[Boatanchors] Diode replacements for 866 tubes, ratings needed ?

[David Knepper]

Back in the "fun" days of ham radio (1950's-1970's) - many homebrewers 
constructed power supplies for their amplifiers using discarded T.V. 
transformers in a voltage doubling circuit.

I am often left to wonder why folks on this list are not referring to the 
ARRL Handbooks of that era??

Before expressing an "opinion,"  it might do all of some good in terms of 
authenticity to give a citation, that is, if you know what I am talking 
about.


David Knepper - W3CRA/W3ST
Collins Radio Association
www.collinsradio.us (new)
Join the CRA today
-----Original Message----- 
From: Rob Atkinson
Sent: Wednesday, November 12, 2014 10:19 PM
To: Rick Poole WA1RKT
Cc: Boat Anchors List
Subject: Re: [Boatanchors] Diode replacements for 866 tubes, ratings needed 
?

You have to be careful making changes to a power supply designed with a
full wave rectifier and center tap secondary.  The old iron especially is
not made to have the CT floated above ground with the entire secondary
always working with a full wave bridge rectifier.   Some plate supply
transformers like the UTC CG series around 1960 and later could be used
with CT grounded or floating above ground.  I'd bet Heath being cheap, used
a transformer made only for the stock power supply design.   There are hams
who not knowing any better fried old power supply iron trying to double the
secondary voltage.   I almost did the same thing with a big old Thordarson
transformer (it is an easy mistake to make if you have not been warned
about it).

73

Rob
K5UJ

>> If you eliminate the choke that would solve those
> >> high spike problems but then the transformer would
> >> be putting out too much voltage for the 811A's.
>
> I was considering doing that, and converting the amp to use only 572Bs at
> more nearly their rated power than is normally done in 811A amps in which
> people use 572Bs.  If I could get some decent 572Bs I might have done 
> that,
> but those don't seem to be on the horizon.  At least I can still get some
> NOS Cetron 811A tubes, for now at least.
>
> There's plenty of room in there to just convert the thing to use a single
> 3-500, and I haven't yet completely rejected that notion.  I need another
> 811A/572B amp like I need a hole in the head.
>
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