Electronics > Repair
Analog oscilloscope ONLY working for a split second when restarted
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osmax_br:
I have a goldstar (LG) 9020g oscilloscope, its problem that it doesn't give any output , so I turn it off and then immediately on and it flashes for a brief second and then no output again :(

I am suspecting the hv circuit is malfunction , the problem is that I have a medical condition call HighVolt-Phobia and I don't know for sure how to test it without getting killed

My question

1- sources on the internet where someone explains how to deal with crt high voltage circuit (I want him still alive just to make sure 😀)

2- do you have any suggestions for the malfunction cause (maybe it is not the hv circuit) ?

3- channels where people fix similar things

4- general advice

5- THX A LOT <3

*There is 2 photos for my little device and the fast flash
tggzzz:
Might be HV, might be the LV PSU, might just need a good internal clean.

Is the fault a new fault?

A 10s gurgle reveals the service manual https://gepengser.weebly.com/uploads/9/6/3/5/9635683/os_9020_g_lg-goldstar_1.pdf
osmax_br:
Yup it is a new fault
Before that it was working but with dim display and then it  stopped working , I don't think it is a crt problem because the crt is flashing on startup
And side note , six months ago it returned working suddenly and I still dont know how it worked , however it worked a few times
I have the service manual , just need to see someone on yt working on similar HV circuit just to know that I am not risking myself

+ All the functions of the oscilloscope are working perfectly fine (function gen , and the xy functions ) and as far as I know they use the same low voltage psu as the crt (maybe I am wrong but that's what I believe )
Thanks for your reply
tggzzz:

--- Quote from: osmax_br on November 04, 2024, 06:44:35 pm ---Yup it is a new fault
Before that it was working but with dim display and then it  stopped working , I don't think it is a crt problem because the crt is flashing on startup
And side note , six months ago it returned working suddenly and I still dont know how it worked , however it worked a few times
I have the service manual , just need to see someone on yt working on similar HV circuit just to know that I am not risking myself

+ All the functions of the oscilloscope are working perfectly fine (function gen , and the xy functions ) and as far as I know they use the same low voltage psu as the crt (maybe I am wrong but that's what I believe )
Thanks for your reply

--- End quote ---

The service manual ought to indicate the "interesting" areas.

Certainly the connections at the other end of the tube could bite, and the other one could be a "sticking plaster" on the side of the next with a thick cable coming from it. The latter takes a long time to discharge.
Analog Kid:

--- Quote from: osmax_br on November 04, 2024, 05:43:26 pm ---[...] the problem is that I have a medical condition call HighVolt-Phobia and I don't know for sure how to test it without getting killed

--- End quote ---

I'll just say that that is a good condition to have. You'll live longer.
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