need help fixing a Leader scope

The screen on my 25 year old Leader LBO-508A went blank yesterday. I?m regularly fix electronics, so I opened up the case to check it out. Not being used to work on scopes (or HV TV equipment) it looks like I?ll need at least the schematics to measure it out. And now I don?t have a scope to do this anymore!

- Does anyone happen to have the schematics of the Leader LBO-508A or know where to get them? A google search got me 1 good link but the email came back :(

- Any suggestions on where I should start to find the problem? All the heatsinks in the High voltage and final amp are getting still warm. But no picture on the tube. Anyway to make sure the tube is still good and getting power?

- Could I bring the video signal outside and hook it to some other display?

I appreciate all the help I can get.



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You might save yourself a lot of time by checking the heater first. If that's gone the tube is scrap.


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Pooh Bear


Thanks, Turned out I was lucky and I found very small numbers on the trace side of the PCBs. This way I eliminated some areas to have problems and ended up in the HV power supply. Everything was there except for the

-2000V. From the parts and traces I understood it was a regular voltage doubler. Found the 1st cap (1600V .5uf) to be "open", replaced it and my scope is up and running again. :) Took about an hr or 2, well worth it.

Thanks for the suggestions

Stefan V

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