Theory of Operation
Chapter 3: Theory of Operation
Page 3 - 6
TranStar® PC-100/PC-200/PC-300/PC-350/PC-400/PC-450/
PC-500/PC-550/TR-500/SG-500/OB-450/OB-550/EL-550
Series Stretcher Service Manual (man115re)
Theory of Operation
Control Board
The control board contains the necessary analog and digital circuitry to govern
powered bed movement as outlined in this manual.
Power Supply
Connector P5 is the AC power input.
WARNING:
Fuses F1 and F3 protect the stretcher’s electrical system. For 120V AC
power, a 6.30A UL 198G time-lag fuse should be used. For 230V AC, a
2.50A IEC 127.3 time-lag fuse should be used. Check the assembly
drawing or schematic for the proper Hill-Rom fuse. Personal injury can
occur.
Resistors R37, R39, and R40 are used to configure the primary coils of the
transformer (T1) for series or parallel connection. R37 and R40 provide
parallel connection for a 120V AC input. Only R39 provides series connection
for a 230V AC input.
The transformer full load rated output (as configured for this supply) is 15V
rms at 670mA rms.
The PTC overcurrent protection device, R38, protects the secondary circuit
and raw supply from overloads. This component is necessary for regulatory
approval.
Diodes CR21 - CR24 and capacitor C21 rectify and filter the transformer’s
secondary output.
Q1 reg12 +/- 0.5V DC. Maximum output current for this application is
approximately 250mA. Q1 can maintain regulation with an input voltage down
to 14.6V DC.
The transient voltage suppressor, CR20, protects the load from overvoltage
conditions.
The capacitor, C11, filters out noise.