Crotech 3131 15Mhz dual trace Oscilloscope.

Bought from auction complete with fault, stated as no signal separation or signal display.

Switching on only one trace is visible but can be moved vertically and horizontally with say the ch1 controls but using ch2 also moves this single trace. Is the second trace generated from the first trace ?.

Anyhow taking the cover off and inspecting the main pcb i noticed immediately a new 0.25W resistor that had been soldered at one end only the other leg in the air! it being obvious the original resistor that lived their had been snipped out and this new resistor soldered to one end of the protruding pigtail, This resistor (R3) had a value of 0.68 omn's (safety resistor?) i then had the temptation to solder the other resistor leg into place but decided against this as a little scorching was present where the original had been roasted!.

The moral of this tale is: I need advice i also need a cct diagram to further investigate this fellows fault so can anyone here help so that other trace can be restored

Hello there, are you still looking for info on this scope? I have just repaired the same one now with the same fault, I traced it down to a single Tant bead capacitor gone short circuit causing a 6.8Ω resistor to burn out, fixed now and its working good!
Please let me know if you want the schematics I will have to scan the manual for you,
Wayne.

Hi Wayne,
I still have this Scope and i would be delighted and grateful if you would scan the schematics for me.

Thank's xl5

crotech 4000

Crotech 3131 - Not Powering up

Hi,

I have a Crotech 3131 which was working fine, but is now faulty. The fault started when I plugged in the trace would come up and then shut down in about 10-15 seconds. Now no power is coming to the oscilloscope. I have identified one disintegrated resistor in the HV board, but I can't identify the value of the resistor. Still couldn't find any faulty capacitors in the main power supply board. I would really appreciate if anybody can advice me on how to diagnose the problem, and also would be great if I can get hold of the schematics if someone has it.

Many Thanks..