On Mon, 01 Sep 1997 12:30:32 EDT nospam4me@juno.com (Skip S Isaham)
writes:
>Hello Carl and crew,
>
>First let me mention, I sent John an offer of photo copies of the
>Heath HL-2200 manual that I have. It's pretty much the same animal as
>the SB-220/221.
>
>So now I see a lot of big bang warnings about the SB-230 posted. Since
>I have a virgin factory built unit that I've been using only on 40
>meters with no problems, I'd like to know what the story is with the
>amps' problems. I'll have a look at some of the web pages to see any
>additional info also.
>
>I'd hate to dial this thing up on another band and watch it go up in
>smoke... Other than a very noisy T/R relay, it's been a really nice
>unit.
The problem with that amp is in the grid circuit, plate circuit, power
supply and cooling; which doesnt leave much else.
Why on earth Heath floated the grid of that tube at RF I'll never know.
Those tiny little 1000 pf grid caps also break if you look at them funny.
Heath knew that amp was squirrelly, thus the resistors in the grid
circuit.
The PS needs a surge suppressor resistor, any enamelled wirewound ( not
cement) of 10-15 Ohms at 20W will suffice.
The parasitic suppressor is non existent; the first time those little
ferrite beads overheat they become junk. Rewire the plate circuit from
the RFC, tube and plate blocking cap in a conventional manner and with a
good parasitic suppressor.
The 8873 has a dissapation rating of 200W, not 400 as in the 8874.
Anything over about 500W out requires a heat sink fan. The 8873 will last
a long time at 500W not 800W as I have heard of some trying to push it.
I am not sure either about the tube ceramic seals since they receive no
cooling air.
I have a number of SB-230 bandswitches here with vaporized contacts and
Tune caps with melted plates. Something is not right in that amp.
They do make excellent and stable 6M amps once all the junk is removed.
Outputs of 450W are possible with drive levels of only 15-20W. During
stability tests with lots of cooling I have had no problems at 750W out.
>I have the original tube in operation and a spare that has the
>"better" anode material vs some of the newer productions where the
>mfgr has used a "cheaper material".
>
>Maybe someone could shed some light on the anode material difference?
Is it the plate material or just the plating? probably the same reason
as 8877's, 3CX3000's, etc.....cost reduction.
BTW, on another reflector not known for high levels of intelligence, one
chap warned that the 8873 had a deadly gas inside ! So near, yet so far.
73....Carl KM1H
>OK for now...
>73's
>Skip wv6f
>nospam4me@juno.com
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