Heath A9 amplifiers

[LBRTY4US at AOL.COM]

A late reader here.  :-)  Just got an A9B.  Noted it has a fusible
resistor in its ac supply on a separate strip not called out on that
fuzzy/bad online A9C schem, probably other changes too as you allude to.
Has a grey hammertone chassis.  If U hv that schem in electronic form I
cld use it as well.  :-)

"Museum" site calls 9C a '58, possibly the B is '57?

Did find a page of independent hobbyist tests run on many OPT's incl this
amp's 51-14, and it came out poorly - but his testbed was 6550's.  OPT has
a reflected Z of 8k using the 8z spkr tap.

Also hv had an A-10 for a long time, hv never seen a schem or specs
anywhere, M-site only has pic.  Very different from A9, 2xEL34 & 6AN8/A,
beefy horiz OPT, gold chassis w/cage, bias adj.  Refurbed 3 yrs ago (&
only bench burned-in to dummy, no listen), found selection of a hot 6AN8
critical to output pwr, went thru 6-7 NOS B4 finding a nice one, though
all tested high on TV-7-D/U.  AIRC the best was a no-name oddball.  May or
may not relate to the pwr bottles I used (late '60's NOS Sylvania-boxed
double-halo Mullards).

Any performance reviews/remarks of these amps online anywhere (yup I
searched)?  With the huge efficent cabs of the day, they prob kicked butt
with low wattage...

Frank

On Tue, 17 Feb 2004 22:53:39 -0500, Chris Campbell <clcampbl at TRAVERSE.COM>
wrote:

>I just mailed a copy of the A-9B schematic out (Heath sent it to me
>years ago).   I compared it to a fuzzy print of the A-9C schematic from
>the internet.  There was a voltage divider or something in the power
>supply of the -C that was not there on the -B.  I have not pulled my -A
>model from strorage to see what it has.  But that P.S. change was the
>only one I spotted.  There must be others.
>
>Chris Campbell
>
>Fred wrote:
>
>>I normally am interested in Heath Ham gear but the postings on the A9
series amplifiers made me pull one I have out.  What are the differences
between the A,B, and C versions.  I thought I remembered a version with a
gold chassis the same color as the W5.  I found an original book for the
A9C and it shows one of the filter caps in series with bleeder resistors
across them.  The one I have doesn't use this setup and looks totally
original underneath.
>>I found the one I own has had a pilot lamp mounted through the center
chassis hole which was normally covered with the control plate #205-
M20F161.  Unfortunately, the model number of the amp on the plate was
damaged when someone drilled a hole through it so I am not sure which
version I have.  Mine has a grey chassis.  This brings me back to the
question: Would anyone on this list have a control plate they would like
to sell?
>>
>>Thanks,
>>
>>Fred
>>WA3KIO
>>
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