Help on HT-32A transformer

[Antonio Vernucci]

I friend of mine has to rewind the transformer of his Hallicrafters HT-32A, but
he does not know the precise AC voltages (apart from filaments of course).

AC voltages could be determined knowing the DC output voltages, but it would be
safer to take measured data.

I wonder whether anyone has, by any chance, noted down the AC voltages?

Thanks and 73

Tony I0JX
Rome, Italy

[coffelt2]

"Antonio Vernucci" <vern...@tin.it> wrote in message
news:4af4abf7$0$1110$4faf...@reader1.news.tin.it...

I've only been up against the wall twice, and I unwound the burned windings,
and counted the turns. (write the numbers down, and don't lose the paper)-
--------- (don't ask me how I know)

Old Chief Lynn, W7LTQ didadidadit

[Antonio Vernucci]

> I've only been up against the wall twice, and I unwound the burned windings,
> and counted the turns. (write the numbers down, and don't lose the paper)-
> --------- (don't ask me how I know)
>

Thanks for the tip, but in our case the transformer had already been re-wound
once. Unfortunately voltages are incorrect, so it must be re-wound for the
second time. And it is therefore not possible to determine the number of turns
for the various windings.

73

Tony I0JX

[Roger D Johnson]

Hi Tony...

Try here:

http://www.harbachelectronics.com/main/page_xfmr_catalogs.html

73, Roger

--
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/

Remove tilde (~) in address to answer.

[Scott Dorsey]

How incorrect ARE the voltages?

If the plate voltage is 20% high for instance, measuring the DC level,
that means the AC voltage on that winding is 20% high too. And so you
need to remove 20% of the windings. So you do have a reference after all.

In the solid state world you can just assume the DC voltage after the
rectifier is 1.414 times the AC voltage, minus the diode drop. Problem
is that in the tube world there is often a substantial resistive loss
through the vacuum diode.

But, you can measure that! Measure the DC drop across the diode, then
work from the desired DC voltage, plus the drop, times 1.414 to get
the AC you need. (This is assuming the diode drop will change only a
little bit once you get the voltage perfect. If it's not, use the
nomograph in the RCA HB-3 handbook to work it out).
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Antonio Vernucci]

> Hi Tony...
>
> Try here:
>
> http://www.harbachelectronics.com/main/page_xfmr_catalogs.html
>
> 73, Roger

Thanks, VERY useful. They give all the data I need!

Not common to get such an appropriate answer!

73

Tony I0JX

[Antonio Vernucci]

> How incorrect ARE the voltages?
>
> If the plate voltage is 20% high for instance, measuring the DC level,
> that means the AC voltage on that winding is 20% high too. And so you
> need to remove 20% of the windings. So you do have a reference after all.
>
> In the solid state world you can just assume the DC voltage after the
> rectifier is 1.414 times the AC voltage, minus the diode drop. Problem
> is that in the tube world there is often a substantial resistive loss
> through the vacuum diode.
>
> But, you can measure that! Measure the DC drop across the diode, then
> work from the desired DC voltage, plus the drop, times 1.414 to get
> the AC you need. (This is assuming the diode drop will change only a
> little bit once you get the voltage perfect. If it's not, use the
> nomograph in the RCA HB-3 handbook to work it out).
> --scott

Hello Scott,

yes, the difference between the voltages measured on the (ill) re-wound
transformer and the original AC voltages (that I now precisely know) can be
useful to determine how many turns more or less are required for each winding.

That can be a useful information, as a potential problem is the fact that the
original transformer was designed for 60 Hz, and the turns, once calculated for
50 Hz operation on the same iron, may not fit the available space.

Anyway I should get that transformer within a few days, and I will then discuss
with the rewinder how to best proceed.

73

Tony I0JX