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Electronics => Repair => Topic started by: frankX0 on April 29, 2021, 08:19:09 pm

Title: CRT oscilloscope issue
Post by: frankX0 on April 29, 2021, 08:19:09 pm

I have a Leader LBO-310A oscilloscope which was working fine until recently.
It now produces "extra" lines which go from the actual beam position on the screen to a point in the middle of the CRT. Both X- and Y-channels work properly,
The photos show the scope in XY-mode, where I can freely move the position of the actual measurement, but with the addition of the extra lines.
I have the service manual with the schematics, which does not look over complicated. But I also cannot deduct which part is causing this failure.
Help is appreciated!

Title: Re: CRT oscilloscope issue
Post by: David Hess on April 29, 2021, 11:13:10 pm

That looks a lot like ripple on the supply voltages because the aluminum electrolytic capacitors have worn out.

Title: Re: CRT oscilloscope issue
Post by: bob91343 on April 29, 2021, 11:13:35 pm

Bad CRT maybe.

Title: Re: CRT oscilloscope issue
Post by: frankX0 on May 01, 2021, 05:40:00 pm

I would not call this DC (see attachment). Nor would I call this ripple btw.
The 47uF/315V elco's are gone.
Thanks for pointing me in the right direction!