hello, i have this oscilloscope that looks haunted Almost always there is no signal on the screen. Sometimes, if you increase the intensity of the track, you will notice that the track goes off screen. Sometimes you only see a fixed dot on the screen if you apply a signal instead it becomes a vertical line but does not scroll regardless of the position of the tempo selector knob. At best, when you apply the signal for calibration you see these bows last pic. sometimes the screen just doesn't show anything. after a while it starts working again.

I know that this info is insufficient to be able to make a diagnosis. From experience, someone has had similar problems in the past. Do you think the problem could be the potentiometers on the front panel? I have tried using deoxidizer spray with no success.

 

That looks like the Sweep time base setting, have you got it set to delay mode instead of instant?

 

there's no difference ...
I have an other Philips pm3212 25MHz and sometime I got the same problem

 

It's likely bad switches, connectors or anything with a electrical contact. Deoxidizer with a needle works on switches better than spray, For connectors physical reconnection usually wipes the electrical contacts if you can also get a bit of Deoxit in there.
https://caig.com/product/deoxit-d100l-25c/


A long plastic insulated pusher rod can help to isolated bad connections. Push slightly on each part until you see some change on the device, turn-off, condition that part, reconnect, power up ... rinse, repeat on the next flaky connection.

 

This photo tells me that you have a working oscilloscope.

So what is the problem with it?

 

in this photo The probe is connected on the CAL terminal from the other oscilloscope ( Philips pm3212 ) 1.2v square wave i don't remember the freq. Do you think I can accept it like a square wave? All the rest of the photo are made in less than 10 min. so it's not working well.

 

in this photo The probe is connected on the CAL terminal from the other oscilloscope ( Philips pm3212 ) 1.2v square wave i don't remember the freq. Do you think I can accept it like a square wave? All the rest of the photo are made in less than 10 min. so it's not working well.

Switch the CH1 to DC and check the probe compensation.
https://www.rohde-schwarz.com/us/pr.../understanding-probe-compensation_254520.html