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@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of amps-request@contesting.com
Sent: Friday, February 27, 2004 8:28 PM
To: amps@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@skynet.be>
To: "Uwe Egen" <Uwe.Egen@t-online.de>,
"Partain, Chuck" <Chuck_Partain@Maxtor.com>
Cc: amps@contesting.com
Subject: Re: [Amps] plate supply ratings and thoughts
Message-ID: <004901c3fd4f$ab4b7a40$ed71c950@hermansjos>
References: <1Awdpl-0b89S50@fwd04.sul.t-online.com>
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And not to forget the transfert resistance of the used rectifiers.
Jos
----- Original Message -----
From: "Uwe Egen" <Uwe.Egen@t-online.de>
To: "Partain, Chuck" <Chuck_Partain@Maxtor.com>
Cc: <amps@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@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
------------------------------
Date: Fri, 27 Feb 2004 17:57:01 +0100
From: "Marc Wullaert ON4MA" <marc.wullaert3@pandora.be>
To: <amps@contesting.com>
Subject: [Amps] for sale GU74B
Message-ID: <015901c3fd52$b8c6fca0$6501a8c0@on4ma>
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New military russian GU74B - 80?
Socket SK3 - 20?
73
marc on4ma
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To: Steve Thompson <g8gsq@ic24.net>
Subject: Re: [Amps] Grounded B+ amplifier
References: <p7bs30pj3g8gm9vlj5von370ts7shu2rc9@4ax.com>
<200402270858.53954.g8gsq@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@somis.org>
To: "P. Coppin" <copa054@cira.it>, " AMPS" <Amps@contesting.com>
Subject: Re: [Amps] 2 x 8877
Message-ID: <20040227173750.10703319449@dayton.akorn.net>
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>
>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@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
------------------------------
Date: Fri, 27 Feb 2004 09:37:12 -0800
From: R.Measures <r@somis.org>
To: "Uwe Egen" <Uwe.Egen@t-online.de>,
"Partain, Chuck" <Chuck_Partain@Maxtor.com>
Cc: AMPS <amps@contesting.com>
Subject: Re: [Amps] plate supply ratings and thoughts
Message-ID: <20040227173750.2B152319480@dayton.akorn.net>
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>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@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
------------------------------
Date: Fri, 27 Feb 2004 09:37:11 -0800
From: R.Measures <r@somis.org>
To: "Steve Thompson" <g8gsq@ic24.net>, " AMPS" <amps@contesting.com>
Subject: Re: [Amps] Grounded B+ amplifier
Message-ID: <20040227173750.1E2CE31947A@dayton.akorn.net>
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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@tyler.net>
To: "P. Coppin" <copa054@cira.it>, <Amps@contesting.com>
Subject: Re: [Amps] 2 x 8877
Message-ID: <00b701c3fd61$50e759e0$d6094c42@Phil>
References: <BLENJMKFILLGODMMLAFMKECEDLAA.copa054@cira.it>
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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@juno.com>
To: on4ww@pandora.be
Cc: amps@contesting.com
Subject: Re: [Amps] Emtron DX-3
Message-ID: <20040227.143755.2732.4.ka1xo@juno.com>
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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@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@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
------------------------------
Date: Fri, 27 Feb 2004 17:28:14 +0000
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
To: amps@contesting.com
Subject: Re: [Amps] Grounded B+ amplifier
Message-ID: <P37DurEu43PAFAB6@ifwtech.co.uk>
In-Reply-To: <200402270858.53954.g8gsq@ic24.net>
References: <p7bs30pj3g8gm9vlj5von370ts7shu2rc9@4ax.com>
<200402270858.53954.g8gsq@ic24.net>
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Reply-To: "Ian White, G3SEK" <g3sek@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@lanl.gov>
To: amps@contesting.com
Subject: [Amps] grounded anode RF
Message-ID: <p06020402bc654f2f32f6@[128.165.34.51]>
In-Reply-To: <20040227162502.F1A8C31953B@dayton.akorn.net>
References: <20040227162502.F1A8C31953B@dayton.akorn.net>
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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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