On 27 Feb 2023, at 17:18, Paul Bicknell <admin@...> wrote:

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Hi thank you for the return Emails

I will do a frequency sweep but we are talking down by several ?Dbm at 100 Mhz

I am 99.9 % convinced it is a problem with the series cap

Regards Paul

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From: [email protected] [mailto:[email protected]] On Behalf Of Patricio A. Greco via groups.io
Sent: 27 February 2023 21:27
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 478A Thermistor head

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How much goes down ? Did you sweep the sensor ? The input reflection coefficient is good tho check it.?

Ing. Patricio A. Greco
Taller Aeronáutico de Reparación 1B-349
Organización de Mantenimiento Aeronáutico de la Defensa OMAD-001
Gral. Martín Rodríguez 2159
San Miguel (1663)
Buenos Aires
T:?+5411-4455-2557
F:?+5411-4032-0072

On 27 Feb 2023, at 11:24, Kenneth Harrison <bibpakak507@...> wrote:

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Low end roll could be connector or bellows cap, guessing the later, but remote diagnostic is asking for trouble. Willing to help

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On Mon, Feb 27, 2023, 7:43 AM Paul Bicknell <admin@...> wrote:

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Hi? I have a HP 478A Thermistor head that works OK above 2 Ghz but reads low below 2 Ghz

I assume there is a problem with the internal series capacitor

Has anyone had a similar fault and is there any advice on a repair

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Regards Paul

--
Ken H.