Don wrote: >That would be true only if the original rectifiers were high vacuum tube >types. With mercury vapour or xenon gas rectifiers, the voltage drop across >each tube is about 15 volts, regardless of the current. When you are >talking about 2500 or 3000 volts total on the plate, the voltage drop across >the rectifiers is insignificant.
My experience has been that solid-state stacks cause the B+ to rise more when replacing vacuum rectifiers, but it also does it to a lesser extent with mercury vapor rectifiers. I don't think I've ever done it with a xenon-filled tube. Could also be something else at play in those cases, or faulty memory, I admit. I might have upgraded filter caps at the same time, for example. In any case, your observation indicates it is even easier to do the replacement for vapor/gas tubes. Mercury vapor tubes put on a very pretty light show, so they should be used if possible. -grin- How do xenon tubes look in action? Steve WD8DAS [email protected] http://www.wd8das.net/ --------------------------------------------------------- Radio is your best entertainment value. --------------------------------------------------------- -----Original Message----- From: D. Chester <[email protected]> To: [email protected] Sent: Sun, Oct 4, 2009 4:36 pm Subject: Re: [AMRadio] AMRadio Digest, Vol 69, Issue 4 > You can expect somewhat higher voltage from the new stack than the > original tube rectifier - if that is a problem for the rig, then add a > series power resistor to simulate the internal voltage drop of the > earlier tube. So far I've only needed to do that once when the new > higher B+ exceeded the rating of the by-pass caps in the other sections > of the rig. Otherwise the rigs seemed to thrive on the higher voltage. > > Steve WD8DAS That would be true only if the original rectifiers were high vacuum tube types. With mercury vapour or xenon gas rectifiers, the voltage drop across each tube is about 15 volts, regardless of the current. When you are talking about 2500 or 3000 volts total on the plate, the voltage drop across the rectifiers is insignificant. With solid state, the voltage drop across each diode is about 0.7 volts. So if you have 20 1kv diodes series strung to give 20kv p.i.v., you will have approximately the same rectifier voltage drop that you would have with a set of MV tubes. Don k4kyv _______________________________________________________________ This message was typed using the DVORAK keyboard layout. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
