4-32
888-2586-001
9/15/06
WARNING: Disconnect primary power prior to servicing.
Platinum Z16HD+
Section 4 Overall System Theory
4.6.1.2
Rectifier Board Circuit Description
Refer to the Rectifier Board schematic and Figure 4-13 for the following. The Rectifier
Boards perform three primary functions:
•
Dynamic secondary tap switching using SCRs, to maintain a relatively constant sup-
ply voltage and thus maintain constant transmitter power output despite fluctuations
in the 3 phase AC line voltage.
•
PA Power Supply Soft-Start.
•
PA Power supply Discharge.
4.6.1.2.1 Tap Switching Circuit Operation
The control signals for the SCRs are active high and come directly from the PS
Controller Boards. They enter the “B” Rectifier Board on each power supply at:
•
J4-1 - DRIVER 1 = TAP 1 (activates SCRs for 48V tap)
•
J4-3 - DRIVER 2 = TAP 2 (activates SCRs for 50V tap)
•
J4-5 - DRIVER 3 = TAP 3 (activates SCRs for 52V tap)
•
J4-7 - DRIVER 4 = TAP 4 (activates SCRs for 54V tap)
NOTE:
The circuit for the 48V tap will be explained here as the other three are identical,
but are attached to different transformer secondary winding taps.
The DRIVE_1 signal is used to activate the 48Vdc secondary tap. This tap is designated
TAP 1 in the Diagnostics Display. When active (HIGH) it causes the output of U2-17 to
go low. This turns on Q28 which applies 10VB-SS, now called DRIVE_1, to R12 on the
“B” side of the 48V section. Interconnect cable J3 then connects the same signal to R25
on the “A” side Rectifier Board 48V section.
NOTE:
The 10VB-SS (SS = Soft Start) will only be present if the DISCHARGE signal at
J4-6 is inactive. See PA Power Supply Discharge later in this section for more
information.
The 10VB-SS forward biases diodes CR4, CR8 and CR12 on the “B” side and CR13,
CR17 and CR21 on the “A” side. This turns on the associated SCRs, Q4, Q8 and Q12
for the “B” side and Q13, Q17 and Q21 on the “A” side. Each of the SCR anodes are
tied to ground with the cathode connected through a 30 amp fuse to a tap on one of the
transformer secondaries. The “B” side is connected to L5, M5 and N5 with the “A” side
connected to L4, M4 and N4 (see the Overall System Block Diagram for these
Summary of Contents for Platinum Z16HD+
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