Local Ride-Through Power; Processor Board Connectors; Isolation Transformer; Elevation Relays - GE T2100 Service Manual

Unregulated power for the isolated power comes from the center tapped isolation
transformer, the non-isolated power comes from the 24V power supply. These are
both fed through the full-wave bridge to the switching regulator.
The switching regulator is a step-down, buck PWM-type that switches at about
100 KHz. It also has an internal current limit of 4 amps. The 5-volt regulators are
configured to produce about 5.1 volts.

Local Ride-Through Power

Located on the power board are 3 Ultracapacitors. They are fed by the isolated
switching power supply. These capacitors provide 3.3 Farads of capacitance that give
the processor board power to logically power down activities in case of a loss of
power to the T2100 Treadmill.

Processor Board Connectors

The power board has two connectors that directly interface with the processor board.
The first, a 3-pin power connector provides +12V Unregulated power, +5V isolated
power and isolated ground to the control side of the processor board. The 10-pin
ribbon cable provides a signal interface 24V power, as well as +5V non-Isolated power
and a non-isolated ground connection.

Isolation Transformer

The isolation transformer provides isolation for the secondary. The 220 VAC primary
is stepped down and isolated from the 12V (CT) secondary. The secondary provides
+12V unregulated power for a 5-volt switching supply.

Elevation Relays

A direction control and an enable relay control the elevation motor. A change in
direction should only occur when the elevation motor is stopped. The enable relay is
disabled by the normally-closed limit switches at the end of travel to prevent damage
to the motor. The LIMIT* signal goes low when a limit switch is activated in a particular
direction.

Elevation Sensor

The elevation sensor is a 5-turn pot that is coupled to the elevation rack. The
voltage on pin 2 should be proportional to elevation. That is, low voltage should
be low elevation, increasing voltage should indicate increasing elevation. During
self-calibration, the offset and gain remain in software memory. Initially, the limit
switch positions are the reference for self-calibration. Once the offset and gain are
adjusted, the pot position determines the elevation.

ESD and EMI Compatibility

The I/O connectors on the power board have current-limiting resistors, zener diodes,
or filtering capacitors wherever possible to prevent EMI from escaping the board.
These components also limit rise-time and voltages which may come from ESD
or other noise sources.
2021403-120F
T2100 Treadmill
Theory of Operation
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