[Test-Equipment] HP 403B pegging meters

[Howard]

Maybe a Thermistor inline with that cap or meter lead??
----- Original Message -----
From: "Ron Youvan" <ka4inm at tampabay.rr.com>
To: "Discussion of Electronic Test Equipment"
<test-equipment at mailman.qth.net>
Sent: Thursday, March 13, 2008 9:06 AM
Subject: Re: [Test-Equipment] HP 403B pegging meters


> >  Here's my best guess as to what's happening.  There's a big
> > 1200 microfarad de-coupling cap in the DC negative feedback loop.
>  >  This is probably necessary in order to get the frequency response
>  > down to 5 Hz. Until it charges up (through an 8.2K resistor ) and
>  > the loop can correct itself, theres an > initial rush of current
>  > through the meter movement. I still can't account for the second
>  > 'peg', though.
>
> >  It would be interesting to know if anybody has devised a way to
>  > prevent the pegging. Perhaps using some component or trick that
>  > wasn't available back when the instrument was designed?
>
>    Disabling the "meter amplifier" (or shorting out the meter)
> until a slower capacitor is charged is trivial, but that option
> was available to the original designer.
> --
>     Ron  KA4INM - Please pay your taxes promptly our
>                   illegal aliens need the free benefits!
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