Regulated Lh Supplies; Regulated S Supplies - Fluke 5700A Series Service Manual

Table 2-10. Regulated Outputs from the Regulator/Guard Crossing Assembly
Nominal
Signal Name
Output
+15 OSC +15V
-15 OSC -15V
+5RLH +5.975V
+5LH +5.1V
-5LH -5V
+44S +44.15V
-44S -44.15V
+17S +17.000V
-17S -17.000V
15S -15V
+30FR1 +30.96V
+30FR2 +30.96V

2-73. Regulated LH Supplies

LH COM is the return path for the +5RLH, +5LH, -5LH and +8RLH supplies. The
+5RLH, +8RLH, and +5LH supplies use the unregulated +5LHR supply from the Filter
assembly. The +5RLH supply uses three-terminal TO-3 regulator U11 with heat sink,
bypass capacitors C20 and C21, protection diodes CR17 and CR20, and the diode
combination of CR34 and CR35. The +5LH supply uses three-terminal TO-3 regulator
U8 with heat sink, bypass capacitor C16, protection diodes CR14 and CR16, and resistor
R13. The -5LH supply uses the unregulated -5LHR from the Filter assembly and consists
of three-terminal TO-220 regulator U12 with heat sink, bypass capacitors C23 and C24,
and protection diodes CR21 and CR24. Capacitors C16, C21, and C24 improve the
stability of U8, U11, and U12 respectively. Diodes CR14, CR17, and CR24 protect the
regulators from input shorts. Diodes CR16, CR20, and CR21 protect the regulators from
reverse voltage. Resistor R13 and diodes CR34 and CR35 increase the output of
regulators U8 and U11. The unregulated +8RLH supply is generated by fusing the
unregulated +5LHR supply from the Filter assembly with 3.15A slow-blow fuse F1.

2-74. Regulated S Supplies

Line S COM is the return path for the +44S, -44S, +17S, -17S, +15S and -15S supplies.
Line S COM is also connected to LH COM. The +44S supply uses the unregulated
+44SR from the Filter assembly. This supply uses three-terminal TO-39 regulator U10,
Q2, VR3, VR4, VR5, R20, R14, R15, CR18, CR19, CR25, C17, C18, C19, C65, PTC
resistor R60. The regulator IC (U10) provides the current and thermal limiting. Its
regulated output voltage is set by R14 and R15, yielding a nominal output of +44.15V.
Components Q2, R20, VR3 and VR4 act as an emitter follower to protect the regulator
against a potentially excessive input-output voltage differential in the event of a short
circuit. Capacitor C65 filters this voltage to the regulator. Diodes CR19 and CR25 protect
the regulator against shorts at the input, while CR18 protects the regulated output from
reverse voltage. Capacitors C17 and C18 are for bypass. Capacitor C19 improves
rejection of input variations. Components U10 and Q2 have heat sinks to provide thermal
protection for both normal and short-circuit conditions. The regulator is shunted by R60
and VR5, which normally pass 28 mA of current to remove the power from the regulator.
Tolerance Current
Limit
+/-800 mV 2A
+/-800 mV 2A
+/-425 mV 2A
+/-300 mV 2A
+/-300 mV 2A
+/-2.03V 0.5A
+/-2.03V 0.5A
+/-475 mV 4A
+/-835 mV 6A
+/-800 mV 2A
+/-1.7V 1A
+/-1.7V 1A
Theory of Operation
Analog Section Detailed Circuit Description
Rated
Output
200 mA
200 mA
600 mA
600 mA
400 mA
140 mA
140 mA
1.0A
1.0A
300 mA
85 mA
85 mA
2
Test Point
TP3
TP5
TP14
TP11
TP15
TP13
TP16
TP8
TP12
TP19
TP2
TP7
2-39