Query: 400Hz Xformers
 

I have a poser for the group: I just obtained a fairly rare PP-32AR AC
power supply for the Hallicrafters ARR-5 and ARR-7 receivers. As an
airborne unit, its designed for 115VAC, 400-1000 HZ operation. I have
worked with modern 400Hz power supplies and appreciate the nuances of
same. I also have and use some rather "broadband" power transformers
that will run from 50 to 1000Hz power. The PP-32 was designed and
fielded in 1943 and would have employed technology of the era,
obviously. The transformer in this supply, given ratings, is arguably
the same size one would expect for a 60Hz unit; its fairly massive,
especially when compared to the compact units you'd expect in a modern
airborne supply. My question is, then, does anyone agree and suggest
that this unit might well work on 60Hz AC? As an aside, when I popped
the cover off, I noticed a chunk of ac lamp-cord soldered to the inside
of the Cannon input power receptacle as if some had run it (perhaps?) on
household current. Could these early 400Hz transformers have actually
originally been appropriate for 60Hz? I know (think?) that some folks
ran their APR-4 airborne receivers on 60Hz and they are of the same
generation of equipment. Finally, I note that there are no markings on
the transformer other than the pin designations. Also, there is a 80v
input tap on the primary for whatever reason; the book does not mention
it. I plan to try the 100w light bulb trick to see what might happen
but if anyone has any insights, I certainly like to hear them.
Tnx de Jeep/K3HVG

Query: 400Hz Xformers
 

In article ,
K3HVG wrote:
I have a poser for the group: I just obtained a fairly rare PP-32AR AC
power supply for the Hallicrafters ARR-5 and ARR-7 receivers. As an
airborne unit, its designed for 115VAC, 400-1000 HZ operation. I have
worked with modern 400Hz power supplies and appreciate the nuances of
same. I also have and use some rather "broadband" power transformers
that will run from 50 to 1000Hz power. The PP-32 was designed and
fielded in 1943 and would have employed technology of the era,
obviously. The transformer in this supply, given ratings, is arguably
the same size one would expect for a 60Hz unit; its fairly massive,
especially when compared to the compact units you'd expect in a modern
airborne supply. My question is, then, does anyone agree and suggest
that this unit might well work on 60Hz AC?

I would be VERY skeptical. Get it on a bridge and measure it. If you
don't have a bridge, try putting it in series with a 60W bulb, measure
the voltage across the bulb and the voltage across the transformer and
ONLY do that for a few seconds.

It is possible they might have used a transformer capable of running
on 60 Hz. It's also possible that the size is deceptive and it will
explode into flames on 60 Hz the way modern 400 Hz transfrmers do.

It will, of course, require much more supply capacitance even if the
transformer works without overheating.

As an aside, when I popped
the cover off, I noticed a chunk of ac lamp-cord soldered to the inside
of the Cannon input power receptacle as if some had run it (perhaps?) on
household current. Could these early 400Hz transformers have actually
originally been appropriate for 60Hz? I know (think?) that some folks
ran their APR-4 airborne receivers on 60Hz and they are of the same
generation of equipment.

Have the supply caps been replaced?

Finally, I note that there are no markings on
the transformer other than the pin designations. Also, there is a 80v
input tap on the primary for whatever reason; the book does not mention
it. I plan to try the 100w light bulb trick to see what might happen
but if anyone has any insights, I certainly like to hear them.

Try the lightbulb briefly, measure voltages, and see how much current
the thing is really going to pull when you plug it in, before even
thinking of plugging it in.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Query: 400Hz Xformers
 

I'd suggest using the lightbulb method, but disconnecting
all loads on the secondaries. If it starts drawing much current,
say more than 1/4-1/2 amp, you know it won't work with a load.

As someone else mentioned, you'll need to put in much bigger
filter caps if you run it a 60 Hz as well.

Good luck!

Steve

Query: 400Hz Xformers
 

Well, to all those who offered replies and info, the results of the
light-bulb test are in. At about 30v applied via Variac, the windings
began to chatter and the current was observed to be much too high. So,
its obvious now that it will not function. As mentioned, though, I have
suitable transformer that will mate the existing bolt pattern... how's
that for luck!!! Again, many tnx for the insights.
Jeep/K3HVG