[Boatanchors] VFO Drift

[David Knepper]

That is what Tony indicated to me.

Even if one were to dry the board in an oven, the dielectric properties are 
no doubt still irreversible.

Collins Radio in their early, early KWM-380, (below 50 serial numbers)  had 
to change to a different circuit board material, probably, due to the 
changes in dielectric properties.

Thanks

David Knepper, W3ST/W3CRA
Publisher of the Collins Journal
Secretary of the Collins Radio Association
www.collinsra.com
Join today
Nets: 14.263 Mhz, 1900Z, Sundays
3.805 Mhz, 2300Z, Mondays

----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "David Knepper" <collinsradio at comcast.net>
Cc: <boatanchors at qth.net>
Sent: Friday, July 09, 2010 1:37 PM
Subject: Re: [Boatanchors] VFO Drift


> FWIW, the board material had likely absorbed water, changing its
> dielectric constant, hence the frequency.
>
> Best,
>
> -John
>
> =============
>
>> I thought that I would pass this on for what it is worth.
>>
>> A friend of mine was utilizing the solid-state PTO board from a WRL Glaxy
>> V,
>> Mark II for his new homebrew transceiver project.
>>
>> Tony told me today that the problem was not the components mounted on the
>> board but the board itself.  When he mounted the components on a new 
>> board
>> made of plexiglass material, the drift problem went away.  It seems that
>> the
>> original board was the problem since it was made of some kind of phenolic
>> material.  When he even blew on the board, the frequency would begin to
>> take
>> off.
>>
>> The new PTO drifts less than 200 cycles over a period of an hours and 
>> then
>> settles down.
>>
>> Has anyone experienced a similar occurrence?
>>
>> That original material that WRL used for the PTO evidentally had lost its
>> insulation properties.
>>
>> He thought sure that it was not a component failure since he had replaced
>> everything on the old board.
>>
>> Thank you
>>
>>
>> David Knepper, W3ST/W3CRA
>> Publisher of the Collins Journal
>> Secretary of the Collins Radio Association
>> www.collinsra.com
>> Join today
>> Nets: 14.263 Mhz, 1900Z, Sundays
>> 3.805 Mhz, 2300Z, Mondays
>>
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>
>
>