Assembly Instructions Chapter 4

4-6 kW UHF Translator Chapter 4, Circuit Descriptions
837B, Rev. 0 4-29
board. The -12 VDC connects to the
board at J4-5 and is filtered and
isolated by L9 and C21 before it is
connected to the rest of the board.
4.2.13 (A3)+12V(4A)/-12V(1A)
Power Supply Board (1265-1312;
Appendix D)
The ±12-volt power supply board
consists of three separate power
supplies, two of which produce the +12
VDC and one for the -12 VDC needed
to power the circuit boards in the
exciter tray.
4.2.13.1 +12 VDC Power Supply
The 18 VAC from the external step-
down toroid in the tray connects to J1,
pins 7 and 8. The 18 VAC connects
through 7-amp fuse F2, for over-
current protection, to two full-wave
bridge rectifier circuits.
CR1, CR2, CR3, and CR4 rectify the AC
that is then filtered by C2 and
connected to U3 and U4; U3 and U4
are voltage-regulator ICs for the +12
VDC. The voltage-regulated and
current-limited +12-VDC output of U3
connects to J4, pins 1, 2, 3, and 4,
which is one of the +12-VDC outputs of
the board. The green LED DS3 will be
lit if +12 VDC is present to J4; C7 and
C8 are bypass capacitors. The +12 VDC
output of U4 connects to J5, pins 1, 2,
3, and 4, which is another one of the
+12-VDC outputs of the board. The
green LED DS4 will be lit if +12 VDC is
present to J5; C9 and C10 are bypass
capacitors.
CR5, CR6, CR7, and CR8 rectify the AC
that is then filtered by C1 and
connected to U1 and U2; U1 and U2
are voltage-regulator ICs for the +12
VDC. The voltage-regulated and
current-limited +12-VDC output of U1
connects to J6, pins 1, 2, 3, and 4,
which is one of the +12-VDC outputs of
the board. The green LED DS1 will be
lit if +12 VDC is present to J6; C3 and
C4 are bypass capacitors. The +12-
VDC output of U2 connects to J3, pins
1, 2, 3, and 4, which is another one of
the +12-VDC outputs of the board. The
green LED DS2 will be lit if +12 VDC is
present to J3; C5 and C6 are bypass
capacitors.
4.2.13.2 -12 VDC Power Supply
The 18 VAC from an external step-
down toroid connects to J1, pins 1 and
4, of the board and is wired to CR9,
CR10, CR11, and CR12 which form a
full-wave bridge rectifier network for
the –12-VDC power supply. F1 is a 3-
amp fuse that provides over-current
protection. The rectified output is
filtered by C11 and fed to U5, the
voltage-regulator IC for the -12 VDC.
The voltage-regulated and current-
limited -12 VDC is connected to the
-12-VDC output jacks J7, pins 5
through 10, and J8, pins 5 through 10.
The green LED DS5 will be lit if -12
VDC is present to J7 and J8; C12 and
C13 are bypass capacitors.
4.2.14 (A15) x8 Multiplier Enclosure
(1265-1347; Appendix D)
The x8 multiplier enclosure is an
aluminum box that provides RFI and
EMI protection for the x8 multiplier
board (1227-1002) that is mounted
inside of it. This protection is needed to
prevent any interference from
obstructing the upconversion process.
The output from the channel oscillator
at +5 dBm enters the enclosure at J1.
The oscillator signal is multiplied and
amplified by the x8 multiplier board to
+16 dBm and sent out of the enclosure
at J2.
The +12 VDC needed to operate the
board enters the enclosure through FL1
and connects to J3-3 on the board. The
return for the +12 VDC enters the
enclosure through E1 and connects to
J3-4 on the board.