Fuente WP210F11 - IGT G23
AC INPUT 100-240V/50-60HZ 8A MAX
DC OUTPUT: 12V 25.66A 24 12.83A
WP210F11
This is a
big one. Let’s start by breaking the circuits down into sections. The drawing
VIPER12A shows the AC coming in. No surprises here. The standard design of line
filters to keep the noise the power supply generates off the AC line. Not many
failures here. It gets rectified to generate the B+ line, about 160 VDC.
Between the negative side of the bridge and ground there is a small circuit
made of two parallel 0.100 Ohm resistors and a couple of diodes. This is our
current sensing circuit. It will generate a small negative voltage proportional
to the current on the B+ line. This will be no more than 1.2 Volts, limited by
the diodes.
Viper and Viper and VCC
Next in line we have the Viper12A that takes
the B+ line down to generate Vcc. This is the second thing that happens in
sequence. The Vcc powers other circuits to get the power supply started. This
is a high failure point. Failures can easily be troubleshot with an ohmmeter
with power off. Diodes and caps and the Viper itself are typical failures.
Troubleshooting With Power On
If you follow the suggested test procedure
power up the power supply slowly, monitoring the AC current for excessive
drain. See that B+ comes up. When B+ gets up to about 90 Volts the VCC circuit
should come up, about 15 Volts.
PFC
Just above the Viper – Vcc circuit is the
Power Factor Correction circuit. We have two parallel circuits at work in this
one. The circuits of Q104 and Q106 should come up together. Both are driven by
the current buffers Q101 and Q102. When B+ comes up, the PFC circuit (we will
cover later) should come alive.
Troubleshooting with power off
can’t tell
much other than bad caps and transistors. Problems in this area are usually PFC
drive not coming up due to a failure elsewhere in the circuit. Troubleshooting
With Power On As B+ comes all the way up, PFC should start oscillating. At the
cathode of the dual diode D106 you should see about +400 Volts. If you only get
+160 VDC or so, the PFC circuit is not working.
+400 V Line
Following D106 we have two NTC (Negative
Temperature Coefficient) thermistors and the huge reservoir caps C112 and C113.
These caps are a high failure rate. If the power supply is a few years old,
replace them as a matter of policy. These are a high stress point in the circuit.
Remember that it isn’t the line current that actually drives the game. The line
current charges up these caps in pulses. The game is powered by drawing current
off these caps. Reservoir, right? Filled in spurts at a high volume and drained
off in a constant flow at a lower current.
Over-Temperature Sensing Sensing
Just to the right of these caps we have two
resistor networks that monitor the level of the +400 Volt line and drop it down
for sensing circuits. Just below that in the schematic is a thermistor that
senses overtemperature conditions. The voltage across the thermistor should be
about 5 Volts at room temperature (25 C).
Brownout
Protect Circuitry
This
circuit generates another Vcc line that powers CTR1, one of the control boards.
It senses the B+ line for sags on the AC line. CTR1-3 is that Over-temp 5 Volt
signal mentioned earlier. This feeds to a Voltage Comparator IC101 A, pin 2.
This voltage is compared to the voltage on pin 3 (3.38 V). CTR1-1 should be 15
Volts and powers this circuit. Normally Q102 is on, giving that 15 V out
CTR1-8. This 15 Volt level is set by ZD102 and R109.
Q101 turns
on when we have an over-temp condition, U101 pin 7 low, bringing CTR1- 8 down
to less than 1 Volt. Q101 going low also turns Q1203 on. This gives a high into
IC102. IC102 (an M51957) is a delay block. A high in gives a high out of pin 6
after a delay. With a 22 µF cap, this gives
about a 7.5 second delay. Normally Q106 is off. Either of the error conditions
on the Gate will trigger Q106 on, bringing CTR1-8 down to about 5 Volts. So
CTR1-8 at 5 Volts points to one of these error conditions. Restarting will be
attempted about every seven seconds.
PFC IR1150
This chip
gets power from the same place as the Viper so it gets power early on. It is on
the CTR1 board. Pin 7 should be +15 V (Viper Vcc) you can find this on pin 1 of
CTR1. Pin 8 of the IR1150 (CTR1-4) should be oscillating. This is the Gate
Drive to the Viper. If you don’t get this, either the IR1150 is bad or one of
the control inputs is stopping it from running.
CTR1-2 is
Current Sense and should be a small negative voltage. A fraction of a volt is
good. At the bench with no load it should be close to zero, maybe -0.10 V.
CTR1- 6 is Over-voltage protect. It should be about 6 V if the 400 V line is
correct. CTR1- 7 is Feedback that monitors the +400 V line. It should be about
7 Volts if the 400 V line is good.
CTR2 12 V PWM
This is the PWM controller for the 12 Volt
regulator. An L6599. This is one of the dual output types. It alternates output
pulses between the two outputs, HVG (High Gate Drive) and LVG (Low Gate Drive).
As long as it has Vcc and no error conditions, the outputs should be pulsing.
We have all the usual pins we would expect. ISEN is the current sense input
that monitors the current through the primary of the 12 volt transformer. The
Disable (DIS) input stops the L6599 if it goes above 1.85 V. The Standby (STBY)
input stops the L6599 if it goes below 1.25 V. The Reference Output should be 2
Volts. The Line input monitors the 400 V line and should be 2.0 Volts.
12 Volt
Regulator
This is a classic example of a synchronous
rectifier. Instead of rectifiers, we have MOSFET transistors that get turned on
at the right time instead. IC103 (a GR8387) monitors the transformer output and
controls the MOSFETs. IC302 is a LT432 Voltage Reference IC. R321 and R322 form
a voltage divider that puts 2.5 Volts to the reference input of the TL432. If
the 12 Volt line goes higher, the TL432 turns on triggering the optoisolator
(IC301) informing the circuit of the voltage regulator to lower the voltage a
bit. The other part of IC301 is in the lower left corner of this same schematic
and feeds the Standby input of the L6599. So, why use MOSFETs instead of
rectifiers? If you drop a volt or two across the rectifiers it is a loss of 5%
to 10% in efficiency. While the MOSFETs only have a drop of a fraction of a
volt and a small fraction of an ohm of resistance. You will find this design
more and more on low voltage high current supplies. A 0.6 V drop in a 3.3 V
supply is an 18% loss.
CTR2 24 V PWM
This is
much the same circuit as for the 12 V side. We won’t go through it again.
24 V Regulator
This is
about the same circuit as the 12 V side but uses regular rectifiers instead of
MOSFETs.
AC_SIN_In
This
circuit puts out a 60 Hz pulse stream to the CPU for timing and monitoring the
AC line. The circuit on the left picks up the AC line. IC502 isolates the
signal and creates a power supply ground referenced pulse string. A failure
worth noting here if you only check for DC power to come up when testing these
on the bench. This circuit will not cause the DC supplies to fail. C508 and
C510 make up an AC resistor. They use the capacitive reactance as a resistance
to drop the AC line voltage down, limiting it to about 10 mA. 1/(6.28*60*.2 µF)
comes to about 13,000 Ohms, 1/(2?*F*C). IC503 senses the rising edge of the 12
Volt supply. A low out disables the AC_SIN_IN signal until 12 V is stable.
After that, the other side of IC502 gives us those 60 Hz pulses out to the
game. Failures here are the caps C508 and C510, IC502 and IC503.
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