Maintenance
6–42
TDS 200 Series Digital Oscilloscope Service Manual
5. If the 1270 V
pk-pk
signal is missing, the power supply module is probably
defective. Replace it.
Follow these steps to troubleshoot a nonfunctional display.
1. Remove the rear case using the procedure Rear Case on page 6–14.
2. Turn the instrument on.
NOTE. Without a functional display module, the simplest way to verify that the
instrument is on and functioning is to check for a signal at the PROBE COMP
output. The PROBE COMP output generates approximately a 5 V, 1 kHz
squarewave.
3. Use the test oscilloscope and set the Attenuation switch to 10X on the P2100
probe to probe the display cable connector at J202 (two channel instruments)
or J102 (four channel instruments) on the main board. The table below
describes the signals you should expect to see.
Signal at J202/J102 Description
Pin 1 (marked with A ) –10 VDC to –22 VDC
Pin 2 –23 VDC to –25 VDC
Pin 3 Digital data, high = 5 V, low = 0 V
Pin 4 Digital data, high = 5 V, low = 0 V
Pin 5 Digital data, high = 5 V, low = 0 V
Pin 6 Digital data, high = 5 V, low = 0 V
Pin 7 0 V (ground)
Pin 8 0 V (ground)
Pin 9 +5 V
DC
Pin 10 1.89 MHz clock (528 ns period), ≈ 50% duty cycle, appears
in bursts, high = 5 V, low = 0 V
Pin 11
19.3 kHz clock (51.7 ms period), ≈ 16% duty cycle,
high = 5 V, low = 0 V
Pin 12 (closest to BNC end of
instrument)
75.5 Hz clock (13.2 ms period), ≈ 0.4% duty cycle,
high = 5 V, low = 0 V
4. If all the signals are present, the display module is probably defective.
Replace it. If all or some of the signals are missing, continue with step 5.
Display Troubleshooting
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