[AMPS] HA-10 Conversion to 572B Tubes

[Barry Kirkwood]

I can vouch for this:
Ken's amp looks and works better than new. Looks great alongside his mint
HRO 5T and Johnson Tx!
73
Barry
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
www.waiheke.co.nz/signal.htm
----- Original Message -----
From: <zl1aih@ihug.co.nz>
To: Bill Smith <ko4nrbs@yahoo.com>
Cc: <amps@contesting.com>
Sent: Friday, February 22, 2002 1:25 AM
Subject: Re: [AMPS] HA-10 Conversion to 572B Tubes


>
> Hi Bill
> I have restored a Heath HA-10 - it had been so severely modified and
> subsequently neglected, I had to completely strip it back to a box of
> components, nuts and bolts etc.   Luckily, I was given the original Heath
> manual, and was able to bring the amp back to almost original condition.
> I dumped the four 572Bs (3 were dead, 1 had low emission) and replaced
> them with new 811-As.    (The 866 rectifiers had already been replaced
> with a solid-state rectifier board, and HT is 1600vdc under load of
600ma.)
> IHMO, even if you already have the four 572Bs and higher voltage filter
> capacitors in your junk-box, any increased power level would put the
> existing lightweight tank circuit components under considerably greater
> stress.
> With the 811-As, I had to fit an extractor fan on the rear of the
cabinet -
> the original tiny fan was barely adequate.   For an acceptable match to
the
> exciter, I use an outboard switched pi-net circuit at the input.
> My HA-10 works fine and loafs at our 400 watt PEP limit, and that copper
> plated cabinet looks great after a re-spray.
> Good luck with your project.
> Ken, ZL1AIH
>
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>



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