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
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|