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From: rbl@nitrex.UUCP
Newsgroups: sci.electronics
Subject: Re: Power Supplies for Tube Circuits.
Message-ID: <487@nitrex.UUCP>
Date: Mon, 13-Jul-87 09:42:09 EDT
Article-I.D.: nitrex.487
Posted: Mon Jul 13 09:42:09 1987
Date-Received: Thu, 16-Jul-87 01:06:15 EDT
References: <12887@rose.UUCP> <8240@utzoo.UUCP> <485@jetsun.weitek.UUCP> <622@neoucom.UUCP>
Reply-To: rbl@nitrex.UUCP ( Dr. Robin Lake )
Organization: The Standard Oil Co., Cleveland
Lines: 41

In article <622@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes:
>
>  .....
>
>
>The high gain preamps were also usually isolated from the chassis
>by rubber or springy metal strips.  The idea was probably to combat
>microphonics from picking up vibrations of the fan.  (Quite a big
>fan was necessary to cool down a 551 with its complement of 111
>tubes! -- and it had a separate power supply with about a dozen
>more tubes for regulating all voltages).  Shock mounting the amp
>would probably be useful in combating feedback from the speakers.
>
I've been told that the policy at Tektronix was that a 'scope should 
survive a fall from
a 3 foot high table onto a concrete floor!  The springies etc. helped
the equipment fulfill this goal.

>One thing that has puzzled me is that some Tektronix plug-ins have
>flat rubber coated resistors.  I've wondered what the purpose of
>doing so was.  I've never seen any references as to why.
>
From the fuzzy dark reaches of my mind, I recall this resistor configuration
had something to do with reducing the inductance of the resistor.  Thick-film
technology, as I recall.
>
>
>Hope this was of some use.
>Bill
>(wtm@neoucom.UUCP)

There is an ART and there is a SCIENCE.  VERY occasionally, a for-profit
organization can afford to bring the state-of-the-art along with an
excellent appreciation of the science and actually produce a OPRODUCT
with the best of both!

Rob Lake
(rbl@nitrex.UUCP)

Disclaimer:  This in no way reflects any opinion of my employer nor any
knowledge gained while in my current employment.