Westinghouse H-104 power supply
Unrevealed Source wrote:
"Carter-k8vt" wrote in message
t...
The 268 volts you are seeing on each plate is 268 volts -AC- to
ground; to put it another way, you are looking at a transformer
with a 268-0-268 volt secondary (or a transformer with a 536 volt
*center-tapped* secondary).
I've got that part - thanks for confirming.
Let me toss you a minor curve ball: If you were repairing this radio in
its era, you would indeed be looking for a replacement transformer with
approximately a 270-0-270 high voltage secondary winding; this is
because it was designed for 110 volts AC coming out of the socket on
your wall. Today, that voltage is 115 to 120 volts or even a bit higher
and using -today's- line voltage with a 270-0-270 winding would give you
a bit more than the 265 volts DC B+ that you are looking for. So, what I
am saying is that you could (should?) look for a transformer with a
220-0-220 or 250-0-250 high voltage winding; i.e. less (than 270-0-270)
is better.
The 265 volts you refer to is +265 volts -DC-, measured from the
filament (cathode) to ground. The voltage -across- the 5U4 filament
is 5 volts AC, the filament voltage of a 5U4.
So I need to apply 5V AC across the filament (pins 2 and 8). That's
consistent with what my understanding would have been.
Yes. That is why your replacement transformer needs a 5 volt secondary
winding (with enough current for a 5U4 filament).
And the 265V is generated by the tube, correct?
Yes, the tube changes (or 'rectifies') the 268 volts AC to 265 volts DC.
This would be a pulsed DC, would it not, coming directly off the
tube?
Yes.
In circuit, it is constant DC due to the filter capacitors?
Yes (and also due to a filter choke if one is present (rest of the
schematic is cut off).
Do I understand this correctly?
Yes.
By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.
Yes, relative to almost all of you, I am indeed a relative beginner.
And this is my first experience with a transformer/rectifier-based
radio, so I apologize if my questions are somewhat stupid.
Jeff
Nope, not stupid. Again, we were ALL beginners at one time. Asking
questions is how you learn...
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