[Hallicrafters] Lets hash it over one more time.

[Todd, KA1KAQ]

Oh, c'mon Gary - everyone knows those tubes work faster with higher
filament voltages! Makes more sound come outta the speaker, too.

I remember when I was off at school, taking bad tubes and putting them
into the tube tester and cranking up the filament voltage until they
exploded inside. Quite a light show! Was great fun until we let some
smoke out of one of the tube testers......ooops! Don't try this at
home, boys and girls.

More seriously though, you make a good point about the voltage
increases for the very old 110v gear and even 115v stuff, from some of
today's higher supplied voltages. Most all of my gear is rated for 115
or 120v +/- some percentage. I think the SX-28 is a 115 volt rig. I'm
also very lucky that 120 volts is considered high on my line, it hangs
right around 117 most of the time.

For those folks with line voltage much over 120 volts, do pay
attention to what Gary is saying here. I know that most of the older
gear was designed with a margin of safety, but some of the line
voltages I've heard from others (125+) would make even me nervous. I
only have a handful of 110v stuff which I'm pretty careful with. But
if I had line voltage issues here, I'd certainly take that into
account before putting power to anything.

~ Todd/'Boomer'  KA1KAQ

On 7/29/05, GBrown <gkbrown at gwi.net> wrote:
> I know the topic of power trannys and primary voltages have been hashed over
> many a times but thought I would just jump in with another perspective that
> I don't think crossed to many minds.
>     Lets start with ahhhhhhhhhhhhh, an SX-28A power tranny, or any power
> tranny that fits the approx. voltages I am about to use.
> Lets use 115 volts AC. as a starting point for primary side of transformer.
> Now, lets say there is 230 turns of wire on the primary. This will give us
> .5 VPT (volts per turn).
> This transformer will give us the following.
> .478 VPT @ 110 VAC
> .500 VPT @ 115 VAC
> .521 VPT @ 120 VAC
> .543 VPT @ 125 VAC.
>     Now, lets just say we have a secondary voltage of 600 volts. I know
> BORINGGGGGGGGGG but just hang in there.
> That's 1200 turns. OK, now lets do some math.....
> .478 VPT X 1200 turns = 573.6 volts
> .500 VPT X 1200 turns = 600.0 volts
> .521 VPT X 1200 turns = 625.2 volts
> .543 VPT X 1200 turns = 651.6 volts
> This gives us a difference of 78 volts between 110 volts and 125 volts on
> the primary. REMEMBER, turns remain the same. That's about a 12% difference
>     Now, what about filament voltages
> 12% of 6.3 volts is .756 volts. 6.3 + .756 = 7.056 volts
> 12% of 5.0 volts is .600 volts. 5.0 + .600 = 5.600 volts.
> What I am trying to get across is, do you want your filaments running almost
> another volt higher than normal?