Leader LBO-524L Oscilloscope (or similar advise for any generic 1980's Jap Scope

[squibby]

I have a Leader LBO-524L in good condition for age, and downloaded some manuals off the web inclusive of wiring diagrams.

Now I'm well versed in repairing Valve tube stuff, but anything with transistors is new to me, and scopes are new to me so i don't know where to start.

Normally I would just use it, but it seems to have a fault that is symptomatic that not all is well on the inside. It's a 35Mhz Scope, but it loses the trace at about 900KHz on either channel. And what I mean by this is the perfect sine wave just disappears from the CRT, no dot, no lines, nothing and I can't find it again until I wind the frequency back down whereby the perfect trace appears again.

 (I checked my signal generator with another scope, so I know it's the leader scope at fault and not the source equipment).

Otherwise, seems to work great delivering the correct frequency and voltage for my sine wave, only, disappearing at about 900KHz instead of 35Mhz. Does anyone know what that kind of fault is a symptom of with a mid 80's japanese scope? Where do I start?

I want to start with the easiest most likely faults finding first, and then move on from there.

[squibby]

It’s quite pleasing on the eye. I would enjoy extending its life a bit more.

[wasedadoc]

To the right of the power button is the trigger level knob. If it is currently pulled out, push it in and try again.

[squibby]

Oh. That’s kind of embarrassing. It can read 1MHz now and that’s all this generator can go up to, but it’s gone past where it stopped last time. Maybe I need to learn how to use it before I open it up lol. Thanks so much for your post.

[BlownUpCapacitor]

It also looks like you've been triggering externally. Unsure if you are purposefully doing that, but but the switch to source the trigger from channel 1. You also have have it set to trigger on TV signals. Maybe you do a lot of television troubleshooting?

[TimFox]

When you encounter difficulties with triggering, you should go to the “auto” mode on trigger, which will always produce a horizontal sweep.
Then, you can play with the vertical controls to find the waveform.

[squibby]

I had a play with it yesterday. I have an ancient tek that's 33Mhz but the dual trace plug in on it is 22Mhz. And unfortunately the only thing I got to test those kind of frequencies currently is a 60 years old tube driven osicllator (also a leader actually)  .

But anyway, the Leader scope and the Tek scope were both losing the trace at about 22Mhz. So in theory the I should have been able to see higher frequency with the Leader, so I'm a bit sus whether it's the oscillator or the scopes, but, 22Mhz is close enough to 35Mhz that I am happy enough with that. Also, I have my doubts with the old valve tube oscillator, the waveform is nowhere near as pretty as a newer signal generator and that's probably making life hard for me and the scopes also.

So anyway, yeah, I think I got this now, and once i get to try it on a better signal generator, maybe the results will be even closer to the specs on the scope.