9/15/06
888-2586-001
4-37
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
b.
Second, it allows the base of Q9 to pull high, shutting it off. R62 will then pull the
gates of Q6, Q7, Q12 and Q13 low, turning them on. Q6, Q7, Q12 and Q13 are
switches which tie the 52Vdc to R48, and the supply is discharged.
4.6.2.2.4 Voltage Samples
An AC voltage sample is taken from the 48V taps using 200k ohm resistors. One from
SS_A and one from SS_B. The samples are pulsating DC with a frequency of 120Hz
and an amplitude whose average is equal to the DC power supply output. They are sent
to the PS Controller and used to control the tap switching based on the amplitude of the
pulses. The signals are also bandpass filtered at 60Hz to detect blown SCR fuses.
To determine if a tap has failed (blown fuse), refer to the Status menus in the
Diagnostics Display. A bad TAP will say “FLT” for fault.
4.6.2.2.5 Low Voltage Supply Regulators
U1, U3 and U4 regulate the voltages from the Low Voltage Supply down to 7.1Vdc,
+20Vdc and -20Vdc respectively. These voltages are sent to the controller where they
will be distributed to the individual controller boards. Input voltages to these regulators
will vary depending on the AC mains voltage.
4.6.2.2.6 16VCT, V+SCR Supply
The 16VCT secondary winding is fused by F3 and F4 on the Rectifier Board. These are
self-resetting fuses which physically look like disc capacitors. The AC is rectified by
CR10 and CR11 and becomes V+SCR which is the gate drive signal for the tap and soft
start SCRs.
4.6.2.2.7 Heat Sink Temperature
The temperature of the rectifier heatsink is monitored by Thermistor, RT1. A fault is
triggered if the temperature of the rectifier heatsink exceeds 100°C and the power
supply will be shut off. This temperature can be monitored in the Status Menu of the
Diagnostics Display. If the thermistor is shorted, the temperature reading will be about
155°C and the supply shut off. If it is open it will cause a Thermistor Fault to show up in
the fault log.
4.6.3
Power Supply ID Jumpers
JP1, JP2 and JP3 are binary ID jumpers that tell the PS Controller to which power
supply they are attached. Since all of the power supplies are identical, the jumpers can
be configured to designate the supply as PS1, PS2, PS3 or PS4. The PS Controllers
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