Electronics > Repair

Repair tektronix TDS 220 no screen (white screen)


Please allow me to ask, I'm having a problem, suddenly my Tektronix TDS220 oscilloscope doesn't produce an image or a white screen, the CFL light is on. I tried checking the PIN 1 voltage (Vo = LCD Contrast adjust voltage) on the LCD connector which is equal to 0 volts, and the PIN2 voltage (Vee = Power supply for LCD (-24V)) is also 0 volts, please give me instructions and guidance on what other steps to take. what should I fix?
I really hope to be able to revive the oscilloscope.
Thank you for all the instructions and guidance

m k:
You should dig up the missing voltage.

If no schematics is available you must trace the route back the hard way.

Did you measure all the power supply voltages at the socket on the main board. The specifications for each pin are in the service manual.
If they are not correct then unplug the power connector and measure the outputs of the power supply again.

I just had something similar happen on my TDS210, Pins 1 & 2 on the display connector measured ~-6V (slowly rises from between -4V to -6V, then drops back to -4V).

Disconnecting and measuring the connector on the board results in a stable -24V, so it appeared like there's a short in the display itself. I then took the display module out of the case and measured across the 2 small 25V 3.3uF caps near the flat flex connector and found one with a 160Ohm short.

Removed that offending cap and soldered on a 50V 10uF that I had lying around, that solved the short and allowed the scope display to work again post reassembly.

Service manual I used is linked below (I did also verify the PSU voltages were fine and I had scope probe compensation output).



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