sb101,102,hw101.

[Ron Bracklow]

I aggree! I think there are too many people making issues over the voltage
issue that is of no concern. These radios have built in voltage regulation
tubes which handle any voltage variations!!

Ron, N6PWW

-----Original Message-----
From: Heathkit Owners and Collectors List
[mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Keith Rowland
Sent: Thursday, February 06, 2003 4:59 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: sb101,102,hw101.


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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