1L5/Repairs: Difference between revisions
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(Created page with "I obtained a nonfunctioning 1L5. The output was a flat line, no deflection. The sequence of steps was as follows. # Confirm that the 5kHz calibration source is functioning by...") |
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The output was a flat line, no deflection. | The output was a flat line, no deflection. | ||
The sequence of steps was as follows. | The sequence of steps was as follows. | ||
# Confirm that the | # Confirm that the 5 kHz calibration source is functioning by setting the VOLTS/CM switch to the CALIBRATE position and measuring the voltage waveform at terminal BP on the calibrator board. | ||
# Confirmed that the the first LO is functioning. I connected the front panel OSC OUT to a frequency counter, put the VERTICAL DISPLAY switch in LIN position, set Hz/CM to 200, and set the sweep mode to MANUAL. I confirmed that first LO could be swept by rotating the MANUAL knob and watching the counter. | # Confirmed that the the first LO is functioning. I connected the front panel OSC OUT to a frequency counter, put the VERTICAL DISPLAY switch in LIN position, set Hz/CM to 200, and set the sweep mode to MANUAL. I confirmed that first LO could be swept by rotating the MANUAL knob and watching the counter. | ||
# Checked the output of the first IF amplifier, saw no signal. | # Checked the output of the first IF amplifier, saw no signal. | ||
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# Checked the output. Still no deflection. Note: When using the internal calibration source, deflection should be maximized when the first LO (and OSC OUT) frequency is 2995 kHz. | # Checked the output. Still no deflection. Note: When using the internal calibration source, deflection should be maximized when the first LO (and OSC OUT) frequency is 2995 kHz. | ||
# Checked the output of the variable resolution amplifier. Looks good. | # Checked the output of the variable resolution amplifier. Looks good. | ||
# Put the 1L5 VERTICAL DISPLAY switch in VIDEO mode, which sends the input signal to the mainframe, like a regular amplifier plug-in. The VIDEO mode output is good. | # Put the 1L5 VERTICAL DISPLAY switch in VIDEO mode, which sends the input signal to the mainframe, like a regular amplifier plug-in. The VIDEO mode output is good. 5 kHz is appearing at the mainframe. | ||
# Put the 1L5 VERTICAL DISPLAY switch into LIN mode. | # Put the 1L5 VERTICAL DISPLAY switch into LIN mode. | ||
# Checked the voltage waveform at the collector of Q400 in the output amplifier circuit. Looks good. | # Checked the voltage waveform at the collector of Q400 in the output amplifier circuit. Looks good. | ||
# Checked the DC level at the collector (can) of Q410. It was close to the + | # Checked the DC level at the collector (can) of Q410. It was close to the +350 V rail, and the transistor was cold. | ||
# Wiggled Q410 in its socket (with the power off). | # Wiggled Q410 in its socket (with the power off). | ||
# Checked the DC level at the collector (can) of Q410. It was 165V. | # Checked the DC level at the collector (can) of Q410. It was 165V. | ||
# Checked the output of the 1L5. Now deflection works. | # Checked the output of the 1L5. Now deflection works. | ||
The 1L5 is functioning. Of course it needs to be calibrated. | The 1L5 is functioning. Of course it needs to be calibrated. | ||
[[Category:Instrument repair reports]] |
Latest revision as of 01:54, 1 March 2021
I obtained a nonfunctioning 1L5. The output was a flat line, no deflection. The sequence of steps was as follows.
- Confirm that the 5 kHz calibration source is functioning by setting the VOLTS/CM switch to the CALIBRATE position and measuring the voltage waveform at terminal BP on the calibrator board.
- Confirmed that the the first LO is functioning. I connected the front panel OSC OUT to a frequency counter, put the VERTICAL DISPLAY switch in LIN position, set Hz/CM to 200, and set the sweep mode to MANUAL. I confirmed that first LO could be swept by rotating the MANUAL knob and watching the counter.
- Checked the output of the first IF amplifier, saw no signal.
- Checked the voltage waveform at the base of Q30, saw no signal.
- Wiggled Q20 in its socket.
- Checked the voltage waveform at the base of Q30. Signal look just like in the manual.
- Checked the output. Still no deflection. Note: When using the internal calibration source, deflection should be maximized when the first LO (and OSC OUT) frequency is 2995 kHz.
- Checked the output of the variable resolution amplifier. Looks good.
- Put the 1L5 VERTICAL DISPLAY switch in VIDEO mode, which sends the input signal to the mainframe, like a regular amplifier plug-in. The VIDEO mode output is good. 5 kHz is appearing at the mainframe.
- Put the 1L5 VERTICAL DISPLAY switch into LIN mode.
- Checked the voltage waveform at the collector of Q400 in the output amplifier circuit. Looks good.
- Checked the DC level at the collector (can) of Q410. It was close to the +350 V rail, and the transistor was cold.
- Wiggled Q410 in its socket (with the power off).
- Checked the DC level at the collector (can) of Q410. It was 165V.
- Checked the output of the 1L5. Now deflection works.
The 1L5 is functioning. Of course it needs to be calibrated.