Maintenance
Table 23: Troubleshooting the front panel – Mfg. test (cont.)
Menu Comments
Warm-up Timer
Ensures a ten-minute warm-up time for the oscilloscope before
executing the calibration procedure.
Stop Test Exits the front-panel test (Test FP) and the screen test (Test
Screen).
5. Select Test FP to start the front-panel controls test.
6. Push each button and rotate each knob to verify the operation of all controls.
If all buttons and knobs have passed the test, pushing the lower menu button
(EXIT) exits the test.
7. If any button fails to operate, inspect and/or clean the switch keypad a nd
the front panel board contacts. If cleaning does not solve the problem, the
switch
keypad, front panel board, o r M ain board may be defective. Follow the
remaining steps in this procedure to isolate the problem.
8. Repla
ce the switch keypad and retest the buttons. If the problem persists,
go to step 9.
9. Use t
he test oscilloscope and the TPP0201 probe to probe the front-panel cable
connector at J202 on the M a in board (2-cha nnel models) or J1 (4-channel
models). The following table describes the signals you should expect to see.
Table 24: Expected signals at J202
Signal at J202 Description
1 FPLED_P
LED latch line 6.44 kHz. High with 120 ns low pulses. Location of
pulse relative to FPCLR_12_P determines which lights are lit.
2 FPCLR_12_P Clear Front Panel Scan line A 6.44 kHz. Low pulsing high with
50 ns pulses. Determines beginning of a scan sequence for first
half of front panel.
3 FPCLK_12_P Front Panel Clock line A 405 kHz. High with 50 ns pulses going
low. Each clock after FPCLR_12_P increments the scan location
by one.
4 FPDATA12P
Front Panel Scan Data line A No fixed pattern. Stable when
triggered from FPCLR_12_P. Pattern depends on rotation of
knobs being scanned.
5 GND 0 V (ground)
6 FPTHERMSTR_P Front Panel Temp Sense About 2 V
DC
depending on temperature,
contrast setting, and display type.
7 FP_PWR 5.0 V
DC
8 FPTHERMGND_P Temp Sense Return Ground.
9 GND 0 V (ground)
78 TDS2000C and TDS1000C-EDU Series Oscilloscope Service Manual
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