[Amps] Amps Digest, Vol 106, Issue 2

[John Farber]

Just an educatred guess but I'd obtain a complete schematic diagram and check 
the components making up the 3 min timer circuit as well as the relay or other 
device used to allow the amp to be driven after the timer runs to its limit. I 
do own an Alpha 99 but have never experienced the stated problem with mine. If I 
did, I would do as I suggest, above.
John



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To: amps at contesting.com
Sent: Sun, October 2, 2011 12:00:29 PM
Subject: Amps Digest, Vol 106, Issue 2

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Today's Topics:

  1. Two HF amps for sale (Bill Coleman)
  2. Re: 8171/4CX10000D negative screen current? (Dr. David Kirkby)
  3. Alpha 99 warmup timer problem (Joe Brown)
  4. Re: 8171/4CX10000D negative screen current? (Alan Ibbetson)


----------------------------------------------------------------------

Message: 1
Date: Sat, 1 Oct 2011 11:22:04 -0400
From: "Bill Coleman" <n2bc at stny.rr.com>
Subject: [Amps] Two HF amps for sale
To: <amps at contesting.com>
Message-ID: <565AB0FCEC784418BDE5729085EED0DB at Radio1>
Content-Type: text/plain;    charset="utf-8"

2KW ?Plasma Generator? /w 5CX1500 converted to 160M ?> 10M
Info here:  http://home.roadrunner.com/~n2bc/FOR_SALE_PT_AMP.htm


Harris RF-110A amp & RF124 Power Supply (2-8122?s & 2-4CX1500?s), NO TUNE 160M 
?> 10M
Info here:  http://home.roadrunner.com/~n2bc/FOR_SALE_HARRIS_AMP.htm


THX & 73,  Bill N2BC

------------------------------

Message: 2
Date: Sat, 01 Oct 2011 17:36:16 +0100
From: "Dr. David Kirkby" <david.kirkby at onetel.net>
Subject: Re: [Amps] 8171/4CX10000D negative screen current?
To: 'AMPS' <amps at contesting.com>
Message-ID: <4E874180.607 at onetel.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 10/ 1/11 03:16 PM, Alan Ibbetson wrote:
> Does the 8171 or other tubes with handles exhibit negative screen grid
> current like their much smaller 4CX250B brothers? The constant current
> curves on the data sheet suggests the 8171 doesn't suffer this anomaly,
> which would ease the design of the screen regulator.
>
> 73, Alan G3XAQ

I expect so, but have you checked the data sheet? There is bound to be that 
information in there.

There a data sheet on my web site.

Dave, G8WRB.

-- 
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?


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Message: 3
Date: Sat, 1 Oct 2011 11:51:24 -0500
From: "Joe Brown" <joe.brown at gordmans.com>
Subject: [Amps] Alpha 99 warmup timer problem
To: <amps at contesting.com>
Message-ID:
    <48CF39A0587D1849AF9EB3A9A07FE4E70DDBF21E at gmail.gordmans.net>
Content-Type: text/plain;    charset="us-ascii"

Hello,



I am trying to find out what is wrong with an Alpha 99 amplifier, when
the amplifier is turned on, the 'WAIT' LED will not shut off at the
correct time, which is supposed to be approx. 3 minutes. We have left it
sit for hours, and sometimes it will turn off after a few hours,
sometimes after a few minutes, sometimes never. 



Anyone have any ideas? I have the front cover off the amp and have tried
adjusting the R109 adjustment pot, no difference. 



Thank you, 73



Joe W0DB







------------------------------

Message: 4
Date: Sun, 02 Oct 2011 13:34:06 +0100
From: Alan Ibbetson <alan at g3xaq.net>
Subject: Re: [Amps] 8171/4CX10000D negative screen current?
To: amps at contesting.com
Message-ID: <4E885A3E.1000602 at g3xaq.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Thanks to several people who replied to me off-list. I was wrong to call 
negative screen current an anomaly, it is an expected consequence of 
some tube geometries. I have been told that in practice tubes with 
handles do not produce negative screen current. This is in agreement 
with the published constant current curves.

73, Alan G3XAQ


------------------------------

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End of Amps Digest, Vol 106, Issue 2
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