sb101,102,hw101.

[Mark Graalman WB8JKR]

  I guess its not a "bad" idea, but I can't see it.
 My line voltage is a constant 124 and I have and
continue to run lots of older gear without any
trouble. Heck, dropping the filament voltage
by even 1 volt at a 10 amp total draw is only pulling
10 watts of heat from the rig.
 Again, I have no problem with doing it but
I don't think its needed. To each their own.

Mark  WB8JKR


On Thu, 6 Feb 2003 16:59:13 -0800 Keith Rowland <k4kgw at ATTBI.COM> writes:
> People, I am not sure there is really a problem with this line
> voltage.  Most
> of the older stuff was designed to operate from 105-125 VAC.  What's
> the
> problem?
>
> Keith
>
> "Gerald C. Lemay" wrote:
>
> > Let me see if I understand this. Assuming a transformer was
> designed for
> > 110VAC input to get 12.6VAC means a ratio of 12.6/110=0.1145. So
> with
> > 125VAC line you would get 0.1145 X 125=14.32V. So if you want to
> drop the
> > heater voltage down to 12.6V, let's assume a heater current of
> about 5A.
> > To drop 1.72V at 5A, R=1.72/5=0.34 Ohm. The figures are not in
> agreement
> > with what I read but the approach is a sound one. If your line
> voltage
> > runs high (whatever that means) the proper way to adjust it is by
> > measuring the heater winding voltage. That really doesn't apply to
> me
> > because I very seldom go above 122VAC. Line voltage at my place is
> pretty
> > steady at 120VAC plus or minus a couple of volts. I've been trying
> to find
> > out if this business of higher line voltage being used with
> transformers
> > designed for lower input is factual or mythical. The transformer
> > manufacturers are not helpful. Even today you see transformer
> > specifications with primary line voltage at 115VAC! I'm not sure
> it was
> > ever intended to be a tightly controlled spec. Even tube heater
> > characteristics varied from tube to tube and it was not uncommeon
> to find
> > the actual voltage required to draw the speicifed heater current
> to vary
> > by several percent. Back in high school shop class (1967)the lab
> books
> > always specified 117VAC as being typical line voltage.
> >
> > > In a message dated 2/5/03 3:17:21 PM Eastern Standard Time,
> > > w2jjm at MSN.COM writes:
> > >
> > >
> > >> This line of equipment was designed when AC line voltages were
> much
> > >> lower than they are today. If you want a cooler running rig
> with no
> > >> loss of 6ea8 and
> > >> 6au6 tubes due to leaks and shorts the solution is easy. In
> your HP-23
> > >> power
> > >> supply install four (4) RS-271-131 one (1) ohm 10 watt
> resistors all
> > >> in parallel
> > >> in the 12.6 volt feed lead. This 0.25 ohms will bring your two
> > >> filament strings
> > >> down to mfgs specs of 6.3 vac. If there is any small imbalance
> left
> > >> you may wish to hand pick your pilot lites. Good luck.
> > >>
> > >
> > > James,
> > >
> > > You are kidding, right?  Is it April fools yet?  12.6V/.25 ohms
> = 50.4
> > > amps, or 635W.  Did you mean 10 ohms? (63.5W, nah)  Did you mean
> 100 ohm
> > > resistors? (6.35W, maybe).  Whatever the value or power drawn,
> lets not
> > > forget to make sure that the transformer can supply this
> additional load
> > > without exceeding its rating, making it run hot, etc...
> > >
> > > On a hunch I looked at the Shadio Rack site, and yep, you mean 1
> ohm.
> > > What gives?  Maybe you mean .25 ohm in series?
> > >
> > > Bob, WB2UJD
> > >
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