Troubleshooting

First look at the communication log at the bottom left of the GUI (logs/gui_YYYYMMDD.log) to see which command returned what.

Cannot connect

Symptom	Fix
Scope: cannot connect, or shows "Connected" but settings are not applied	Set the resource name to VICP::<scope IP>::INSTR (IP: Internal information). On the scope, check the control method (TCPIP (VICP) or LXI (VXI11)) and IP under Utilities → Utilities Setup → Remote. If ping works, VICP should connect. On connect, the *IDN? response is verified; if there is no response, VICP ⇔ VXI-11 is tried automatically before reporting an error
Stage: ping works but the connection times out	The TCP port number does not match the controller setting. Enter <stage IP>:<port> in the address field, using the values in Internal information. If a previous session is holding the connection, restart the controller. If it connects but does not respond, check the SHOT-compatible mode and the delimiter (CRLF)
Stage: ping fails after a network change (the scope responds)	Check that the control PC's subnet mask is 255.255.255.0 (Initial device settings). Check in the controller settings that the SHRC-203's subnet mask and gateway put it on the same network as the PC, and power-cycle the controller after changing its settings (they do not take effect until restart). To check that no other device has the same IP, look at arp -a in a terminal on the PC. Addresses are in Internal information
Laser: cannot connect	Check the COM number in Device Manager (COM5 on the control PC). Check that the FTDI VCP driver is installed
Camera: no image	Try a different [Device] number (default 0)

No signal or strange signal

Symptom	Possible cause	Fix
No signal at all	The laser is not emitting	Check that the laser panel status shows the red "Emission: ON" bar
	The beam is on an electrode (metal)	Jog Y by a few tens of µm to put the beam on silicon
	No bias applied	LV 6.0 V and HV (−190 to −195 V at 33 °C). Check that the LV OUTPUT lights blue and that the HV bias is ON (red button)
	Wrong horizontal offset	Set it to −53 ns with [★ Apply Standard Settings ★]
Waveforms update but are flat	After a rep-rate change, TUNE fell below the lasing threshold (TRIG OUT keeps coming)	Redo TUNE optimization. For a quick check, set TUNE to auto
Amplitude differs from expectation	The camera light is still ON, the rep rate is not 1 MHz, or the alignment is off	Turn the light OFF and check 1 MHz and TUNE 50 %. If it still differs, match it with TUNE optimization
In a scan the signal on the electrode does not drop to 0, or the rise at the electrode edge is gradual	Defocus, or a coordinate offset	Redo origin finding (check Z)

Stage and alignment

Symptom	Fix
"Machine coordinates: unknown" is shown and you cannot go to the saved origin	The GUI lost track of the machine coordinates (M-ORG from the JS-301, controller restart, interrupted homing, etc.). Run [Mechanical Home (H:W)] from the GUI
Origin finding stops with "No clear dip" or "No clear edge"	Check that the beam is on the reference strip, 50–200 µm inside its end, that the laser is ON, and that a signal is visible; then run again
"Valley too shallow", or the Z valley cannot be found	Widen the Z range to ±30–50 µm, or roughly focus with the camera first, then run again
The Z residual of the full calibration exceeds a few µm, or the coefficients changed a lot since last time	Run it again, or use the "Measured Z" mode for Z tracking in the scan
After origin finding or full calibration the right column becomes wider, or the tilt coefficient display is stale	Bug in an older version (fixed in the 2026-10 revision). Use the latest version
The jog direction does not match the camera image	The camera or stage mounting orientation was changed. Fix stage_screen_dir in config_local.json

Scans

Symptom	Fix
Aborted with "saved files are not increasing"	The scan stops automatically if the number of files on the scope does not increase for 2 points in a row. Check the scope's Save Waveform setup and the save folder
timeout lines in the scan log	Acquisition did not finish in time. Check that the laser is ON and that the EXT trigger is firing. Also check that [Averaging OFF] has not been unchecked
Warning at start that "Z is 30 µm or more away"	Check that this is intended. Origin finding may not have been done, or the Z tracking mode may be wrong

Data retrieval

Symptom	Fix
SSH connection fails	Check that the scope is on and responds to ping, that the OpenSSH server on the scope is running, and that the password is correct
A "conflict" is reported	A file with the same name but a different size exists on the PC. It is not overwritten; check which one is correct and clean up manually
Cannot transfer during a scan	By design (mutually exclusive). Transfer after the scan finishes

Camera

Symptom	Fix
The image is completely dark or completely white	Adjust [Gain] on the camera panel (the communication log shows the actual value, so you can see whether it took effect; if the actual value does not change, the camera does not support it). If that does not help, adjust the illumination brightness and the lens aperture

General TCT problems

Problems common to other TCT setups

Symptom	Possible cause	Check / fix
Oscillating waveform (ringing)	Impedance mismatch, long cables	50 Ω termination, shorten cables and wire bonds
Saturated or clipped waveform	Input range of amplifier or scope exceeded	Widen the vertical range, reduce the laser intensity
Pulse shape changes with intensity	Too much charge generated (plasma effect)	Reduce the laser intensity
Large noise	Ground loops, external pickup	Use a single ground point, check shielding
Signal drifts over time	Laser intensity or temperature fluctuations	Re-measure a reference point regularly
Leakage current jumps	Breakdown	Ramp down immediately

Please contribute

Add any problems you actually ran into, and how you solved them, to this page (Contributing).