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
----- Original Message ----
From: "amps-request@contesting.com" <amps-request@contesting.com>
To: amps@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@stny.rr.com>
Subject: [Amps] Two HF amps for sale
To: <amps@contesting.com>
Message-ID: <565AB0FCEC784418BDE5729085EED0DB@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@onetel.net>
Subject: Re: [Amps] 8171/4CX10000D negative screen current?
To: 'AMPS' <amps@contesting.com>
Message-ID: <4E874180.607@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?
------------------------------
Message: 3
Date: Sat, 1 Oct 2011 11:51:24 -0500
From: "Joe Brown" <joe.brown@gordmans.com>
Subject: [Amps] Alpha 99 warmup timer problem
To: <amps@contesting.com>
Message-ID:
<48CF39A0587D1849AF9EB3A9A07FE4E70DDBF21E@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@g3xaq.net>
Subject: Re: [Amps] 8171/4CX10000D negative screen current?
To: amps@contesting.com
Message-ID: <4E885A3E.1000602@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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