HG 5502 scope repair

[pedroteck]

Hello everybody here.

Just found the forum on tapatalk and decided to join in.

Anyways , i have recently got an old scope from a friend .

I decided to check a pwm ic output with it and i accidentally shorted some pins with test probe .

Now i get this on the screen (see bellow)


i checked the probe resistance and its about 400 kohms.

could the problem be related to the probe ? Or worse?

[tautech]

Welcome to the forum.
What waveform does the Cal output on the scope display?

[pedroteck]

Hi and thanks for the quick replay , i must be lucky here .

Is this the one on the picture ?

Also what is the normal probe resistance please ?

[tautech]

Yes.
This Cal output will produce a 1 KHz 1 V peak to peak square wave.
It is used to calibrate a 10x probe only.
The trimmer of the probe compensation is to be adjusted for a perfectly shaped square wave display.
So adjust the vertical attenuation for close to a full vertical display and timebase for ~2 div period (0.5 mS (500 uS)) and adjust the probe trimmer.
So a 200 mV/ div setting should display 5 div high for 1x probe and 20 mV/div setting will display 5 div for 10x probe.

Understand all this and it will indicate if your probes are OK.

[pedroteck]

Ok man.

I have assembled the scope , i will check the cal signal and be back with news.

[pedroteck]

Hi i have checked the 1v cal output and it actually showed up on the screen .

I dont how it happened because before desassembling the scope i could not display anything.

Thanks for the time man .