Service manual

Revision D 4-5
Troubleshooting : Power PCB Theory
Series 2000 Treadmill
409110-004
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.
Isolation Transformer
The isolation transformer provides isolation for two secondaries. The
220 VAC primary is stepped down and isolated from the two 12 VCT
secondaries. Each of the secondaries provide unregulated power for a
5-volt switching supply.
Power Supplies
There are two identical power supplies. One is for the control power, the
other is for the isolated serial link. The isolated serial link supply
provides a maximum of 2 amps of 5-volt power to operate a manual
controller.
Unregulated power comes from the center-tapped isolation
transformer, 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.
Isolated Serial Link
This circuitry provides an isolated, RS-422/232 link back to the
controlling system. It also provides up to 2 amps of 5 V power for an
external manual controller.
Debug/Serial Link
The debug/serial link connector is covered by a removable plastic plate.
This connector sends/receives the analog outputs, the manual analog
inputs, and the RS-232 (debug) signals.
NOTE
These outputs are accessed through the
SERVICE connector and are referenced to
DIGITAL ground which is NOT connected to
CHASSIS ground. Analog isolation
amplifiers may be required to protect
externally connected equipment.