[Boatanchors] 0A2 and 0B2 in Parallel?

[Sandy]

Re: [Boatanchors] 0A2 and 0B2 in Parallel?I'm glad you found the "problem"!  I used to have a TO-9 keyer and kept it for quite some time.  I didn't recall the tubes being in parallel.

A note about this.....Using two or more cold cathode "gas" VR tubes in parallel isn't a good idea.  There will be differences between different manufacturers and electrode structure, etc. that will invariably upset the balance of additional tubes in parallel causing one tube to "hog" the current consumed.  I DO remember reading somewhere this "could" be done....BUT....only with a small limiting resistor in series with the anode lead of EACH tube. The same article/tube handbook or wherever it was warned about other caveats which I don't recall no.  Too many years ago.

If you need better regulation, best thing is to use a "pass" triode/pentode "regulator stage" with a gas diode "reference" source.  Some of the old "Handbooks" give circuits that work quite well, hold the voltage to more rigorous tolerances and over a greater current range than the simple gas "VR" tube.

In most instances the simple "VR" regulators are sufficient for most amateur applications unless you are trying to regulate a lower voltage, or voltage other than the "stock" VR tube values.

73,

Sandy W5TVW
\
  ----- Original Message ----- 
  From: eugene at hertzmail.com 
  To: jfor at quik.com ; WA5CAB at cs.com 
  Cc: boatanchors at mailman.qth.net 
  Sent: Friday, February 20, 2009 3:20 PM
  Subject: Re: [Boatanchors] 0A2 and 0B2 in Parallel?


  Ahh. You guys are of course, correct. I misread the diagram. They are providing two different voltages, +150 and +105. My bad.

  Here's the diagram of the PS if anyone is interested. 
  http://www.hertzmail.com/to-keyer/to-ps.jpg

  Eugene



------------------------------------------------------------------------------
  From: J. Forster [mailto:jfor at quik.com]
  Sent: Fri 2/20/2009 3:49 PM
  To: eugene at hertzmail.com
  Cc: boatanchors at mailman.qth.net
  Subject: Re: [Boatanchors] 0A2 and 0B2 in Parallel?


  Are you SURE they are wired in parallel? Maybe back to back ?

  Parallel makes no sense at all. They are different voltages:

  http://scottbecker.net/tube/sheets/155/0/0A2.pdf

  -John



  > Hi there. I just acquired a very nice Hallicrafters HA-1 TO Keyer. I was
  > reviewing the circuit diagram from Bama and saw in the power supply, a 0A2
  > in parallel with a 0B2.  I am assuming that they are paralleled to permit
  > more current to pass, but why not use two of the same?  What is the
  > difference between these two tubes?
  >
  > Thanks in advance
  > Eugene






------------------------------------------------------------------------------


  ______________________________________________________________
  Boatanchors mailing list
  Home: http://mailman.qth.net/mailman/listinfo/boatanchors
  Help: http://mailman.qth.net/mmfaq.htm
  Post: mailto:Boatanchors at mailman.qth.net

  This list hosted by: http://www.qsl.net
  Please help support this email list: http://www.qsl.net/donate.html


------------------------------------------------------------------------------



  No virus found in this incoming message.
  Checked by AVG - www.avg.com 
  Version: 8.0.237 / Virus Database: 270.11.1/1962 - Release Date: 02/20/09 07:26:00
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/boatanchors/attachments/20090220/e725acae/attachment.html