PG13 • 1
Ramsey Electronics Model No. PG13
Have you ever wanted to play with a controlled substance? Now
you can! It is called plasma, and it is easily generated by this
nifty high voltage kit. This is the same though more powerful
supply that is used in Plasma Balls and neon art, and can be
used for all sorts of high voltage experiments! Turn a standard
light bulb into a plasma sphere!
•
Perfect for driving a Jacob’s ladder. See plasma at work!
•
Can light many feet of neon tubing
•
Perfect for driving plasma balls, even make a standard light bulb
into a plasma sphere!
•
Optional 12VAC transformer and this kit are all you need to begin
experimenting!
•
Can generate sparks up to 2 inches.
•
Very thorough manual on high voltage safety, many neat
experiments, and lessons learned along the way.
•
Can produce many of the same effects as Tesla Coil, on a smaller
scale.
•
Great for science fairs!
DANGER
HIGH VOLTAGE
See instruction manual before operation
PG13 • 2
RAMSEY TRANSMITTER KITS
• FM100B Professional FM Stereo Transmitter
• FM25B Synthesized Stereo Transmitter
• AM1, AM25 AM Transmitters
• TV6 Television Transmitter
RAMSEY RECEIVER KITS
• FR1 FM Broadcast Receiver
• AR1 Aircraft Band Receiver
• SR2 Shortwave Receiver
• AA7 Active Antenna
• SC1 Shortwave Converter
RAMSEY HOBBY KITS
• SG7 Personal Speed Radar
• SS70A Speech Scrambler
• SP1 Speakerphone
• WCT20 Wiza rd Cable Tracer
• ECG1 Heart Monitor
• LABC1 Lead Acid Battery Charger
• IG7 Ion Generator
• CT255 Compu Temp Digital Binary Thermometer
• LC1 Inductance-Capacitance Meter
RAMSEY AMATEUR RADIO KITS
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• CW7 CW Keyer
• CPO3 Code Practice Oscillator
• QRP Power Amplifiers
RAMSEY MINI-KITS
Many other kits are available for hobby, school, Scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.
PG13 PLASMA G EN ER A TO R KIT MANUAL
Ramsey Electronics publication No. MPG13 Revision 1.1d
First printing: November 2001 MRW
COPYRIGHT 2001 by Ramsey Electronics, Inc. 590 Fishers Station Drive, V ic t or, New York
14564. All rights reserved. No portion of this publication may be copied or duplic ated without the
written permission of Ramsey Electronics , I nc. P rinted i n the United Stat es of America.
PG13 • 3
PG13 PLASMA
GENERATOR KIT
Ramsey Publication No. MPG13
Price $10.00
TABLE OF CONTENTS
Safety Guidelines .................................4
History ...................................................9
Circuit Operation .................................12
Learn As You Build .............................16
Parts List .............................................18
Assembly .............................................19
Schematic ............................................24
Power Supply ......................................25
Testing .................................................28
Troubleshooting ..................................31
Experiments ........................................32
Component Placem ent ........................42
Warranty ..............................................43
KIT ASSEMBLY
AND INSTRUCTION MANUAL FOR
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
PG13 • 4
SAFETY GUIDELINES FOR HIGH VOLTAGE AND/OR LINE POWERED
EQUIPMENT
Author: Samuel M. Goldwasser
Corrections/suggestions: sam@stdavids.picker.com
Copyright (c) 1994, 1995, 1996, 1997, 1998
All Rights Reserved
Reproduction of this document in whole or in part is permitted if both of the
following conditions are satisfied:
1. This notice is includ ed in its ent iret y at the begin ning.
2. There is no charge except to cover the costs of copying.
Introduction
Consumer electronics equipment like TVs, computer monitors, microwave
ovens, and electronic flash units, use voltages at power levels that are
potentially lethal. Normally, these are safely enclosed to prevent accidental
contact. However, during servicing, the cabinet will likely be open and safety
interlocks may be defeated. Depending on overall conditions and your general
state of health, there is a wide variation of voltage, current, and total energy
levels that can kill.
Microwave ovens in particular are probably THE most dangerous household
appliance to service. There is high voltage - up to 5,000 V or more - at high
current - more than an amp may be available momentarily. This is an instantly
lethal combination.
TVs and monitors may have up to 35 KV on the CRT but the current is low—a
couple of milliamps. However, the CRT capacitance can hold a painful charge
for a long time. In addition, portions of the circuitry of TVs and monitors - as
well as all other devices that plug into the wall socket - are line connected. This
is actually more dangerous than the high voltage due to the greater current
available - and a few hundred volts can make you just as dead as 35 KV!
Electronic flash units and strobelights have large energy storage capacitors
which alone can deliver a lethal charge - long after the power has been
removed. This applies to some extent even to those little disposable pocket
cameras with flash!
Even some portions of apparently harmless devices like VCRs and CD
players or vacuum cleaners and toasters - can be hazardous (though the live
parts may be insulated or protected - but don't count on it!
This information also applies when working on other high voltage or line
PG13 • 5
connected devices like Tesla Coils, Jacobs Ladders, plasma spheres,
gigawatt lasers, fusion generators, and other popular hobby type projects.
In addition read the relevant sections of the document for your particular
equipment. Specific safety considerations have been included where
appropriate.
Safety guidelines
These guidelines are to protect you from potentially deadly electrical shock
hazards as well as the equipment from accidental damage.
Note that the danger to you is not only in your body providing a conducting
path, particularly through your heart. An y involuntary muscle contractions
caused by a shock, while perhaps harmless in themselves, may cause
collateral damage - there are many sharp edges inside this type of equipment
as well as other electrically live parts you may contact accidentally.
The purpose of this set of guidelines is not to frighten you but rather to make
you aware of the appropriate precautions. Repair of TVs, monitors,
microwave ovens, and other consumer and industrial equipment can be both
rewarding and economical. Just be sure that it is also safe!
•
Don't work alone - in the event of an emergency another person's
presence may be essential.
•
Always keep one hand in your pocket when anywhere around a powered
line-connected or high vo lta ge system.
•
Wear rubber bottom shoes or sneakers.
•
Wear eye protection - large plastic lens eyeglasses or safety goggles.
•
Don't wear any jewelry or other articles that could accidentally contact
circuitry and conduct current, or get caught in moving parts.
•
Set up your work area away from possible grounds that you may
accidentally contact.
•
Know your equipment: TVs and monitors may use parts of the metal
chassis as ground return yet the chassis may be electrically live with
respect to the earth ground of the AC line. Microwave ovens use the
chassis as ground return for the high voltage. In addition, do not assume
that the chassis is a suitable ground for your test equipment!
•
If circuit boards need to be removed from their mountings, put insulating
material between the boards and anything they may short to. Hold them
in place with string or electrical tape. Prop them up with insulation sticks
plastic or wood.
•
If you need to probe, solder, or otherwise touch circuits with power off,
discharge (across) large power supply filter capacitors with a 2 W or
PG13 • 6
greater resistor of 100-500 ohms/V approximate value (e.g., for a 200 V
capacitor, use a 20K-100K ohm resistor). Monitor while discharging and/
or verify that there is no residual charge with a suitable voltmeter. In a TV
or monitor, if you are removing the high voltage connection to the CRT (to
replace the flyback transformer for example) first discharge the CRT
contact (under the insulating cup at the end of the fat red wire). Use a
1M-10M ohm 1W or greater wattage resistor on the end of an insulating
stick or the probe of a high voltage meter. Discharge to the metal frame
which is connected to the outside of the CRT.
•
For TVs and monitors in particular, there is the additional danger of CRT
implosion - take care not to bang the CRT envelope with your tools. An
implosion will scatter shards of glass at high velocity in every direction.
There is several tons of force attempting to crush the typical CRT. Always
wear eye protection.
•
Connect/disconnect any test leads with the equipment unpowered and
unplugged. Use clip leads or solder temporary wires to reach cramped
locations or difficult to access locations.
•
If you must probe live, put electrical tape over all but the last 1/16" of the
test probes to avoid the possibility of an accidental short which could
cause damage to various components. Clip the reference end of the
meter or scope to the appropriate ground return so that you need to only
probe with one hand.
•
Perform as many tests as possible with power off and the equipment
unplugged. For example, the semiconductors in the power supply section
of a TV or monitor can be tested for short circuits with an ohmmeter.
•
Use an isolation transformer if there is any chance of contacting line
connected circuits. A Variac(tm) (variable autotransformer) is not an
isolation transformer! However, the combination of a Variac and isolation
transformer maintains the safety benefits and is a very versatile device.
See the document "Repair Briefs, An Introduction", av ail ab le at this site,
for more details.
•
The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a
good idea but will not protect you from shock from many points in a line
connected TV or monitor, or the high voltage side of a microwave oven,
for example. (Note however, that, a GFCI may nuisance trip at power-on
or at other random times due to leakage paths (like your scope probe
ground) or the highly capacitive or inductive input characteristics of line
powered equipment.) A fuse or circuit breaker is too slow and insensitive
to provide any protection for you or in many cases, your equipment.
However, these devices may save your scope probe ground wire should
you accidentally connect it to a live chassis.
•
When handling static sensitive components, an anti-static wrist strap is
recommended. However, it should be constructed of high resistance
PG13 • 7
materials with a high resistance path between you and the chassis
(greater than 100K ohms). Never use metallic conductors as you would
then become an excellent path to ground for line current or risk
amputating your hand at the wrist when you accidentally contacted that
1000 A welder supply!
•
Don't attempt repair work when you are tired. Not only will you be more
careless, but your primary diagnostic tool - deductive reasoning - will not
be operating at full capacity.
•
Finally, never assume anything without checking it out for yourself! Don't
take shortcuts!
Safety tests for leakage current on repaired equipment
It is always essential to test AFTER any repairs to assure that no accessible
parts of the equipment have inadvertently been shorted to a Hot wire or live
point in the power supply. In addition to incorrect rewiring, this could result
from a faulty part, solder splash, or kinked wire insulation.
There are two sets of tests:
DC leakage: Use a multimeter on the highest ohms range to measure the
resistance between the Hot/Neutral prongs of the wall plug (shorted together
and with the power switch on where one exists) to ALL exposed metal parts of
the equipment including metallic trim, knobs, connector shells and shields,
VHF and UHF antenna connections, etc.
This resistance must not be less than 1M ohm.
AC leakage: Connect a 1.5K ohm, 10 Watt resistor in parallel with a 0.15 uF,
150 V capacitor. With your multimeter set on ACV across this combination
and the equipment powered up, touch between a known earth ground and
each exposed metal part of the equipment as above.
WARNING: Take care not to touch anything until you have confirmed that
the leakage is acceptable - you could have a shocking experience! The
potential measured for any exposed metal surface must not exceed 0.75 V.
If the equipment fails either of these tests, the fault MUST be found and
corrected before putting it back in service (even if you are doing this for your
in-laws!).
Some notes regarding the above safety information
While the PG13 falls under the high voltage category, many of the safety
recommendations do not apply due to the nature of high frequency high
PG13 • 8
voltage. This is only true if you do not modify the kit in any way. Here is the
reason why, which is very interes ting:
So here is the abridged answer to your question:
Sodium channels are responsible for the initiation and propagation of action
potentials. Action potentials are those electrical signals that carry
messages throughout the body whether they be neuronal or cardiac in nature.
Sodium channels go through a basic gating scheme. Upon membrane
depolarization, sodium channels open, or activate, then quickly inactivate
or close. Upon repolarization, sodium channels will go back to the resting
state at which time they are capable of opening again. Channels require a
certain amount of time to recover from inactivation or return to this
available resting state. This recovery from inactivation requires on the
order of 15 ms. The frequency at which action potentials fire is governed by
this recovery. So action potentials can fire about 60 times per second.
Stimulation at higher frequencies would for all intents and purposes drive
those sodium channels near the point of the stimulation into a long lived
inactivated state from which no action potentials could fire. So thus the
reason why lower frequency stimulation would be more deleterious than a 2
kHz frequency.
Larry E. Wagner II
Technical Associate II
Dept. of Anesthesiolo gy
P.O. Box 604
University of Rochester Medical Center
Simply put, your nerves are not fast enough to respond! Does this mean you
are not getting electrocuted? No, but current flow is harmless at these
frequencies. The real danger comes from RF burns, and that is what you will
become aware of the most when you touch the wrong things. Burning flesh
smells awful by the way. When you feel a “tickle” from the PG13 it is either
from a lower frequency component like 60 Hz, or the “tickle” of a nice RF burn.
Yes, they HURT!
PG13 • 9
HOW I ARRIVED AT THE PG13.
(A little history, if you please!)
Let me introduce myself. I am an engineer at Ramsey Electronics, and have
been so for over 12 years now. Who said anything about company faithfulness
being dead? Anyhow since I was in high school I have been messing around
with high voltage, becaus e it is a challe nge , a bit risky, and is simply
fascinating. I suppose the fixation on high voltage stems from an earlier
fascination with fire, but I won’t get into that. The connection is that fire and a
good spark are both made of the same stuff: Plasma.
This kit is NOT a Tesla Coil by any means, in fact it exhibits very little of the
effects that Tesla Coils use to achieve a very high output voltage. Tesla coils
use a completely different effect from turns ratios to achieve a high voltage
output, which involves transmission line theory, magnetic fields, and a lot of
power. Tesla coil’s output voltages are dependant upon factors such at
secondary Q factors, and not as much on turns ratios. My PG13 is completely
dependant upon turns ratios because the Q factor is too low to exhibit Tesla
effects.
This project was conceived due to an inability to find those old flyback
transformers that do not contain diodes. Diodes convert the output of a
television flyback transformer to DC, preventing them from working for many
AC experiments. I searched long and hard, and finally found a manufacturer of
a perfect experimenter’s coil. No more stopping at the side of the road at an old
console TV to see if the flyback is usable!
So, what the heck is plasma, you may ask? No, it’s not the plasma in your
blood, swimming along with the red blood cells. Plasma is matter in an
extremely excited state. Basically it is molecules being repeatedly stripped of
their electrons, and then electrons falling back into place. The process of
electrons falling into place is what gives sparks and fire (plasma) its
characteristic colors. These colors are dependant upon the mixture of gases
that the plasma is made up of, and how excited the gases are. Our atmosphere
is mostly Nitrogen, with Oxygen and other gases thrown in as an afterthought.
Nitrogen emits blues and violets mostly in a low excitement state, and that is
why sparks appear violet at low currents, and blue as the current increases.
Why is fire orange and yellow? Because particles such as carbon and ash in
the plasma are heated to incandescence, like the filament of a light bulb. If not
for the particles the flames would be blue, like Natural Gas burning.
Aurora Borealis is another example of plasma In this case upper atmosphere
molecules are excited by high energy particles from the sun. Auroras vary from
green to red, depending on intensity and elevation in the atmosphere. At higher
elevations and low atmospheric pressures found in the upper atmosphere,
Nitrogen will emit quite a bit of green. Down a few dozen kilometers closer to
earth, Oxygen ionizes (turns to plasma) much more easily and Oxygen tends to
emit red. That is why you see different colors in aurora.
PG13 • 10
To see an aurora closely, we can use Plasma balls. Plasma balls operate by
applying a high AC voltage to an electrode in the center of a glass sphere. This
high voltage must be high frequency AC in order for any current to get through
the glass of the globe and surrounding air by capacitive coupling to your hand
or the air. The current actually doesn’t go through the glass, but is induced on
either side. Typical voltages are around a few thousand volts for most
commercial plasma globes, sometimes around 10,000 volts for some
homebrew ones. Typical frequencies are from a few kilohertz to a few tens of
kilohertz.
Plasma balls will usually employ unusual gases such as helium, neon, xenon,
krypton, and argon to achieve different colors and spark types. Since gases
usually ionize more easily at low air pressures, a plasma ball’s air is first sucked
out with a vacuum pump, and then replaced with a mixture of the above gases
at about 1/10 to 1/20 of an atmosphere. These gases are noble gases, also
meaning inert, which means that they don’t readily react with other molecules
and create dangerous results. There have been reports of Plasma balls working
at atmospheric pressure, and we may try that experiment here.
I used a small water-controlled vacuum pump at home when I was a kid and a
large, green wine bottle. The best I ever got was 4” streamers at the very
bottom, which were white due to the quantity of water vapor coming back
through my hose. When your budget is $20 a month, you simply can’t afford a
vacuum pump.
Now that I have a job, I can get all of those toys I always wanted as a kid (if
my wife lets me!), but now I needed to make a new supply. My old one looked
like a rat’s nest of wires, and the television flyback wouldn’t fit in any plastic
case that I could find. It was time to make a new one that looked nice, and
didn’t periodically shock me. I decided to use my resources here at work to
make a new kit as well as a new toy for me. (The wife won’t stop me if the boss
is paying!)
Happy experimenting, and I hope you enjoy playing with high voltage as much
as I do! Oh, here is a little reference I pulled from the Internet on gases and the
colors they make. Pretty neat!
Colors and Effects of Various Gases (by Don Klipstein)
Helium - In spectrum tubes it glows a brilliant whitish yellow-orange color,
somewhat like that of a high pressure sodium lamp. I have heard that this
sometimes varies with pressure, current, and container dimensions.
Neon - Usually produces dim red blurry streamers with brighter orange "pads"
at the ends. If neon is mixed with another gas (other than helium), the streamer
color and character is often dominated by the other gas, but the ends of the
streamer are orange or pink "pads".
PG13 • 11
Carbon Dioxide - Glows a whitish or blue-white color. It is probably good to
have no direct contact with metal electrodes for long life with gases that are not
completely inert. Carbon dioxide probably requires more voltage than the noble
gases. Generally, gases and vapors with monoatomic molecules work with less
voltage than others.
Nitrogen - Streamers are usually a whitish or grayish pink or light orange. The
color may be more gray or lavender at very low currents. The apparent color
varies with what kind of lighting it is in contrast with. Requires somewhat higher
voltage than noble gases .
Air, Oxygen, Water Vapor - These require more voltage than the noble gases
and do not glow brightly. I do not recommend these. If you must use any of
these, you may also want no direct contact of gas or vapor to metal in order to
avoid corrosion problems.
Argon - Streamers are violet-lavender. The ends are blue-violet-lavender.
Argon and neon. A mixture of around 99.5 percent neon, .5 percent argon has
the lowest voltage requirement, but may not look as good as other gases.
Argon-Nitrogen mixture (as found in many light bulbs) - Streamers are whitish
or grayish pink or orange, but more lavender at low currents. The ends are
blue-violet-lavender. Requires a bit more voltage than pure argon.
Krypton - Generally lightning-like and close to white or light gray, sometimes
purplish or pinkish, depending on background lighting. Sometimes fuzzier and/
or gray-greenish, especially if the pressure and/or peak current are low.
Xenon - Usually lightning-like and bluish white or bluish gray. May get fuzzier
and more gray or lavenderish gray at lower pressure and lower peak current.
Peak currents over a few milliamps favor a more lightning-like appearance even
if the RMS current is less than a milliamp.
Don Klipstein's web site with plenty of great information on HV and plasma:
http://www.misty.com/people/don/index.html
PG13 • 12
CIRCUIT OPERATION
What is going on with this board may look simple at first, but it is actually
quite a difficult design to get working properly and reliably. A lot has to be
considered with magnet ic s when deali ng wit h high vo lt age, hi gh freque ncy
transformers. Unlike power transformers like the one powering the entire kit,
high voltage transformers have a “sweet spot”, or a resonant frequency where
they operate the most efficiently. The goal of the design is to get it working
above human hearing, otherwise the screech of high frequency from a plasma
discharge is deafening. When choosing the transformer for this design, I
wanted the best of everything: High Voltage output, High Current, High
Resonant Frequency, and the ability to generate this from a relatively low
voltage.
The transformer company we found delivered four different transformers to
us to experiment with, and a bunch of plastic spacers of varying widths. The
four transformers had increasing numbers of secondary windings, but all other
factors similar. The problem is that the more windings there are on the
secondary, the more inductance there is, meaning the resonant frequency
would be lower. The largest transformer which had 6500 turns in the
secondary would have been perfect to get 12 volts up to 25kV using a low
number of turns on the primary, but the resonance was around 13kHz. The
sound this emits is intolerable for any length of time. The coil also had the
problem of having very thin wire resulting in a low current output. They have to
use fine wire to make it fit in the transformer’s plastic case.
The smallest coil had 2000 turns on the secondary, which isn’t quite enough
to get 25kV from 12V, even in a push-pull configuration. The problem here is
we really need more than one turn of wire on the primary to make an effective
output. An advantage would be that the transformer oscillated around 35kHz,
well above hearing, but almost too high for some effects we would like to
make.
The transformer we wound up using was the third size, which has 4000
windings on the secondary, which gives us plenty of high voltage output. It
also has the larger sized wire, and with the proper spacers would oscillate
right around 18kHz. This frequency is above most people’s hearing, but your
dog won’t like this too much.
So what do those spacers do? Without getting into magnetics too much, they
lower the saturation point of the ferric core. This means the core saturates
faster with a larger gap, which also translates to a higher operating frequency.
This also means, however, that since the core saturates faster, less energy
will be transferred from the primary to the secondary, which reduces power
output.
PG13 • 13
We have included two 0.25mm spacers for you to do experiments with.
Since the transformer is specific about its “sweet spot”, we couldn’t run the
drive circuit directly from a pulse width modulator circuit (PWM). We may have
been able to tune it up really close while there was no load applied, but as
soon as we would draw a spark, the frequency would change, and our output
would drop considerably. For example if the “sweet spot” was 20kHz, and we
were driving the circuit with 20kHz, we may have 20kV on the output. Then, if
we add a new load on the output that changes the “sweet spot” to 19kHz, but
we are still driving it with 20kHz, the output may drop to only a few kilovolts.
Because of this we decided to make the transformer self-resonating. This
means as the load changes, so will the frequency, so that the transformer is
always running in the sweet spot.
The way this oscillator works is by alternately saturating the core, first in one
direction, then the other. R1 and R5 are used as a “kick start” for the oscillator.
These resistors provide some current to turn the transistors on. Because no
two transistors are perfectly alike, one will turn on before the other, providing
an imbalance.
In Figure 1, The transistor that is turned on stays on, forcing the other
transistor to turn off by directing current through the feedback winding of the
transformer in the direction required to turn the other transistor off, and turn
itself on even harder. For this illustration we’ll say that Q3 is turned on while
Q4 is turned off. As this is occurring, magnetic flux in the core is building along
with the current being drawn through Q3, because of the side of the winding
Q3 is attached to. This current is drawn through the center tap of the primary
winding through the winding, and finally down through Q3 to ground. This
rising magnetic flux in turn is inducing voltage and current in the high voltage
secondary, as well as the feedback winding. This current in the feedback
winding pushes the transistor on even harder up to the point that the core of
the transformer saturates.
Fig 1. Fig 2.
Direction of Flux
+V High Voltage
-V High Voltage
+12V
Direction of Flux
-V High Voltage
+V High Voltage
+12V
PG13 • 14
Once saturation occurs, the flux stops increasing in the core, and the current
that was induced in the feedback winding abruptly halts and reverses direction
due to a “ringing” effect. This reversal in current direction then turns off Q3
and begins to turn on Q4, which quickly ramps up the flux in the core now
heading in the other direction. (Fig 2).
This cycle goes back and forth continuously until power is removed.
To control the output voltage we can simply adjust our driving voltage.
Here’s why I chose a 12.6VAC transformer instead of a 16VAC transformer to
be used with your PG13.
One quirk we have come across is that our high voltage design cannot
produce a high current arc directly to ground. For this to actually occur we
would need a lot more parts in the circuit, and also it would reduce the safety
considerably. We decided to go for safety and stick with a lower power design.
Besides, you can pull some pretty hot arcs onto a screwdriver and other
objects, no ground needed!
To find out what we have for output voltage is a simple matter of turns ratios.
See the chart below to see the transformer secondary windings that were in
the different models of transformers that I sampled.
Winding Turns
Wire Diam.
CHT-0126A: 2000 0.1mm
CHT-0126B: 2500 0.1mm
CHT-0126C: 4000 0.1mm
CHT-0126D: 6500 0.06mm
Since we chose the C version of the transformer, we see that we have 4000
windings in the secondary. Now we need to know what is in the primary. Since
we were trying to achieve highest poss ible vo lt age out put alo ng with a dec ent
current output, I compromised at 9 turns center tapped on the primary. Since
we are in a push-pull configuration, this essentially doubles our supply voltage
across the primary. So let’s say we have a 12.6 VAC transformer supplying
our kit, and we need to know what our output voltage will be. First we have to
find what the supply voltage will become after converting the 12.6VAC which
is an RMS value to the DC value after rectification. First we convert to peak to
peak:
12.6VAC * SQRT(2) = 17.81 Vpk/pk
Then we subtract 1.4 volts for the diode drops in the bridge rectifier.
17.81—1.4 = 16.41 VDC
Now realize that the 12.6VAC rating is at the current rating of the
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