Saturday, December 23, 2017

OS-5020, Kiotto, LG, EZ, Oscilloscope - Info and placeholder

I have a broken Kiotto OS-5020 to fix, that was my first oscilloscope,  suspect the problem is on the power supply. Making here a placeholder for information related to this scope while I don't have the opportunity to fix it (it's in Portugal).

In the past I tried to reach the local distributor in regards to get the schematic or additional info but got no reply for the two email's sent... so on the good Portuguese tradition.. have a finger and don't count with me to get any more equipment from your business.

I already did before some troubleshooting to suspect the power supply even without schematic but to no success at that time.

This scope comes with many different brand names, here's some examples from the web:

Kiotto (local Portuguese re-branding by "Niposon" distributor):

Goldstar:

EZ



The schematics:

- https://www.scribd.com/document/134639836/LG-OS-5020G-Oscilloscope-Service-Manual

- http://www.testequipmentdepot.com/ezdigital/pdf/os5020-5020c_manu.pdf

Here some good description also with schematic in multiple pdf's:

http://timhatch.com/projects/os-5020g/


Another slightly different unit (9020) but I suspect very a similar schematic:

- http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Goldstar/OS-9020P.pdf


And the OS-9020 version with similar symptoms but same resolution:

- http://charliexray.blogspot.ie/2010/07/osciloscopio-goldstar-os-9020p.html

 The "common" problem with the unit looks like on the negative rail power due to a resistor/fuse, that causes a smaller horizontal trace and no vertical deflection.
In my case I eared a small "bang" when the issue occurred, at power on of the unit, but never found any damaged component on a first glance.

Bellow some posts with matching images (from the post) on troubleshooting of the power unit.

https://www.electronicspoint.com/threads/repair-help-on-lg-os-5020c-oscilloscope.276494/

https://www.electronicspoint.com/threads/connected-my-oscilloscope-up-backwards.268276/

Exactly the same power supply as mine (as far as I remember since last time I touch it, was 5 years ago):




Voltages on the main board:





As soon as I have the opportunity/time will continue the repair on my unit and update here.









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