that 
operated from the same power supply. All the voltages were fed to both 
units at the same time. The way one or the other was selected to operate

was to turn on the filament power on only the one you wanted to use. The

other one sat there with cold filaments and all the high voltages 
applied. Worked fine.

Small tubes do not have a problem with voltages applied before they are 
warmed up. When you get into larger tubes with over 1000 volts on the 
plate then you start worrying about that.

73
Gary  K4FMX



Johnson mailing list
Home: http://mailman.qth.net/mailman/listinfo/johnson
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:Johnson at mailman.qth.net