Operating Instruction Manual
TOA PROFESSIONAL POWER AMP
Model P-150M, P-300M
TOA ELECTRIC CO, LTD.
KOBE, JAPAN
Contents
Precautions................................................ 2
General Description........................................ 2
Features................................................... 3
Specifications
...........................................
4~5
Performance Graphs ..................................... 6~9
Front Panel............................................... 10
Rear Panel................................................ 11
Input/Output Connections.............................. 12~14
Installation Precautions ................................ 15~17
25/70
Volt
Distribution
Systems
........................
18~19
Appearance ............................................... 20
— 1 —
Precautions
1. XLR type audio connectors are factory wired as follows.
Pins 1 and 2 are ground (shield); pin 3 is hot (high, plus).
The connector wiring changes with use of an optional matching transformer.
(Model No. PU-101T)
Pin 1 is ground (shield), Pin 2 is cold (low, minus), and pin 3 is hot (high,
plus).
2. Care should be taken in making connections, selecting signal sources and
controlling the output level to avoid any damage to loads.
3. Never place the two amplifier outputs parallel to each other.
4. Do not operate the amplifier from a power mains which exceeds the
indicated mains voltage by more than 10%.
5. Never connect the output of the amplifier to any other power source.
6. Do not expose the amplifier to corrosive chemicals or liquids, such as soft
drinks, salt water, etc.
7. Always refer the amplifier to qualified technical service personnel. There
are no user servicable parts inside.
General Description
The P-150M and P-300M are professional quality single channel (mono) power
amplifiers, with 8 ohm outputs and built-in output transformers for 25-volt and
70-volt lines, designed for commercial and professional sound applications.
The P-150M and P-300M deliver 150 watts and 300 watts, respectively, with 8 ohm
loads or with 25-volt or 70-volt distributed system loads.
Both feature provisions for octal socket mounting of matching transformers to
convert unbalanced inputs to balanced, magnetic circuit breakers, calibrated
input attenuators short circuit protection circuitry, 3-second turn-on delay,
current limiter protection circuitry, protection indicator LED's ground terminal
strip and high pass filter. These features combine to ensure an extremely high
level of reliability and durability.
Each amplifier is mechanically reinforced with a rugged front panel made of
3mm(l/8") thick cast-aluminum, and further strengthened by use of 3mm(l/8")
thick steel liner, thus enabling them to withstand even the roughest use.
For easy maintenance and service, the amplifiers are built with modular, plug-in
boards on a sub-chassis that can be quickly removed for repair or replacement.
— 2 —
Features
1. Magnetic Circuit Breaker Power Switch
2. Calibrated Input Attenuator
3. Short-Circuit Protection Circuitry
4. 3-Second Turn-On Delay
Both the primary mains (A.C. line) overload protection and the on/off switch
are combined into a rocker-actuated, magnetic circuit breaker whose
operation, unlike fuses, is predictable and independent of temperature.
Returning the switch to the "on" position resets the system.
A 22-step detented input attenuator is provided for easy, accurate input
sensitivity adjustment. The attenuators are in 2dB steps from 0dB
attenuation to -34dB, then in steps of -37dB, -42dB, -50dB, infinity. This
arrangement provides a smooth, noise free transition from the highest to the
lowest audio level.
Speaker protection is provided with relay circuitry that disconnects the load
whenever a short-circuit or harmful D.C. current is present across the output
terminals.
To help eliminate annoying clicks or pops which can occur upon turn-on in
large sound systems, a three second mute/delay circuit is incorporated. The
mute/delay circuit actuates the relay, and then disconnects the speaker the
instant the circuit breaker is shut off.
5. Current Limiter Circuitry
Protection against shorted and low impedance loads is provided with
dependable current limiting as well as protection against overloaded power
supplies and input overload.
6. Protection Indicator LED (Including Thermal Warning)
The LED illuminates when the protection relay is activated in the following
situations.
1) Short-circuit
2) D.C. drift
3) Turn-on delay
The LED also flashes when either of two heat sinks reaches more than 105°C
in temperature.
7. Signal Presence Indicator LED
The LED glows when a signal greater than -30dB level is fed to the inputs
regardless of the input attenuator setting and output power level. The LED is
helpful in assuring sufficient input signal is fed to drive the amplifiers.
8. Peak Indicator LED
The LED is actuated by means of an input/output comparator, and glows
when the output signal is clipped.
9. Ground Terminal Strip
Provision for isolating chassis ground from signal ground is provided on the
rear panel.
10. Heavy Aluminum Die-Cast Panel
The power amplifiers are constructed to withstand even the roughest use on
the road. Their aluminum die-cast front panels are mountable in standard
19-inch rack. A pair of sturdy carrying handles provides protection for the
front panel controls and easy handling.
11. Built-in Matching Transformer
The matching transformer is provided for a constant voltage distribution
system of 70 volts or 25 volts.
— 3 —
Specifications (P-150M)
(DIRECT OUTPUT)
Power Output
150 watts minimum sine wave continuous average power
output with 8-ohms loads over a power band from 20Hz to
20kHz. The maximum Total Harmonic Distortion (THD)
at any power level from 250 milliwatts to 150 watts shall
be not mo re t han 0.1%.
Controls
Input Attenuator
22-position, log-linear, detented and dB-calibrated input
attenuator attenuates input signal in 2dB steps from 0dB
attenuation to -34dB, th en in steps of -37dB, -42dB,
-50dB, i nfinity.
220 watts minimum sine wave continuous average power
output with 4-ohm loads over a power band from 20Hz to
20kHz. The maximum Total Harmonic Distortion (THD)
at any power level from 250 milliwatts to 220 watts shall
be not mor e than 0.15%.
160 watts continuous average sine wave power into 8
ohms with less than 0.1% THD, at 1 kHz.
Frequency Response
+0dB, -0.5dB, 20Hz to 20kHz
Total Harmonic Distortion
Less th a n 0.01% at 150 watts, 8-ohms, 1kHz
Less than 0.1% at 150 watts, 8-ohms, 20Hz to 20kHz
Intermodulation Distortion
0.05% using frequencies of 60Hz and 7kHz, mixed in a ratio
of 4:1, at power output of 50 watts into 8-ohms
Input Sensitivity
An input of +4dB (1.23V), ±0.5dB, produces an output of
150 watts into 8-ohm, INPUT ATTENUTOR set for
maximum level
Input Impedance
10k-ohms (unbalanced)
Damping Factor
Greater than 150 at any frequency from 20Hz to 1kHz
Greater than 70 at any frequency from 20Hz to 20kHz
Impedance Actual Output
Less than 0.06 ohms at any frequency from 20Hz to 1kHz
Less than 0.12 ohms at any frequency from 20Hz to 20kHz
Hum and Noise
110dB below rated output (20Hz — 20kHz)
115dB below rated output (IHF-A weighted)
Rise Time
10 microseconds, or better (10% -90% of 1 volt at 1kHz
square wave output)
Slew Rate
10 volts per microsecond, or better (at 50 watts into 8-ohm,
200kHz square wave input)
Phase Shift
20Hz to 20kHz, ±15 degrees
Offset Voltage
Less tha n ±10mV DC
Input Connectors
One "male" and one "female" XLR connector in parallel,
pin 2 "cold", pin 3 "hot", and pin 1 "shield". XLR's are
unbalanced and parallel to two tip-sleeve (standard)
phonejacks.
Circuit Breaker AC Switch
Accessory Switch (IN/OUT)
Bypass for octal socket
Overall Protection
AC line is protected by circuit breaker.
Protection LED flash when heat sink temperature reaches
more th an 105°C.
Protection LED come on when the relay is activated by the
DC current flow to output or by short circuit.
Turn On/Turn Off
No turn off transient. Three second delay turn on with
minimum thumps and no dangerous transients
AC Line Voltage
AC mains. 50Hz/60Hz
Power Consumption
400 watts maximum
Finish
Black painting
Dimensions (W×H×D)
483 × 133 × 475
19 × 5-1/4 × 18-3/4 (inches)
Weight
18kg (40 lb s)
(mm)
SPECIFICATION (TRANSFORMER OUTPUT)
Power Output
150 watts minimum sine wave continuous average power
output with either a 25-volt or 70-volt distribution system
over a power band f rom 30Hz to 15kHz.
The maximum THD at any power level 250 milliwatts to
150 watts shall be not more than 0.6%.
Output Impedance
Designed for load impedances of 4.2-ohms (25 volts) or 33ohm (70 volts).
Accessory Socket
8-pin octal socket accepts an optional matching transformer module for balanced input, or user options (pins
include ±VCC, signal input/output and circuit ground)
Output Connectors
Barrier Strip Terminal
Ground Terminal Strip
2 lug terminal block with removal shorting strap
Indicators
Green LED for signed presence
Red LED for output clipping
Red LED for circuit protection and thermal warning
Green LED for power ON.
— 4 —
Specifications (P-300M)
(DIRECT OUTPUT)
Power Output
300 watts minimum sine wave continuous average power
output with 8-ohm loads over a power band from 20Hz to
20kHz. The maximum Total Harmonic Distortion (THD)
at any power level from 250 milliwatts to 300 watts shall
be not more than 0.1%.
Controls
Input Attenuator
22-position, log-linear, detented and dB-calibrated input
attenuator attenuates input signal in 2dB steps from 0dB
attenuation to -34dB, then in steps of -37dB, -42dB,
-50dB, infinity.
480 watts minimum sine wave continuous average power
output with 4-ohm loads over a power band from 20Hz to
20kHz. The maximum Total Harmonic Distortion (THD)
at any power level from 250 milliwatts to 480 watts shall
be not mo re th a n 0.15%.
320 watts continuous average sine wave power into 8
ohms with less than 0.1% THD, at 1kHz.
Frequency Response
+0dB, -0.5dB, 20Hz to 20kHz
Total Harmonic Distortion
Less th an 0.01% at 300 watts, 8-ohms, 1kHz
Less than 0.1% at 300 watts, 8-ohms, 20Hz to 20kHz
Intermodulation Distortion
0.05% using frequencies of 60Hz and 7kHz, mixed in a ratio
of 4:1, at power output of 100 watts into 8-ohms
Input Sensitivity
An input of +4dB (1.23V), ±0.5dB, produces an output of
300 watts into 8-ohm, INPUT ATTENUATOR set for
maximum level
Input Impedance
10k-ohms (unbalanced)
Damping Factor
Gr eat er th a n 260 at any fr e q uen c y f r o m 20Hz t o 1 kHz
Greater than 95 at any frequency from 20Hz to 20kHz
Impedance Actual Output
Less than 0.03 ohms at any frequency from 20Hz to 1kHz
Less than 0.08 ohms at any frequency from 20Hz to 20kHz
Hum and Noise
109dB below rated output (20Hz — 20kHz)
114dB belo w rated output (1HF-A weighted)
Rise Time
10 microseconds, or better (10% –90% of 1 volt at 1kHz
square wave output)
Slew Rate
10 volts per microsecond, or better (at 100 watts into 8-
ohm, 200kHz square wave input)
Phase Shift
20Hz to 20kHz, ±15 degrees
Offset Voltage
Less than ±10mV DC
Input Connectors
One "male" and one "female" XLR connector in parallel,
pin 2 "cold", pin 3 "hot", and pin 1 "shield". XLR's are
unbalanced and parallel to two tip-sleeve (standard)
phonejacks.
Circuit Breaker AC Switch
Accessory Switch (IN/OUT)
Bypass for octal socket
Overall Protection
AC line is protected by circuit breaker.
Protection LED flash when heat sink temperature reaches
more th an 105°C.
Protection LED come on when the relay is activated by the
DC current flow to output or by short circuit.
Turn On/Turn Off
No turn off transient. Three second delay turn On with
minimum thumps and no dangerous transients
AC Line Voltage
AC mains. 50Hz/60Hz
Power Consumption
850 watts maximum
Finish
Black painting
Dimensions (W×H×D)
483 × 222 × 475
19 × 8-3/4 × 18-3/4 (inches)
(mm)
Weight
28kg (62 lbs)
SPECIFICATION (TRANSFORMER OUTPUT)
Power Output
300 watts minimum sine wave continuous average power
output with either a 25-volt or 70-volt distribution system
over a power band from 30 Hz to 15kHz.
The maximum THD at any power level from 250
milliwatts to 300 watts shall be no more than 0.5%.
Output Impedance
Designed for load impedances of 2.1-ohms (25 volts) or 16-
ohms (70 volts).
Accessory Socket
8-pin octal socket accepts an optional matching
transformer module for balanced input, or user options
(pins include ±VCC, signal input/output and circuit
ground)
Output Connectors
Barrier Strip Terminal
Ground Terminal Strip
2 lug terminal block with removal shorting strap
Indicators
Green LED for signal presence
Red LED for output clipping
Red LED for circuit protection and thermal warning
Green LED for power ON
— 5 —
Performance Graphs (P-150M)
P-150M DIRECT OUTPUT
POWER BANDWIDTH
T.H.D. vs FREQUENCY
POWER OUTPUT vs LOAD IMPEDANCE
T.H.D vs POWER OUTPUT
FREQUENCY RESPONSE
INTERMODULATION DISTORTION
VS POWER OUTPUT
MEASURED WITH A 4 : 1 MIX AT 60Hz and 7kHz
DAMPING FACTOR vs FREQUENCY
AT 8 LOAD IMPEDANCE
ACTUAL OUTPUT IMPEDANCE
vs FREQUENCY
— 6 —
PHASE RESPONSE
Performance Graphs (P-150M)
POWER CONSUMPTION
P-150M TRANSFORMER OUTPUT
T.H.D. vs FREQUENCY
POWER EFFICIENCY
T.H.D. vs POWER OUTPUT (at 1kHz)
FREQUENCY RESPONSE
— 7 —
Performance Graphs (P-300M)
P-300M DIRECT OUTPUT
POWER BANDWIDTH
T.H.D. vs FREQUENCY
POWER OUTPUT vs LOAD IMPEDANCE
T.H.D vs POWER OUTPUT
FREQUENCY RESPONSE
INTERMODULATION DISTORTION
VS POWER OUTPUT
MEASURED WITH A 4 : 1 MIX AT 60 Hz and 7 kHz
DAMPING FACTOR vs FREQUENCY
AT 8 LOAD IMPEDANCE
ACTUAL OUTPUT IMPEDANCE
vs FREQUENCY
— 8 —
PHASE RESPONSE
Performance Graphs (P-300M)
POWER CONSUMPTION
P-300M TRANSFORMER OUTPUT
T.H.D. vs FREQUENCY
POWER EFFICIENCY
T.H.D. vs POWER OUTPUT (at 1kHz)
FREQUENCY RESPONSE
— 9 —
Front Panel
P-150M
P-300M
Input Attenuator
Calibrated in dB, detented input attenuator decrease input signal levels before the amplifier stage.
Power Indicator LED
The green LED glows when the power switch is "on".
Signal Presence Indicator LED
The LED glows when a signal greater than -30dB is fed to the input regardless of the input attenuator
setting and output power level.
Peak Indicator LED
The LED glows when the output signal is clipped. In such a case, lower the input attenuator level.
Protection Indicator LED
This LED remains lit for 3 seconds after the power switch has been turned on. It also comes on when the
protection circuit is activated, and flashes when the temperature of the heat sink exceeds 105°C.
Circuit Breaker Power Switch
This is a combined switch of circuit breaker and a power mains ON/OFF switch. If the circuit breaker
trips, it may be reset by first setting to the "OFF" position and then returning to the "POWER ON"
position. Always check the amplifier and associated wiring before resetting the circuit breaker.
— 10 —
Rear Panel
P-150M
P-300M
Input connectors
The two XLR input connectors are unbalanced and wired parallel to each other with two phone jacks that
can accept both a tip/sleeve and a tip/ring/sleeve type of plug.
Accessory
To convert the XLR input connectors to balanced operation, remove the octal socket cover and insert the
matching transformer (PU-101T). Then loosen the screw and set the In/Out switch to "In" afte r removing
the L-shaped metal fitting. You can prevent accidental change in switch position by attaching the metal
fitting to the OUT side.
Output Connectors
Barrier strip terminals are provided for output connections of amp out (more than 4 ohms), 25-volt and 70-
volt distribution systems. When applying the amp out, remove the U-shaped jumper on the strip
terminals.
Ground Terminal Strip
Remove the strap to isolate chassis ground from signal ground. This may help prevent any ground loop
hums caused by multiple ground paths.
AC Power Cord.
— 11 —
Input/Output Connections
P-150M Typical Hookup
All XLR type connectors are unbalanced connec-
tion.
The pins 1 and 2 are ground (shield) the pin 3 hot
(high, plus).
All phone jacks are unbalanced connection.
• Low Impedance Loud Speaker Hookup
Remove U-shaped Jumper
UNBALANCED SIGNAL
FROM PREAMPLIFIER
MIXER, ETC.
• Balanced Input Connection
4~16 ohm
BALANCED SIGNAL
FROM PREAMPLIFIER,
MIXER, ETC.
25 Volt Distribution System
UNBALANCED SIGNAL
FROM PREAMPLIFIER
MIXER, ETC.
OPTIONAL INPUT TRANSFORMER
model PU-101T
— 12 —
With PU-101T
The pin 1 ground (shield)
The pin 2 cold (low, minus)
The pin 3 hot (high, plus)
The total impedance should be
more than 4.2 ohms
Input/Output Connections
P-150M Typical Hookup
70 Volt Distribution System
UNBALANCED SIGNAL
FROM PREAMPLIFIER
MIXER, ETC.
P-300M Typical Hookup
All XLR type connectors are unbalanced
connection. The pins 1 and 2 are ground
(shield) the pin 3 hot (high, plus)
All phone jacks are unbalanced connection.
Low Impedance Loud Speaker Hookup
The total impedance should be
more than 33 ohms
Remove U-shaped Jumper
4~16
ohm
UNBALANCED SIGNAL
FROM PREAMPLIFIER
MIXER, ETC.
Balanced Input Connection
BALANCED SIGNAL
FROM PREAMPLIFIER,
MIXER, ETC.
OPTIONAL INPUT TRANSFORMER
model PU-101T
With PU-101T
The pin 1 ground (shield)
The pin 2 cold (low, minus)
The pin 3 hot (high, plus)
— 13 —
Input/Output Connections
P-300M Typical Hookup
25 Volt Distribution System
The total impedance should be
mo re th a n 2.1 ohms
UNBALANCED SIGNAL
FROM MIXER,
PREAMPLIFIER, ETC.
70 Volt Distribution System
UNBALANCED SIGNAL
FROM MIXER,
PREAMPLIFIER, ETC.
The total impedance should be more
than 16 ohms
— 14 —
Installation Precaution
Input and output cables
In view of high power output produced, separate the input cable from the output cable when
installing the P-150M or P-300M. If they are in close proximity to each other, oscillation may occur.
Particular care should be given to the wiring when mounting unit in a rack cabinet.
Ground Loop
In any audio system, there are numerous ways by which ground loops can be created. For example,
they may occur when the P-150M an d P-300M are mounted in a rack cabinet, or through AC ground
when the amps are connected with preamps and mixers. These ground loops may cause hum and
noise if care is not taken during connection. An increase in noise from ground loops may be
minimized by breaking the ground loop. Generally, the chassis ground of the signal line should be
broken as shown below.
Main AC Ground
Path of
ground
Loop
When a Y cord is used, shorten the wiring to minimize noise.
A ground lift terminal is provided on the rear of the P-150M and P-300M. Removing the bar in the
terminals lifts ground.
Since the P-150M and P-300M are high power amplifiers, be careful with ventilation when they are
installed. Do not block vents on the top panel. See sketch.
Rack Cabinet
— 15 —
Installation Precaution
Mounting in an enclosed rack cabinet
The P-150M and P-300M are mountable in a standard 19" rack. When mounting, insert a 1-unit-sized
perforated panel between the units mounted, and place the same at the bottom of the rack. Be sure to
mount a perforated panel larger than 1 unit size at the top of the rack. This is required to allow
adequate heat ventilation. See illustration.
P-150M, P-300M
P-150M, P-300M
On the road use.
The P-150M and P-300M are sturdily constructed with an aluminum die-cast front panel that is
reinforced by means of an iron plate attached to its back. To ensure that strength is maintained
during their transportation from one place to another, however, you should also reinforce each unit
from the back of the rack with a special support bracket. This can be accomplished by removing
cord-hangers on the rear panel, and screws that hold the rear panel to chassis, and fitting the special
support brackets through the holes.
Top view
Side view
Special support bracket
— 16 —
Installation Precaution
Source Resistance and Damping Factor vs. Length and Size of Output
Leads
The following figure indicates that a 100 foot length of # 14 AWG annealed copper wire (two
conductor) yields a combined amplifier/cable source impedance of 0.5 ohms. A typical 8 ohms load
impedance is indicated, and this results in an effective damping factor of 15. (This damping factor is
less than the rated one of each model obtained with zero ohms cable resistance). Larger diameter
(lower wire gauge number) should be used for longer cable.
Load Protection Methods
The most common of all load protection methods
is a fuse in series with the load. The fuse may be
single, fusing the overall system, or (in the case of
multi-element speaker systems), may be multiple
with one fuse for each speaker. Fuses help prevent
damage due to prolonged overload, but provide
essentially no protection against damage that may
be done by large transients. To minimize the
problem, high speed instrumentation fuses are
recommended. For a nomograph showing fuse size
vs. loudspeaker ratings, refer to the following
figure.
— 17 —
25/70 Volt Distribution Systems
A constant voltage distribution system is a method of connecting loudspeakers to an amplifier where
the output voltage of the amplifier and the amount of power delivered to loudspeakers remain
constant.
A constant voltage distribution system is similar to a power generating station that delivers
electrical power to your home. Just as appliances can be turned on and off without affecting the
operation of other appliances connected to the electrical system, speakers can be added to, or
subtracted from, the distribution system without affecting its overall operation. However, the total
number of speakers connected to the amplifier is limited by the amplifier output power capability.
The most common voltages used in a constant voltage distribution are 25 volts and 70 volts. In most
areas of the USA, 70 volts is the maximum voltage that a pair of wires may carry without being
enclosed in metal conduit. An amplifier that is designed for use is such a system that must
develop 70 volts across the output terminal when driven to its full rated power. Actually, the
output of the amplifier swings from 0 to 70 volts in response to changes in its input signal.
In a constant voltage distribution system, "Pre-Packages" speakers with matching transformers
with several taps are normally utilized. (Each tap is designated in watts.) You may simply connect
the output terminal of the amplifier to the tap of the power rating desired. However, if speakers
without transformers are selected, the correct transformers must be carefully chosen to match the
speakers. Transformers are usually designed for a specific constant voltage level (i.e. 70 volts and 25
volts), and have primary winding taps rated in watts, and secondary winding taps rated in ohms.
They may have several primary and secondary winding taps.
Primary windings of the transformer are connected in parallel across the output terminals of the
amplifier, while secondary windings are connected across a loudspeaker or loudspeaker system.
Secondary winding taps are chosen to match the impedance of the loudspeaker. Primary winding
taps should be selected to match the power that a speaker receives. An amplifier's output voltage will
determine the power delivered to a speaker.
Transformers are connected in parallel across the output terminals of the amplifier.
Primary windings of certain transformers are rated in ohms instead of watts. To select a transformer
for a specific power level, the following formula can be used:
where Z is the impedance of the primary winding of the transformer (ohms)
For a 70 volt system, where 5 watts are desired at a particular speaker, the primary winding of the
transformer must have an impedance of:
Note: 702 is approximately 5000
E is the constant voltage level of the system
P is the desired power (watts)
— 18 —
25/70 Volt Distribution Systems
Two important factors must be considered when setting up a constant voltage distribution system.
1. The rated power of an amplifier must be higher than the total power that the speakers receive.
2. The total impedance of the speaker system must be kept above the minimum value to ensure
constant voltage operation. This impedance can be calculated by the following formula:
where Z is the total impedance of the speaker system (ohms)
E is the output voltage of the amp at full power
P is the full rated power of the amplifier (watts)
For a 50-watt amplifier to power a 70 volt system, the minimum impedance is:
(70)2 is approximately 5000
CONSTANT VOLTAGE LINES
WATTS VS OHMS VS VOLTS
WATTS
100
125
150
175
200
225
250
300
400
500
600
700
750
800
25
50
75
25V
25.0
12.5
8.33
6.25
5.00
4.17
3.57
3.13
2.78
2.50
2.08
1.56
1.25
1.04
0.89
0.83
0.78
70V
196.0
98.0
65.3
49.0
39.2
32.7
28.0
24.5
21.8
19.6
16.3
12.3
100V
9.8
8.2
7.0
6.5
6.1
400.0
200. 0
133.3
100.0
80.0
66.7
57.1
50.0
44.4
40.0
33.3
25.0
20.0
16.7
14.3
13.3
12.5
10.0
14.1
17.3
20.0
22.4
24.5
26.5
28.3
30.0
31.6
34.6
40.0
44.7
49.0
53.0
54.8
56.6
14.1
20.0
24.5
28.3
31.6
34.6
37.4
40.0
42.4
44.7
49.0
56.6
63.3
69.3
74.8
77.5
80.0
20.0
28.3
34.6
40.0
44.0
49.0
52.9
56.6
60.0
63.3
69.3
80.0
89.5
98.0
105.8
109.5
113.1
E
P
R
To use chart you will have two of the known values: ohm, volts or watts. On the first horizontal line
select one known value-watts, constant volts or resistance. Then move down the column until you
find the second known value. Then move horizontally to the unknown value.
Example 1 70V constant line and 49 ohms = 100 watts
Example 2 16 ohms and 60 volts = 225 watts
Ohms
E = volts
P= watts
R = resistance
Volts
— 19 —
Appearance
P-150M
P-300M
— 20 —
TOA ELECTRIC CO., LTD.
KOBE, JAPAN
Printed in Japan
133-02-655
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