IM-25 problems

[Neil Morrison]

Do they use balanced transistors? Some cheaper models used one FET
only. Generally, you need to use matched pairs of transistors and in
some cases couple them thermally to balance the drifts.

NM

----- Original Message -----
From: "Edward B Richards" <zuu6k at JUNO.COM>


> Hi Guys;
>
> I have 2 of subject TVOM's. I like them because they have more
scales
> than most VTVM's; 9 voltage, 7 resistance and 11 current. The low
voltage
> scales (.5 & .15) are handy for nulling SSB carriers and
neutralizing
> transmitters during alignment. They can be battery powered, a
feature
> that I have not used yet. They also have separate switches for the
> voltage, resistance and current ranges, with a function switch to
select
> which one is being used. That way you don't have to change the
voltage
> range to read resistance, etc.
>
> The problem is that both of them drift. I have to keep taking them
apart
> and re-calibrating the functions. They also drift during the first
hour
> of use. Does anyone have a cure for this? maybe a voltage regulator
for
> the AC power supply? Anything that would make them more stable.
Thanks
> and 73.
>
> Ed Richards K6UUZ

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