[Amps] RE: Alpha 87A Problems Solved
Dick Green WC1M
wc1m at msn.com
Sun Feb 29 14:50:33 EST 2004
Andy,
I would keep after Crosslink for a description of exactly what they did to
"fix" the problem. You may be right that they just disabled fault 17 or
increased the tolerance. If so, that would be nice to know. I don't think
you can assume that the Kenwood is not still putting out spikes and that the
87A is safe from those spikes -- unless Crosslink says so.
On the input problem, first thing to do is make sure your coax link between
the rig and 87A is at least six feet long. My 87A came with a coax link for
this purpose. At one time I replaced it with a different length and had all
sorts of problems with high input VSRW. I vaguely remember problems with 15m
especially. I took the amp apart, examined the input network, did all sorts
of troubleshooting -- to no avail. I don't remember what caused me to go
back to the Alpha-supplied coax link, but that solved the problem. Since
then, I've successfully used other links, but always over six feet. I seen
to remember something in the manual about that length.
I'm virtually certain that I was using a 950 at the time! Have never had
input VSWR problems with Yaesu and Ten Tec rigs, so maybe there's a mismatch
specific to the 950/87A/15m combination.
I don't want to unleash a whole thread on SWR, matching, etc., but I'm not
sure there's a theoretical difference between using a coax stub or a
matching network to fix the problem. However, it's certainly possible that
the 87A input network could be damaged while the 950 is autotuning. For
example, when you do a band change, the 950 will have to retune itself. But
the 950 reduces power to something like 20W during tuning, doesn't it? If
so, that should be safe. In any event, I'm never comfortable with using a
tuner with an amp, so I would try some different coax lengths and/or test
the input with a non-Kenwood rig.
BTW, since the 87A bypasses the input network on receive, the 950's tuner
won't be set correctly on receive anyway. Not to worry, for two reasons: 1)
most rigs do not keep the tuner in line when switching over to receive (I
believe that's true of the 950), and 2) even if the tuner stayed in line you
wouldn't hear any difference between tuner in or out on receive.
73, Dick WC1M
> Hi All,
>
> If any of you have been following my ordeal with CrossLink
> and the Alpha 87A fault code 17, the problem has been solved.
> After a month visit back to the factory Glenn and company
> have found the problem and the amp is apparently working as
> advertized. At least it tunes up on all bands and I have not
> had a re-occurring fault code 17 since putting it back in
> service. Since Alpha's communication is very limited, I do
> not know what they found. For all I know they deactivated
> code 17 so it would not get in the way. :) For those who
> thought that the Kenwood's were causing spicks, they are just
> fine and cause no such problems. That may have been a problem
> on older Alpha's and pin diodes but it is not the case with
> this 87A. The Alpha is happy with what the 950 SD and TS 2000
> deliver and I have not seen a fault 17 since it has been repaired.
>
> CrossLink needs to work on their communication skills
> however. Getting a response from them is difficult at best.
> Glenn was good at first but three emails for status reports
> have gone unanswered.
>
> Bottom line, when the Alpha 87A works it's great, people know
> you are there and the signal is clean.
>
> One question remains: CrossLink states not to use the
> automatic antenna tuner with the amp because it will take out
> the input VSWR pin diodes: however, I can not generate full
> output power without tuning the 950 into the 87A so that the
> 950 is looking in to a very low SWR and then the Alpha will
> put out full power. Otherwise the input SWR will >1.5 etc and
> the 87A will not put out full power even when drive power is
> increased to over 50 watts. This happens up on 15 meters. The
> Thur/Auto button on the 950 must also be in Auto mode for
> full power to be generated. The 950 should see a 50 ohm load
> when looking into the 87A and not need to be tuned so I am
> confused on this issue. On receive the 950 needs to tune the
> input for best reception so it seems that deactivating the
> automatic antenna tuner is not what you want.
>
> Any thoughts from the Alpha experts?
>
> 73 Andy WW7A
>
> -----Original Message-----
> From: amps-bounces at contesting.com
> [mailto:amps-bounces at contesting.com]On
> Behalf Of amps-request at contesting.com
> Sent: Friday, February 27, 2004 8:28 PM
> To: amps at contesting.com
> Subject: Amps Digest, Vol 14, Issue 41
>
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> Today's Topics:
>
> 1. Re: plate supply ratings and thoughts (on4kj)
> 2. for sale GU74B (Marc Wullaert ON4MA)
> 3. Re: 2 x 8877 (R.Measures)
> 4. Re: plate supply ratings and thoughts (R.Measures)
> 5. Re: Grounded B+ amplifier (R.Measures)
> 6. Re: 2 x 8877 (Phil Clements)
> 7. Re: Emtron DX-3 (Harold B. Mandel)
> 8. Re: Grounded B+ amplifier (Ian White, G3SEK)
> 9. grounded anode RF (John T. M. Lyles)
>
>
> ----------------------------------------------------------------------
>
> Date: Fri, 27 Feb 2004 17:35:11 +0100
> From: "on4kj" <on4kj at skynet.be>
> To: "Uwe Egen" <Uwe.Egen at t-online.de>,
> "Partain, Chuck" <Chuck_Partain at Maxtor.com>
> Cc: amps at contesting.com
> Subject: Re: [Amps] plate supply ratings and thoughts
> Message-ID: <004901c3fd4f$ab4b7a40$ed71c950 at hermansjos>
> References: <1Awdpl-0b89S50 at fwd04.sul.t-online.com>
> Content-Type: text/plain;
> charset="iso-8859-1"
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>
> And not to forget the transfert resistance of the used rectifiers.
>
> Jos
> ----- Original Message -----
> From: "Uwe Egen" <Uwe.Egen at t-online.de>
> To: "Partain, Chuck" <Chuck_Partain at Maxtor.com>
> Cc: <amps at contesting.com>
> Sent: Friday, February 27, 2004 9:58 AM
> Subject: Re: [Amps] plate supply ratings and thoughts
>
>
> > Hello Chuck,
> > The voltage drop at full load will be in the range 5 to
> 10 percent depending
> > on dropping input Line Voltage and design of transformer.
> > Some people explain this only with input and output
> resistance of windings
> > but it's only part of the game. Coupling between primary
> and secondary
> > is important too.
> > Greetings, Uwe, DL9NC
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
>
>
> ------------------------------
>
> Date: Fri, 27 Feb 2004 17:57:01 +0100
> From: "Marc Wullaert ON4MA" <marc.wullaert3 at pandora.be>
> To: <amps at contesting.com>
> Subject: [Amps] for sale GU74B
> Message-ID: <015901c3fd52$b8c6fca0$6501a8c0 at on4ma>
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> charset="iso-8859-1"
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>
>
> New military russian GU74B - 80?
>
> Socket SK3 - 20?
>
>
> 73
> marc on4ma
>
>
>
>
> ---
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> To: Steve Thompson <g8gsq at ic24.net>
> Subject: Re: [Amps] Grounded B+ amplifier
> References: <p7bs30pj3g8gm9vlj5von370ts7shu2rc9 at 4ax.com>
> <200402270858.53954.g8gsq at ic24.net>
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>
> Steve Thompson wrote:
>
> >On Thursday 26 February 2004 17:33, Bill Turner wrote:
> >
> >
> >>Years ago I recall reading about an amplifier where the B+
> supply was
> >>grounded and the cathode was "hot" with the B- supply. I'm
> wondering
> >>if that might have some advantages for high power amplifiers.
> >>
> >>Specifically, the pi-network output could be simplified by
> eliminating
> >>the plate choke. Here's how the output would look:
> >>
> >>http://www.dslextreme.com/users/teeaye/B+.jpg
> >>
> >>Believe it or not, this is a pi-network output circuit,
> just redrawn.
> >>The same component values would be used as with a conventional
> >>circuit.
> >>
> >>
> >Doesn't it do a lovely job of offering an alternative
> insight into how
> >a pi network matches between the antenna and plate. The load
> control is
> >the
> lower
> >capacitor and provides a variable 'tap' up and down the
> tuned circuit.
> >
> >Steve
> >_______________________________________________
> >
> This looks like a nifty alternative for cooling the 2 x
> gi7b's i've been scratching possibilites for on paper. Have a
> big heat sink for SCR's and with anode grounded can
> incorpporate it into the rear of the enclosure making a
> smaller box than would be required if the thing were kept
> insulated from the box. -bob
>
>
>
> ------------------------------
>
> Date: Fri, 27 Feb 2004 09:37:11 -0800
> From: R.Measures <r at somis.org>
> To: "P. Coppin" <copa054 at cira.it>, " AMPS" <Amps at contesting.com>
> Subject: Re: [Amps] 2 x 8877
> Message-ID: <20040227173750.10703319449 at dayton.akorn.net>
> Content-Type: text/plain; charset="US-ASCII"
> MIME-Version: 1.0
> Precedence: list
> Message: 3
>
>
>
> >
> >First of all, sorry for my poor english.
> >
> >I would like to know the reason why the amps manifacturers
> build linear
> amps
> >using three 3cx800a7, 2 3cx1200a7, one 3cx3000a7 and ruskies
> but no one
> >build a linear amplifire with 2 3cx1500a7 (8877) such as the
> Alpha sx.
> >What problems they could have ?
>
> ** Paul -- 2, 8877s cost about the same as a Svetlana 8170.
> 8877s are more delicate, and they require at least a
> 180-second warmup. 8170s are good to go in under 1-second.
> The input circuit for an Class AB1 8170 is easier to make and
> the power out is c. 4x as great.
> >
> >73
> >Paul i8ixo
> >
> >
> >_______________________________________________
> >Amps mailing list
> >Amps at contesting.com http://lists.contesting.com/mailman/listinfo/amps
> >
> ------------------------------
>
> Date: Fri, 27 Feb 2004 09:37:12 -0800
> From: R.Measures <r at somis.org>
> To: "Uwe Egen" <Uwe.Egen at t-online.de>,
> "Partain, Chuck" <Chuck_Partain at Maxtor.com>
> Cc: AMPS <amps at contesting.com>
> Subject: Re: [Amps] plate supply ratings and thoughts
> Message-ID: <20040227173750.2B152319480 at dayton.akorn.net>
> Content-Type: text/plain; charset="iso-8859-1"
> MIME-Version: 1.0
> Content-Transfer-Encoding: quoted-printable
> Precedence: list
> Message: 4
>
>
>
> >Hello Chuck,
> >The voltage drop at full load will be in the range 5 to 10 percent
> >dependi=
> ng
> >on dropping input Line Voltage and design of transformer.
> >Some people explain this only with input and output resistance of
> >windings but it's only part of the game. Coupling between
> primary and
> >secondary is important too.
>
> ** Good point, however, this is mostly a factor in
> conventional core transformers. For a Hipersil=AE core
> transformer, coupling loss is a minor=
>
> factor.
>
> >Greetings, Uwe, DL9NC
> >
> >
> >_______________________________________________
> >Amps mailing list
> >Amps at contesting.com http://lists.contesting.com/mailman/listinfo/amps
> >
> ------------------------------
>
> Date: Fri, 27 Feb 2004 09:37:11 -0800
> From: R.Measures <r at somis.org>
> To: "Steve Thompson" <g8gsq at ic24.net>, " AMPS" <amps at contesting.com>
> Subject: Re: [Amps] Grounded B+ amplifier
> Message-ID: <20040227173750.1E2CE31947A at dayton.akorn.net>
> Content-Type: text/plain; charset="US-ASCII"
> MIME-Version: 1.0
> Precedence: list
> Message: 5
>
>
>
> >On Thursday 26 February 2004 17:33, Bill Turner wrote:
> >> Years ago I recall reading about an amplifier where the B+
> supply was
> >> grounded and the cathode was "hot" with the B- supply.
> I'm wondering
> >> if that might have some advantages for high power amplifiers.
> >>
> >> Specifically, the pi-network output could be simplified by
> >> eliminating the plate choke. Here's how the output would look:
> >>
> >> http://www.dslextreme.com/users/teeaye/B+.jpg
> >>
> >> Believe it or not, this is a pi-network output circuit,
> just redrawn.
> >> The same component values would be used as with a conventional
> >> circuit.
> >Doesn't it do a lovely job of offering an alternative
> insight into how
> >a pi network matches between the antenna and plate. The load
> control is
> >the
> lower
> >capacitor and provides a variable 'tap' up and down the
> tuned circuit.
> >
> ** Indeed, Steve, indeed. It also might help folks
> understand why such a circuit resonates c. 10% lower than the
> operating frequency.
> ------------------------------
>
> Date: Fri, 27 Feb 2004 12:41:29 -0600
> From: "Phil Clements" <philk5pc at tyler.net>
> To: "P. Coppin" <copa054 at cira.it>, <Amps at contesting.com>
> Subject: Re: [Amps] 2 x 8877
> Message-ID: <00b701c3fd61$50e759e0$d6094c42 at Phil>
> References: <BLENJMKFILLGODMMLAFMKECEDLAA.copa054 at cira.it>
> Content-Type: text/plain;
> charset="iso-8859-1"
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7bit
> Precedence: list
> Reply-To: Phil Clements <philk5pc at tyler.net>
> Message: 6
>
> > I would like to know the reason why the amps manifacturers
> build linear amps
> > using three 3cx800a7, 2 3cx1200a7, one 3cx3000a7 and
> ruskies but no one
> > build a linear amplifire with 2 3cx1500a7 (8877) such as
> the Alpha sx.
> > What problems they could have ?
>
>
> Probably because a pair of 8877's is not near as cost
> effective (dollars per watt) as several other choices.
> Now that 8877's can be rebuilt for c. $450, this helps a
> bit.
>
> My philosophy on amp design has always been to select a
> SINGLE tube that will run reasonably cool at the desired
> power level.
> I have no idea why amateur amp manufacturers stuff 3-4 tubes
> in a box when one will do. Perhaps this lulls the "newbies"
> into thinking that only one tube at a time will need
> replacing. Rarely is the case, as the set should be fairly
> matched so that the load will be as equally divided as
> possible. Selecting a tube that is rebuildable is certainly
> easier on the wallet in the long run.
>
> (((73)))
> Phil, K5PC
>
>
> ------------------------------
>
> Date: Fri, 27 Feb 2004 14:35:58 -0500
> From: "Harold B. Mandel" <ka1xo at juno.com>
> To: on4ww at pandora.be
> Cc: amps at contesting.com
> Subject: Re: [Amps] Emtron DX-3
> Message-ID: <20040227.143755.2732.4.ka1xo at juno.com>
> Content-Type: text/plain; charset=us-ascii
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7bit
> Precedence: list
> Message: 7
>
> Mark,
>
> You caught me at the hotel room computer. The EMTRON DX-3
> review is not on this machine. I will send it to you on Sunday night.
>
> 1. The EMTRON DX-series of amplifiers are experiencing a breakdown
> where the plate current swings all the way to max and the
> 600 volt line
> fuses blow and there are no spare parts to fix them, or
> reasons why this happens.
>
> 2. There are ten amplifiers that have recently failed this
> way waiting for repair
> in Virginia, and they are going to be returned to their
> owners when the
> ex-Emtron repair person receives money to ship them back
> without being
> repaired.
>
> 3. The nomenclature on small electronic devices in the
> DX-series amplifiers has
> been systematically erased and sanded off to prevent
> duplication of the boards or
> non-authorized repairs or redesigns from being done.
>
> 4. The schematic diagram appearing in the owners manuals is
> tacitally incorrect.
>
> 5. The American Repair facility has been waiting for over one
> year for spare parts.
>
> 6. The Russian doorknob capacitors are KVI-3 and are not
> rated for RF Power service
> and may heat up, short circuit and explode with no warning.
>
> 7. The exhaust pulling fan is half the CFM capacity of the
> pusher fan and the buildup of
> residual air pressure in the final tube plenum means a
> drastic loss of tube cooling
> air flow at best and a destroyed output tube at worst.
>
> 8. The tube sockets are manufactured in the mid 1960's. The
> tube itself in my
> test amplifier was manufactured in 1990. The manufacturer
> does not state that
> the amplifiers are "used" or "recycled" at any point and
> this is a misrepresentation.
>
> 9. If the vacuum relay burns out it will be necessary to
> remove the controller board. No
> spare controller boards are available if the board is damaged.
>
> 10. The GU-78b tube is no longer being manufactured and when
> stock is depleted the
> amplifiers will not have any source of substitute devices.
>
> Please contact me if you require further facts about the EMTRON DX-3.
>
> Hal Mandel
> KA1XO
>
> On Fri, 27 Feb 2004 09:59:24 +0100 "Mark Demeuleneere"
> <on4ww at pandora.be>
> writes:
> > I'm about to change my trusted LK-800 for a new amp. My
> eyes fell on
> > the DX-3 from Emtron.
> >
> > Would appreciate some input from Emtron amp owners. Plus
> points, minus
> > points.
> >
> > Kindly reply to me privately, will post excerpt summary
> without call
> > signs.
> >
> > 73 - Mark
> >
> > Stories and pictures on ON4WW's travels are on the following URLs :
> > http://www.qsl.net/on4ww and http://users.pandora.be/on4ww
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> ------------------------------
>
> Date: Fri, 27 Feb 2004 17:28:14 +0000
> From: "Ian White, G3SEK" <G3SEK at ifwtech.co.uk>
> To: amps at contesting.com
> Subject: Re: [Amps] Grounded B+ amplifier
> Message-ID: <P37DurEu43PAFAB6 at ifwtech.co.uk>
> In-Reply-To: <200402270858.53954.g8gsq at ic24.net>
> References: <p7bs30pj3g8gm9vlj5von370ts7shu2rc9 at 4ax.com>
> <200402270858.53954.g8gsq at ic24.net>
> Content-Type: text/plain;charset=us-ascii;format=flowed
> MIME-Version: 1.0
> Precedence: list
> Reply-To: "Ian White, G3SEK" <g3sek at ifwtech.co.uk>
> Message: 8
>
> Steve Thompson wrote:
> >On Thursday 26 February 2004 17:33, Bill Turner wrote:
> >> Years ago I recall reading about an amplifier where the B+
> supply was
> >> grounded and the cathode was "hot" with the B- supply.
> I'm wondering if
> >> that might have some advantages for high power amplifiers.
> >>
> >> Specifically, the pi-network output could be simplified by
> eliminating
> >> the plate choke. Here's how the output would look:
> >>
> >> http://www.dslextreme.com/users/teeaye/B+.jpg
> >>
> >> Believe it or not, this is a pi-network output circuit,
> just redrawn.
> >> The same component values would be used as with a
> conventional circuit.
>
> >Doesn't it do a lovely job of offering an alternative
> insight into how
> >a pi network matches between the antenna and plate. The load
> control is
> >the lower capacitor and provides a variable 'tap' up and
> down the tuned
> >circuit.
> >
>
> Yes, I liked that too - although turning the pi-tank around seems to
> have lost its lowpass filter properties.
>
> Grounded anode is fun to think about, but I'd hate to have to
> build one.
> For every problem it solves, ten new ones appear!
>
>
> --
> 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
>
> http://www.ifwtech.co.uk/g3sek
> ------------------------------
>
> Date: Fri, 27 Feb 2004 12:56:13 -0700
> From: "John T. M. Lyles" <jtml at lanl.gov>
> To: amps at contesting.com
> Subject: [Amps] grounded anode RF
> Message-ID: <p06020402bc654f2f32f6@[128.165.34.51]>
> In-Reply-To: <20040227162502.F1A8C31953B at dayton.akorn.net>
> References: <20040227162502.F1A8C31953B at dayton.akorn.net>
> Content-Type: text/plain; charset="iso-8859-1" ; format="flowed"
> MIME-Version: 1.0
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> Precedence: list
> Message: 9
>
> I own several commercial RF systems that are configured this way, to a
> degre=
> e.
> 1) WT Larose Thermall dielectric preheater, that=20
> i test plastics, hoses, and insulators in before=20
> designing them into high power RF amplifiers. It=20
> is 90 MHz, using the Amperex 500 Watt triode. The=20
> anode is connected to the output plate on top,=20
> where you do your cooking. The filament is=20
> floated at -DC hV.
>
> 2) Continental 314R1 powerrock AM tranmitter, and=20
> for that matter, various PDM AM transmitters that=20
> used tubes in the 1980s. It has the RF tube (pair=20
> 3-500Z) floated on an insulated, heavily bypassed=20
> G10 deck. The filaments are operating at -3kV,=20
> supplied from a 'totem pole' 3-500Z operating as=20
> a class S PDM switch tube. Filament of that tube=20
> is conected to -8.5 kV DC supply. The anode of=20
> the RF tube is connected to the output network,=20
> without a blocker cap, or HV choke.
> This system is DC coupled, there is no blocker cap on the cathode side
> eithe=
> r.
>
> 73
> John
> K5PRO
>
> >Years ago I recall reading about an amplifier where the B+ supply was
> >grounded and the cathode was "hot" with the B- supply. I'm
> wondering if
> >that might have some advantages for high power amplifiers.
> >
> >Specifically, the pi-network output could be simplified by
> eliminating
> >the plate choke. Here's how the output would look:
> >
> >http://www.dslextreme.com/users/teeaye/B+.jpg
> >
> >Believe it or not, this is a pi-network output circuit, just redrawn.
> >The same component values would be used as with a
> conventional circuit.
> >
> >I see some drawbacks:=A0
> >
> >1. The filament transformer would have to be insulated for the full
> >plate supply voltage.
> >
> >2. Likewise, the grid current meter would be at the full
> plate supply
> >and would have to be carefully insulated from the chassis.
> Metal case
> >meters would not be a good idea. In fact, everything in the
> >cathode/grid circuit would have to be well insulated, such
> as the zener.
> >
> >3. Switching between standby and operate modes would require a
> >well-insulated relay, perhaps a vacuum type or reed relay.=A0
> >
> >4. The load capacitor would have it's frame grounded as
> always, but the
> >tune cap would have to be insulated on both sides.
> >
> >And there may be others, but eliminating the plate choke
> with it's nasty
> >resonances would be a big plus. While it appears at first
> glance that
> >the coupling capacitor is gone, it's function is actually
> shifted to the
> >B- connection at the cathode.
> >
> >Comments are welcome.
> >
> >--
> >Bill, W6WRT
> ------------------------------
>
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> End of Amps Digest, Vol 14, Issue 41
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