How do all these parts work together?
Reference ED-286060 for this discussion. Beginning at the top left, the External Interlock signal is optically isolated using an HCPL2631 (A106) The input circuit R113, R116 and Z103 provide some protection against over voltage and polarity errors from the outside world. When a logic high level is present at the External Interlock plug Q104 is saturated and collector is near 7V. A modification to add a latch to this signal is kluged on the PCB using section 'D' of U102. The latched signal returns to R105, D115 and D123. This level is applied to the positive terminal of the resistive soft-start relays and also allows the soft-start circuit to activate through D115. Q100 controls the return path for the relays and if it is allowed to turn on, the AC power will be applied to the main transformer in a soft-start manner.
Soft-Start works by connecting the main transformer to the power line first through some resistors that limit the current and then directly via solid-state relays. Without this step-start the main breaker would trip due to the high magnetization current that sometimes occurs in the transformer.
The AC power to the relays is controlled by three conditions. The first is the External Interlock. If there is a problem in the racks the interlock drops and the high power in the supply is removed. A second condition that removes power is a high temperature. Thermo switches are mounted on all the water-cooled plates and if there is no water and the normal protection fails this backup system will prevent meltdown. Finally there is a circuit that monitors the outputs of each regulator and if the voltage exceeds the trip point for more than 10mSec the high power is removed.
The control board provides six (6) voltage rails for all the electronics in the supply. There is a +5V logic supply, a +/-15v and +/-20V analog supplies and a separate +5V for the readout board. These supplies use standard three terminal regulators. The 20V outputs however are 5V regulators that ride on top of the 15V regulators, i.e. their ground pin is connected to the 15V rail. There are two kluges added to these regulators. First there are two 1-Ohm resistors added between the rectifiers and the regulators. This limits the in-rush current. The second additions are protection diodes across and at the output of the regulators.
The final circuit on the board monitors the three phases into the supply. D112, R108, C107 and Z101 produce a logic level on R101. U100 then conditions this level and it is sent to latch U102. Three identical circuits provide the three phase monitoring.
Reference ED-286062 for this discussion. The display board contains the LEDs for user feedback of the supply status. Most of the indicators are Red/Green LEDs that are always illuminated. This prevents missing information, if the LED is not lit it is broken. The red/green LED is controlled with two open collector inverter gates. When one gate is on the other is off. The gate that is on pulls that lead of the LED to ground. Current flows from Vcc through a resistor on the opposite lead through the LED to ground. For the other state the flow reverses. The resistors control the brightness of the LED and are slightly different for the Red as for the Green
The reset lights have a pulse stretcher (one-shot) so the signal can be seen.
Five Red LEDs directly monitor the control power rails.
Reference ED-286082 for this discussion. The fault board does two basic things. First it is where the analog signals are made for remote monitoring. A 37pin 'D' style connector is mounted to the back of the supply for this purpose. The second purpose of this board is fault detection for over current, temperature and voltage. There is also an under voltage trip on each regulated output
The current and temperature trips are simple comparitors that compare to a preset reference. Since the voltage trip looks at over and under voltage set points that is some additional circuitry needed. The under voltage circuit is only activated when the outputs are ON. To do this the turn-on ramp from the regulator board is compared. When this ramp exceeds the 10V reference the enable on the under voltage comparitor circuit is activated.
Trip levels are hardware controlled with two resistors for each regulated output. The current trip level resistors are socketed to allow changing their values without desoldering them from the board.
Reference ED-286084 for this discussion. The logic board controls all logical aspects of the supply. The main function of this board is holding fault trip status. The fault signals from the Fault board are latched by the 74LS279 RS flip-flops. The output of each FF is multiplex onto the digital output connector. The multiplexing is controlled by the word count signal that comes from the Rack Monitor chassis. This scheme provides up to 8 x 16-bit words of digital information to be transmitted over one Rack Monitor connector per supply. Three supplies and then be bused together on one cable to communicate digital status. U1 on page 3 of the schematic does the word decoding along with the proper Module Select plug on the J7 NUMBER socket.
The over voltage timeout circuit will remove the high power from the main transformer if any overvoltage fault is present for longer than about 40mSec. A one shot, U43, is fired when an over voltage occurs. The same signal is applied to the J input of the JK-Flip-Flop, U47. If the signal is still there after the one-shot times out the FF is set and the high power is removed. If the signal goes away before the one-shot times out the FF remains clear.
A modification was made to the Logic Board for the RunII BLS supplies. Using a spare gate in U31 any output that faults will cause all the outputs, for that half, to turn off. This prevents having electronics from being powered when some rails are missing.
Reference ED-286072 for this discussion. AC power is first applied through a magnet circuit breaker/switch. The solid-state relays must be activated before the main transformer gets any power. The control board, however, powers when the breaker is closed.
All secondaries of the transformer are full wave rectified with Schottky diodes. The rectifiers are in contact with a water-cooled plate. Capacitors are needed to low the impedance and reduce the ripple voltage.
Reference ED-286076 for this discussion. The Regulator board contains regulator circuitry, voltage and current monitoring and on/off circuitry. The circuit board layout is in three similar sections that run the length of the board. Each section operates a pair of regulators for positive and negative voltages. The first section, for outputs A&B, have reference designators in the 100s. The second section, C&D, has reference designators in the 200s and section three has 300s. This helps trouble shooting since components, such as A100, A200 or A300, have the same functionality for each section.
On page 1 Q107 and A103 are the active components for the on/off circuit. When the supply is commanded OFF, Q107 is on and the output of A103 is one diode drop below ground. This level connects through D101 to the reference diode VR1 whereby bringing it to zero volts. The output regulates at the reference level which is zero when OFF. When the supply is commanded ON A103 is a simple integrator and the output begins to ramp linearly toward the supply rail. D101 clamps the reference level to this ramp until the ramp exceeds the reference and the diode is reverse biased. The reference diode now take over at a fixed 10V level. The circuitry around Q101 make a current source for the reference diode.
The heart of the regulator is A100, pin 3 connects to the reference and pin 2 receives the voltage feedback from the output. An error signal is formed that either add or subtracts current on the base of the pass-transistor. Q105 and surrounding components make a current source that along with the current supplied by A100 will sufficiently drive the pass transistor/s. R100, R101 and R102 divide the voltage feedback signal so pin 2 is at the reference level and the voltage monitoring circuitry, A101:A,:B receives a 5V level. If the supply output is above 10V the reference is used directly and the feedback is 10V nominal. If the supply output is below 10V then the feedback level is 5V and the reference level is divided to 5V nominal.
A101:A is a differential amplifier with a gain of -1 and A101:B is an inverting amplifier with gain if needed. Only outputs less than 5V will need gain. The output is used by the fault circuit and analog monitoring. Note: If the monitoring pin on the analog connector is shorted or pulled with an impedance of less than 1MegOhm the voltage or current feedback will be altered. This can cause the supply to malfunction. For example if the Rack Monitor chassis is not powered on the analog connector is no longer high impedance and will cause the supply to fault on undervoltage.
A107 is an instrumentation amplifier that connects across the output shunt. A102 provides gain to bring the shunt signal up to 5V when the current full scale. There is a redundant protection circuit that limits the output currrent in the event the normal over current trip circuit fails. Q100 will begin to sink current away from the base of the pass transistor/s.
The negative regulator circuitry is identical to the positive one except for the polarity of the components.
The Regulator board has three connector along the bottom that connect to the output modules. The base drive and feedback signals are passed through these connectors. The top of the board has a power connector and a ribbon connector. The ribbon connects to the Fault board.
Reference ED-286079 for this discussion. The front panel top right side has the control switches for the supply. The center switch transfers On/Off control from the front panel to the computer. The right and left side switch turn the supply On and Off if the center switch is down (LOCAL). Each side is controlled separately. The reset switches are not controlled by the center switch and function any time. Pressing the reset button while the supply is on has no ill effect.