[Amps] Boat Anchor
Steve Katz
stevek@jmr.com
Fri, 23 Aug 2002 13:11:29 -0700
Hi Joe,
It looks like an experimenter's paradise in there. I see connections and
wires going nowhere -- assume these are rendered superfluous by new and
added circuitry-? The high-Q parasitic suppressors are not a good thing,
usually. (They look like little tank coils for a 2m transmitter -- maybe
will work like them, too.)
The parasitic suppressors appear to be periliously close to the cooling fan
blades, but maybe that's just camera angle. Assume they're in proper
position when the tubes are in place.
I can't help but wonder why somebody would go to all this work to "improve"
a circuit that didn't really need any improvement. In my experience (hazy
memories of 30 years ago, but memories nonetheless) the Mark I wasn't a bad
amp, and was improved by splitting out the power supply in the Mark II
version. Assume somebody added some zener bias diode(s) for the 3-500Z's?
I think the original 3-400Z's didn't need any. Looks like the mod included
adding some tube pin connections topside of the sockets, kind of
unconventional -- wonder why that was done?
Anyway, let us know how it works!
73,
Steve WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: Joseph DiPietro [SMTP:n2uf@joeham.net]
> Sent: Friday, August 23, 2002 12:26 PM
> To: Steve Katz
> Subject: Re: [Amps] Boat Anchor
>
> makes sense. I guess I will use the variac to power it up.
>
> You will find pictures at http://www.rfengineers.com/n2uf/ there are two
> of
> each shot, one 'thumbnail' and one full-size.
>
> Joe
>
> ----- Original Message -----
> From: "Steve Katz" <stevek@jmr.com>
> To: "'Joseph DiPietro'" <n2uf@joeham.net>
> Sent: Friday, August 23, 2002 2:40 PM
> Subject: RE: [Amps] Boat Anchor
>
>
> > Joe, the reason to power it up slowly isn't just for the capacitors.
> It's
> > also a low-cost Hipot test. If there's a fault or short-circuit
> anywhere,
> > it will show up on reduced voltage but likely won't destroy the
> amplifier
> in
> > the process. On 240V, it might.
> >
> > WB2WIK/6
> >
> > "If everything seems under control, you're just not going fast enough."
> -
> > Mario Andretti
> >
> > > -----Original Message-----
> > > From: Joseph DiPietro [SMTP:n2uf@joeham.net]
> > > Sent: Friday, August 23, 2002 11:45 AM
> > > To: Steve Katz
> > > Subject: Re: [Amps] Boat Anchor
> > >
> > > I am taking pictures at the moment. Stand by and I will put them on a
> web
> > > page.
> > > The amp is presently wired for 240. All the electrolytic caps are
> new,
> so
> > > I
> > > don't think there is much reason to power it up slow.
> > > The power supply mods are not done yet, so it will be this weekend
> before
> > > I
> > > can power up.
> > >
> > > N2UF
> > >
> > > ----- Original Message -----
> > > From: "Steve Katz" <stevek@jmr.com>
> > > To: "'Joseph DiPietro'" <n2uf@joeham.net>
> > > Sent: Friday, August 23, 2002 2:19 PM
> > > Subject: RE: [Amps] Boat Anchor
> > >
> > >
> > > > Can you send the photograph? If it looks okay, I'd fire it up, but
> > > possibly
> > > > with it wired for 240V and plugging it into a 120V line, so the
> > > filaments
> > > > will barely glow and the HV will be 1/2 of normal, just to form the
> > > > capacitors and check for shorts. If it looks okay on 120V, then I'd
> hit
> > > it
> > > > with 240V and use it.
> > > >
> > > > WB2WIK/6
> > > >
> > > > "If everything seems under control, you're just not going fast
> enough."
> > > -
> > > > Mario Andretti
> > > >
> > > > > -----Original Message-----
> > > > > From: Joseph DiPietro [SMTP:n2uf@joeham.net]
> > > > > Sent: Friday, August 23, 2002 11:18 AM
> > > > > To: Steve Katz
> > > > > Subject: Re: [Amps] Boat Anchor
> > > > >
> > > > > Steve,
> > > > >
> > > > > The band switch seems to be original.
> > > > > Glen said he did not remember a great deal about the amp, so he
> did
> > > not
> > > > > say
> > > > > if it had worked or not.
> > > > > The vac cap has a 24 turn counter and gear/control attached and
> > > brought
> > > > > out
> > > > > to the front panel. the knob has a 'spinner' handle on it and
> tunes
> > > the
> > > > > cap
> > > > > quickly.
> > > > > Judging by the size of the output tank inductor I believe the amp
> was
> > > > > intended to remain in the 80-10 meter band.
> > > > >
> > > > > Joe
> > > > > N2UF
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "Steve Katz" <stevek@jmr.com>
> > > > > To: <amps@contesting.com>
> > > > > Sent: Friday, August 23, 2002 1:52 PM
> > > > > Subject: RE: [Amps] Boat Anchor
> > > > >
> > > > >
> > > > > > Joe, that sounds extremely modified!
> > > > > >
> > > > > > Glen, K9STH is a competent technician and I would trust his
> work,
> > > but
> > > if
> > > > > he
> > > > > > bought the amp already modified and didn't personally use it,
> then
> > > who
> > > > > > knows-? Did Glen say it worked okay when he had it?
> > > > > >
> > > > > > A vacuum variable in place of the original? Holy cow. Not
> really
> > > > > needed
> > > > > > for the 3kV or less the Mark I provides for the 3-400/3-500's
> > > > > (whatever).
> > > > > > That one is surprising. Sounds like possibly somebody wanted to
> > > turn
> > > > > this
> > > > > > into a higher frequency amplifier. Is the original bandswitch
> > > there?
> > > > > Is
> > > > > > the plate tank inductor original (to cover 80 meters)?
> Obviously,
> > > with
> > > > > a
> > > > > > vacuum variable in place of the original, the front panel
> markings
> > > for
> > > > > plate
> > > > > > tuning will be meaningless, and the knob will spin around a lot
> more
> > > > > than
> > > > > > 360 degrees....might make going from 10m to 80m a rather
> interesting
> > > > > band
> > > > > > change.
> > > > > >
> > > > > > WB2WIK/6
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > "If everything seems under control, you're just not going fast
> > > enough."
> > > > > -
> > > > > > Mario Andretti
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Joseph DiPietro [SMTP:n2uf@joeham.net]
> > > > > > > Sent: Friday, August 23, 2002 10:45 AM
> > > > > > > To: amps@contesting.com
> > > > > > > Subject: [Amps] Boat Anchor
> > > > > > >
> > > > > > > Hi All,
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > I am new both to this list and to HF amps, so go easy on me
> > > please!
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > I have acquired a 1960's vintage Swan Mark I amplifier. The
> amp
> > > was
> > > > > > > extensively modified prior to the mid-1970's including a
> complete
> > > > > > > rebuilding
> > > > > > > of the rf-deck. The person I bought it from told me he never
> used
> > > the
> > > > > > > amp,
> > > > > > > and it had sat in storage for at least ten years.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > A DC check of the HVPS showed at least one of the old
> (date-coded
> > > > > 1966)
> > > > > > > electrolytic caps as bad. So I replaced all of the caps, as
> well
> > > as
> > > > > the
> > > > > > > equalizing resistors and rectifier diodes.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > Before powering up the amp I would like recommendations as-to
> what
> > > > > else
> > > > > I
> > > > > > > should do. As I said, the rf-deck bears little resemblance to
> the
> > > > > > > original
> > > > > > > Mark I. The 3-400Z's have been replaced by 3-500Z's. A
> > > "penthouse"
> > > > > has
> > > > > > > been added to the top of the cabinet to increase the clearance
> > > (for
> > > > > the
> > > > > > > taller tubes, of course). Parasitic suppressors and heat-sunk
> > > anode
> > > > > > > connectors have been added (yes, those silver-plated bands
> wrapped
> > > > > around
> > > > > > > composition resistors that Mr. Measures loves so much). The
> > > tuning
> > > > > cap
> > > > > > > has
> > > > > > > been replaced with a Jennings Vacuum variable and the coil and
> > > loading
> > > > > cap
> > > > > > > do not seem to be original (I can't tell for sure since I have
> > > never
> > > > > seen
> > > > > > > the insides of an unmodified Swan Mark I).
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > I don't know who did the modifications, but someone went to a
> lot
> > > of
> > > > > work.
> > > > > > > There is a metal tag on the front panel proclaiming "Big
> Momma
> I
> > > > > Linear
> > > > > > > Amp" and it is signed "K9STH/WA4MLI/WA5STI". I contacted
> > > STH/MLI/STI
> > > > > to
> > > > > > > get some history on the modifications. He claims that he
> bought
> > > the
> > > > > amp
> > > > > > > already (rf) modified in the mid 70's. He says he added the
> > > > > "penthouse"
> > > > > > > and
> > > > > > > then sold the amp after having it less than one year.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > So experts, what should I do with this boat-anchor? Keep in
> mind
> > > that
> > > > > I
> > > > > > > am
> > > > > > > on a somewhat limited budget. New caps, diodes and resistors
> have
> > > > > cost
> > > > > me
> > > > > > > less than $30 so far, and I can't afford to spend a great deal
> > > more,
> > > > > (no
> > > > > > > vacuum relays in the budget!). This is my first HF amp. I
> hope
> > > to
> > > > > drive
> > > > > > > it
> > > > > > > with an Icom IC-751 into a G5RV antenna tuned with a very
> large
> > > > > military
> > > > > > > surplus (Collins) tuner.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > If it would help I can take some pictures of the beast and
> email
> > > them
> > > > > to
> > > > > > > the
> > > > > > > inquisitive. (Olympus C2100, 2.1 megapixels, 10to1 optical
> zoom,
> > > I
> > > > > like
> > > > > > > it
> > > > > > > very much, thank you).
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > Thanks
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > Joe DiPietro
> > > > > > >
> > > > > > > N2UF@joeham.net
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
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> > > > > >
> > > >
> >