Leader LBO-315 oscilloscope problem

[hyrava]

I got Leader LBO-315 oscilloscope for free few days ago. Both channels seems to work, I can see traces and both channels react to signal.

Problem is that every about 15-20 seconds power led turns off, screen goes blank and I can hear snapping sound somewhere inside. I haven't repaired any scopes before but I think problem is maybe in power supply (or high voltage arcing).

I opened it and nothing looks visually burned, exploded or overheated. Does anybody have service manual or schematics to that scope? I tried to google but didn't find them.

I apologise my bad English, I live in Finland and English is my third language.

[wattsjake]

Try turning on the oscilloscope with the cover off. You'll be fine as long as you don't touch the CRT or anything inside of the oscilloscope. Try and verify where the pop is coming from.

Are there any other issues that the oscilloscope has? What happens on the screen when it pops? I'll try and look for schematics for it. Do you have any other information about the oscilloscope. Name, serial number, manufacturer, date of manufacture.

[cvanc]

Carefully run it with the covers off in a dark room - can you see a place where it is sparking?

[hyrava]

Okay, today morning I had some time to take off top and bottom covers. I put scope on its side so I could see both sides. I turned it on and everything was fine (power-led on, both traces visible, no strange noises...) until... After about one or two minutes I heard first snap. Snapping interval got shorter and shorter until it sounds like intermittent buzzer. And then I saw where it is sparking. It is sparking between CRT and two springs (see attached pic, red circle). What does this mean?

When sparking, power led turns off and screen goes blank.

As i mentioned in 1st post, manufacturer is Leader Electronics Corp. Japan, model LBO-315, serial 6010129. I don't know manufacturing date but it is last serviced by FinnMetric Oy in 30.6.1989.