Power Supply Help!

[Lost'n Found]

Hello.

Pardon me for this beginner question, but I have to make one thing clear.

I bought a power supply which has ratings as follows:
Secondary Output: 420 V DC @ 240 mA FWCT, 330-0- 330v, 53v Bias

I understand the first part. What does 330-0-330 v mean?
and what does 53 bias mean? The secondary part has 4 wires. I assume that
one of them gives 53v, but would be DC? Again, what is the 330-0-330v ?

Thank you very much

 

[default]

On Wed, 21 Jun 2006 22:20:38 -0400, "Lost'n Found"
<omakke1@comcast.net> wrote:

Hello.

Pardon me for this beginner question, but I have to make one thing clear.

I bought a power supply which has ratings as follows:
Secondary Output: 420 V DC @ 240 mA FWCT, 330-0- 330v, 53v Bias

I understand the first part. What does 330-0-330 v mean?
and what does 53 bias mean? The secondary part has 4 wires. I assume that
one of them gives 53v, but would be DC? Again, what is the 330-0-330v ?

Thank you very much

You are saying "power supply" but seem to be describing a transformer

label.

And from the sounds of it, you seem to have a tube type transformer.
330-0-330 is one way of saying 660 AC with a center tap - frequently
used with toob type rectifiers to provide a nominal 450 volts DC after
running through a rectifier and filter. Maybe that's where the 420
volts DC at 240 milliamps comes in (either the output of the power
supply or anticipated output in DC from the transformer after
rectification and filtering)

The 53 bias is probably a bias winding also used with toob type
equipment . If it is indeed a "power supply" the 53 bias will be a
low current 53 volt DC output.

Transformers don't output DC that takes a few more parts - describe
the "power supply" (transformers are mounted to a chassis in a power
supply)

The 4 wires is a little thin for a center tap you need three wires.
And for a bias winding another two - at least that's been the case in
every transformer I've seen. Then too if it is a "power supply" four
wires is all you need for the plate supply (the 420 volts) and bias.

Did I confuse you?


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[Lost'n Found]

Thanks for the reply.

It is actually a transformer, P-TF22814 used in Fender amplifiers.
I have 6 wires on the output side.
Two of them give 6.5V at 3.5 amp, I guess these are used for the heaters in
the tubes.

So if it it 660v AC, or 330-0-330, Can't I use solid state instead of tube
rectifiers to get 'around' 330v and a ground, forgetting about the
other -330v? would that suggest that I am getting half the power otu?

Or do these transformers do the rectifiying for me?

Now I am also assuming that the 53V Bias comes out AC.


"default" <none@nobody.net> wrote in message
news:rask92hasfrqull7cikrjflp1dts09qs1m@4ax.com...

On Wed, 21 Jun 2006 22:20:38 -0400, "Lost'n Found"
omakke1@comcast.net> wrote:

Hello.

Pardon me for this beginner question, but I have to make one thing clear.

I bought a power supply which has ratings as follows:
Secondary Output: 420 V DC @ 240 mA FWCT, 330-0- 330v, 53v Bias

I understand the first part. What does 330-0-330 v mean?
and what does 53 bias mean? The secondary part has 4 wires. I assume that
one of them gives 53v, but would be DC? Again, what is the 330-0-330v ?

Thank you very much

You are saying "power supply" but seem to be describing a transformer
label.

And from the sounds of it, you seem to have a tube type transformer.
330-0-330 is one way of saying 660 AC with a center tap - frequently
used with toob type rectifiers to provide a nominal 450 volts DC after
running through a rectifier and filter. Maybe that's where the 420
volts DC at 240 milliamps comes in (either the output of the power
supply or anticipated output in DC from the transformer after
rectification and filtering)

The 53 bias is probably a bias winding also used with toob type
equipment . If it is indeed a "power supply" the 53 bias will be a
low current 53 volt DC output.

Transformers don't output DC that takes a few more parts - describe
the "power supply" (transformers are mounted to a chassis in a power
supply)

The 4 wires is a little thin for a center tap you need three wires.
And for a bias winding another two - at least that's been the case in
every transformer I've seen. Then too if it is a "power supply" four
wires is all you need for the plate supply (the 420 volts) and bias.

Did I confuse you?


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[default]

On Thu, 22 Jun 2006 12:17:00 -0400, "Lost'n Found"
<omakke1@comcast.net> wrote:

It is actually a transformer, P-TF22814 used in Fender amplifiers.
I have 6 wires on the output side.
Two of them give 6.5V at 3.5 amp, I guess these are used for the heaters in
the tubes.

Now it is making more sense (to me)

So if it it 660v AC, or 330-0-330, Can't I use solid state instead of tube
rectifiers to get 'around' 330v and a ground, forgetting about the
other -330v? would that suggest that I am getting half the power otu?

Sure you can use a pair of diodes like 1N4007 rated at something like
1,000 volts at one amp (and only cost about 20 cents) The diodes
convert it into DC.

Connect the center tap to ground and each diode's anode to one of the
330 wires and both diode's cathodes together and that becomes the
positive supply. When you add filter capacitors to take the
hum/ripple out you will get about 466 volts of (unloaded) DC output
(so use some 500 Volt rated capacitors)

You are converting from RMS to peak. RMS is the equivalent voltage of
the sine wave - the actual wave is continuously varying to achieve a
330 volt rating (the way transformers are rated and labeled)

You want to use a pair of diodes not just one side of the transformer
- the ripple is less because it is full wave rectification instead of
half wave. And you get the full power of the transformer and even if
you don't need it, you will stress the secondary windings less.

Or do these transformers do the rectifiying for me?

Transformers do no rectification whatsoever (even those "wall wart"
thingees that power junk today have diodes in them to convert the AC
to DC). They may call them DC transformers but their ain't no such
animal - strictly speaking.

Now I am also assuming that the 53V Bias comes out AC.

Yes, if it is a transformer it will be AC

To convert from RMS to peak you multiply by 1.414
To convert peak to RMS you multiply by .707 (the reciprocal)

The 240 ma rating is RMS also, the actual DC current you can pull out
after it is rectified and filtered is less than 170 milliamperes

Should be good for about 70 watts of power.

The original design may have called for filter chokes to keep the
ripple down (back in the old days, they frequently used chokes as well
as capacitors to eliminate hum) filter chokes drop a little more
voltage than large capacitor filters - today caps are cheaper, chokes
expensive.

The original may have also used toob type rectifiers - they waste a
little voltage and power too. Most common toob type rectifier in that
power class was the 5U4 - a tube with 5 volt filament (heater)

What is your application? Building and amp or repairing one? Does
the schematic call for the bias supply? (not all amps use a separate
bias supply)

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[Lost'n Found]

Thanks for the help, it makes lots of sense. It is just that I never dealt
with transformers in real life, and I am not used to the standard
convention.

I am designing a hybrid amplifier, , tubes and solid state. Mainly the tubes
will be used to give the distortion, but they can be bypassed in case the
amp is needed to be used for some other instruments.

It just came to my mind that this high voltage may be too much for the
12AX7's, they seem to be rated at 300v.

I'll see. . . Some experimentation wouldn't hurt.

"default" <none@nobody.net> wrote in message
news:0pjl92588bj86fg0r2vmrlfdcfoef5a3h5@4ax.com...

On Thu, 22 Jun 2006 12:17:00 -0400, "Lost'n Found"
omakke1@comcast.net> wrote:

It is actually a transformer, P-TF22814 used in Fender amplifiers.
I have 6 wires on the output side.
Two of them give 6.5V at 3.5 amp, I guess these are used for the heaters
in
the tubes.

Now it is making more sense (to me)

So if it it 660v AC, or 330-0-330, Can't I use solid state instead of tube
rectifiers to get 'around' 330v and a ground, forgetting about the
other -330v? would that suggest that I am getting half the power otu?

Sure you can use a pair of diodes like 1N4007 rated at something like
1,000 volts at one amp (and only cost about 20 cents) The diodes
convert it into DC.

Connect the center tap to ground and each diode's anode to one of the
330 wires and both diode's cathodes together and that becomes the
positive supply. When you add filter capacitors to take the
hum/ripple out you will get about 466 volts of (unloaded) DC output
(so use some 500 Volt rated capacitors)

You are converting from RMS to peak. RMS is the equivalent voltage of
the sine wave - the actual wave is continuously varying to achieve a
330 volt rating (the way transformers are rated and labeled)

You want to use a pair of diodes not just one side of the transformer
- the ripple is less because it is full wave rectification instead of
half wave. And you get the full power of the transformer and even if
you don't need it, you will stress the secondary windings less.

Or do these transformers do the rectifiying for me?

Transformers do no rectification whatsoever (even those "wall wart"
thingees that power junk today have diodes in them to convert the AC
to DC). They may call them DC transformers but their ain't no such
animal - strictly speaking.

Now I am also assuming that the 53V Bias comes out AC.

Yes, if it is a transformer it will be AC

To convert from RMS to peak you multiply by 1.414
To convert peak to RMS you multiply by .707 (the reciprocal)

The 240 ma rating is RMS also, the actual DC current you can pull out
after it is rectified and filtered is less than 170 milliamperes

Should be good for about 70 watts of power.

The original design may have called for filter chokes to keep the
ripple down (back in the old days, they frequently used chokes as well
as capacitors to eliminate hum) filter chokes drop a little more
voltage than large capacitor filters - today caps are cheaper, chokes
expensive.

The original may have also used toob type rectifiers - they waste a
little voltage and power too. Most common toob type rectifier in that
power class was the 5U4 - a tube with 5 volt filament (heater)

What is your application? Building and amp or repairing one? Does
the schematic call for the bias supply? (not all amps use a separate
bias supply)

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[default]

On Fri, 23 Jun 2006 00:11:10 -0400, "Lost'n Found"
<omakke1@comcast.net> wrote:

I am designing a hybrid amplifier, , tubes and solid state. Mainly the tubes
will be used to give the distortion, but they can be bypassed in case the
amp is needed to be used for some other instruments.

Sounds like your intent is to get the "grudge" sound from the toobs

and only when needed.

I don't know how much of the coloration you want may be caused by the
over driven output tubes in combination with the transformer . . . but
you're experimenting . Surely there's enough interest in just what
you intend that its probably already been done or tried.

It just came to my mind that this high voltage may be too much for the
12AX7's, they seem to be rated at 300v.

Yeah, that do seem like a lot for a preamp toob. Most amps use simple
resistor dividers to limit the voltage down to the driver and phase
inverting stages. Lots of schematics on the net.

I'll see. . . Some experimentation wouldn't hurt.

I was working at a small power supply manufacturer some years ago, and
we had a client who was more or less interested in doing the same
thing. A tube or two for sound coloration and transistors to drive
the speakers. He was unsuccessful, but I have no real idea how
competent he was. (he was probably more enthusiastic than competent)

We wound a few power supply transformers for him and he was impressed
with the efficiency and quality, and wanted us to make audio output
transformers. My boss wouldn't go for it Plan "B" for the client
was to just make good tube type instrument amplifiers, and relegate
the semiconductors to preamp, bias, and power supply uses.

I did dissect one of the output transformers that he brought in to
reverse engineer it. It would have been relatively more difficult to
make than ordinary power transformers, but doable and I wished we had
made them. "There was no money in it," (lot of design effort with no
quantity in sales) but a lot of what we did, we took on only because
other's had given up, and it was good PR for that reason.

His sample transformer had windings for both the cathode and plate, I
think it was called an"ultralinear" transformer.

It is probably foolish to use a 70-100 watt plate transformer for a
few low power tubes. You could just as easily do something like take
a pair of 12 volt transformers and use one to step down to 12 and run
the filaments and another to work stepping up the 12 back to 120 just
for the power line isolation that provides - the RMS to peak would
give you a reasonable plate supply voltage for preamp tubes.

Sounds like an interesting project.
--

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