[R-390] Variacs

Tue, 22 Jul 2003 14:50:06 -0400

Les & Gang:

There may not be an absolute "need", particularly for an SP-600.  If using
the 130 V. tap, that should cover 126 volts.

However, many others, like the '390's were designed with 110-115 in mind.
While 10% more is tolerable, it's not ideal or the midpoint for which the
components were chosen.  So, using a variac or buking transformer to cut it
down may contribute to longer component and tube life.

Here we have 126 volts typically, with some variation. During the summer, it
can sag as low as about 95 vac.  A variac provides the ability to provide
some boost if needed.

Not to mention that it provides yet another knob to tweak and meter to read.
(Adds "tinker-value".)

If the rectifiers have been solid stated out, you can use the variac to
bring up the receiver slowly which may help some over the long haul.  If the
26Z5W's are still in there, it's unlikely to make a difference as they don't
forward conduct until a threshold voltage is reached anyway.  (Something
like 90 volts, as I recall).

Necessary -- no.  Helpful -- maybe.  But be careful of the variacs with a
range switch, typically 0-120 and 0-140 volts nominal -- very nominal.  More
likely to be 0-130+ and 0-150+ with more typical input voltages.  Keep it on
the low range and put some tape over the switch.

Barry

----- Original Message -----
From: <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Tuesday, July 22, 2003 12:53 PM
Subject: Re: [R-390] Variacs

> That is pretty much why I do not see a need for a variac. And, on the
SP-600 series, use tap # 5 130 volts.
>
> Les Locklear
>
> In a message dated 7/22/2003 11:09:09 AM Eastern Standard Time,
<[email protected]> writes:
>
> >Dear Friends,
> >
> >As per Dave Kamp in his last post...10% tol. would
> >give you more than enough room for the top...Surely no
> >USA sources go as high as 126.5V...???
> >
> >So it may make it a bit irrel. for the 390 series..??
> >
> >Regards, John (JLAP)
> >
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