[MRCA] Mystery Project

[scottjohnson1 at cox.net]

Keep in mind that a tungsten filament lamp has 10-12 times the resistance at normal operating temp as it does at room temperature, so can be used as a ballast/ current limiting some applications, but makes a poor dropping resistor.  If it is AC, consider using face to face Zeners rated at the voltage drop needed, if the drop is small, series forward biased diodes can be used similarly.  Make sure the current and power dissipation ratings are not exceeded.

Scott W7SVJ

 

From: mrca-bounces at mailman.qth.net <mailto:mrca-bounces at mailman.qth.net>  <mrca-bounces at mailman.qth.net <mailto:mrca-bounces at mailman.qth.net> > On Behalf Of ac2eu--- via MRCA
Sent: Tuesday, September 16, 2025 8:43 AM
To: B. Smith <smithab11 at comcast.net <mailto:smithab11 at comcast.net> >; Christopher Bowne <aj1g at sbcglobal.net <mailto:aj1g at sbcglobal.net> >
Cc: mrca at mailman.qth.net <mailto:mrca at mailman.qth.net> 
Subject: Re: [MRCA] Mystery Project

 

Subbing the filaments with bulbs is a tricky proposition. They have to have the same current rating as the tube or the string voltage will be out of balance. 

Ever see that old trick electricity question about to bulbs in series? One is a 40 watt and the other is a 100 watt. which will be brighter?

 

On Tuesday, September 16, 2025 at 06:48:02 AM EDT, Christopher Bowne < <mailto:aj1g at sbcglobal.net> aj1g at sbcglobal.net> wrote: 

 

 

If you have 572Bs they are plug and play subs for 811s - just have a hjgher plate dissipation rating.  I’ve been running a pair of them in my ART-13, removed from my OOC SB-200 amp since I lost an 811 snd didn’t have a spare at the time.

 

73 de Chris AJ1G

 

Sent from my iPhone





On Sep 15, 2025, at 22:51, B. Smith via MRCA < <mailto:mrca at mailman.qth.net> mrca at mailman.qth.net> wrote:

 

I was running short of 811s and operate primarily CW.
Subbed light bulbs for the tubes to keep the 813 lit.
k4che

<k4chekeyer.gif>



 <http://k4che.com/ART-13%20WO%20811s/ART-13%20Without%20811%27s.htm> http://k4che.com/ART-13%20WO%20811s/ART-13%20Without%20811%27s.htm

<bulb sub.JPG>

 

<bulb sub.JPG>

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