In a message dated 9/9/2009 3:00:34 P.M. Eastern Daylight Time,
amps-request@contesting.com writes:
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Today's Topics:
1. LK500-ZB (Paul Decker)
2. Re: LK500-ZB (Roy)
3. Re: LK500-ZB (TexasRF@aol.com)
----------------------------------------------------------------------
Message: 1
Date: Wed, 9 Sep 2009 18:36:50 +0000 (UTC)
From: Paul Decker <kg7hf@comcast.net>
Subject: [Amps] LK500-ZB
To: amps@contesting.com
Message-ID:
<802931850.144221252521410630.JavaMail.root@sz0009a.westchester.pa.mail.comc
ast.net>
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I saw a thread about LK500 and negative grid current.? Was that ever
solved?
My LK500-ZB is acting up.?? OK, I think it is my fault, the amp was on,
but in standby and I was in the shack hanging a picture and dropped the
hammer ontop of the amp (cover on and all) ?
No visible damage to the case, but now when the amp is turned on, but in
standby, the plate current reads about 200mA and the grid current is pegged
negative.? Plate voltage is lower than what it used to be, about 2600 V.??
Switching between RX/TX doesn't seem to have any affect, I can hear the
relay kick.?? One final observation, in RX, one tube starts to glow orange,
while the other stays the normal light yellow color.?
It seems as if maybe somehow the tube is internally shorted or
something.?? Ideas, suggestions..
thanks,
Paul (KG7HF)
------------------------------
Message: 2
Date: Wed, 9 Sep 2009 13:45:32 -0500
From: "Roy" <royanjoy@ncn.net>
Subject: Re: [Amps] LK500-ZB
To: <amps@contesting.com>
Message-ID: <955C343C1BC147E0ADE8A1FB8A496287@RoyPC>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
About:
"...No visible damage to the case, but now when the amp is turned on, but
in
standby, the plate current reads about 200mA and the grid current is
pegged
negative. Plate voltage is lower than what it used to be, about 2600 V.
Switching between RX/TX doesn't seem to have any affect, I can hear the
relay kick. One final observation, in RX, one tube starts to glow orange,
while the other stays the normal light yellow color...(etc.)"
My ZB had that happen several times when using Eimac tubes AND before I
installed a good in-rush protection circuit plus ridded it of parasitics.
Never has occured since (with RFP tubes). It's surely a grid - to - fil
internal short.
73, Roy K6XK
------------------------------
Message: 3
Date: Wed, 9 Sep 2009 14:54:17 EDT
From: TexasRF@aol.com
Subject: Re: [Amps] LK500-ZB
To: royanjoy@ncn.net, amps@contesting.com
Message-ID: <d57.333a4d82.37d953d9@aol.com>
Content-Type: text/plain; charset="US-ASCII"
Has anyone tried to blow a grid to cathode short with a high current pulse
of energy? Such as touching the shorted pins for an instant with a car
battery. At this point seems not much to loose by trying.
73,
Gerald K5GW
In a message dated 9/9/2009 1:46:57 P.M. Central Daylight Time,
royanjoy@ncn.net writes:
About:
"...No visible damage to the case, but now when the amp is turned on, but
in
standby, the plate current reads about 200mA and the grid current is
pegged
negative. Plate voltage is lower than what it used to be, about 2600 V.
Switching between RX/TX doesn't seem to have any affect, I can hear the
relay kick. One final observation, in RX, one tube starts to glow orange,
while the other stays the normal light yellow color...(etc.)"
My ZB had that happen several times when using Eimac tubes AND before I
installed a good in-rush protection circuit plus ridded it of parasitics.
Never has occured since (with RFP tubes). It's surely a grid - to - fil
internal short.
73, Roy K6XK
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End of Amps Digest, Vol 81, Issue 17
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