[Milsurplus] To be 90 or not to be...

[kgordon2006]

The 90 V regulated is not strictly needed. If you review the schematic, you will find a pair of resistors that connect to the main voltage source, usually the 180V, and provide the necessary 90 volts to the detector when the regulated 90 V is missing.The stock power supply with its huge current regulator, and big VR tube is needed when the receivers were used on capital ships with their very unreliable sources of AC. Large swinging turrets tended to pull the AC voltage down.When these receivers are used in a modern home, none of that superior regulation is needed.Ken W7EKBSent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
-------- Original message --------From: "Charlie L." <mjcal79 at gmail.com> Date: 9/2/25  09:24  (GMT-08:00) To: milsurplus at mailman.qth.net Subject: [Milsurplus] To be 90 or not to be... Since the RAK/RAL has come up, what is the deal with the 90 volts?  I built a supply for my RAK which I acquired first and put in a  regulator circuit using a 90 volt reg. tube that I just happened to have, it glows orange, but the radio worked just fine with or without the 90.  My other supply for the RAL is the correct supply for it and got that from Brian KN4R.  The only problems so far after a decade or more has been replacing the 1uf caps and other large bypass caps, tubes I have found plenty of.  That one stacked cap under the chassis might be a concern, but if need be, could be subbed with individual bypasses if it ever fails.  The RAK gets its most use during the winter when I am looking for NDB's, using it or a Mackay 128XX, the RAL gets used throughout the year. Charlie in NC.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20250902/18eb1a16/attachment.html>