I picked up two Leader LBO-32B Oscilloscopes at a estate sale. One powers up but the screen is blank, so it’s good for parts. The other powers up and I get the wave pattern but after about two minutes the wave fades away. The interesting thing is that when I turn it off, a small bright dot slides back on the screen.



I was hoping someone can give me some direction as to what to look for. I'm planing on pulling some parts from one to get the other to work.



Any help would be appreciated.

 

Does the wave "fade away" as in "intensity becomes lower and lower" or does it drift out of view in a particular direction? The dot in the center of the screen when the unit is turned off is the result of the cathode in the CRT (cathode ray tube) still emitting electrons from residual heat and the high voltage still hasn't dissipated from the tube. Since the deflection circuits have lost power, the beam simply goes straight out to the center of the screen.

 

Yes the intensity becomes lower and lower I can adjust the intensity up, but after the intensity is turned all the way up it just fades away.

 

Since this unit is from the 1960's, one of the first things that needs to be done is to replace all the electrolytic caps. Age is not kind to these particular components.

 

Already started making a list, I also tried fine tuner spray on all the controls and swapping the tubes from one unit to the other. Anything else I can do while I wait for the parts to come in?

 

I spent a little time (not a lot) trying to find a schematic on-line. I didn't have any luck, but again, didn't spend a lot of time. You may have better luck. Leaky capacitors can do all kinds of strange things so I'm hopeful that replacing yours will do the trick. Remember, some are axial and some are radial. It may be easy to overlook the axial types if they are going, as an example, from a switch to the boards.

 

Bill,
Thanks for trying, I too did not have much luck finding anything on this unit. Best I came up with is a service manual for a 70's unit which said the power supply circuit should be checked. So I'm starting to check that now.

Again Thanks For Trying
Phil

 

Not meaning to hijack the thread but I was also looking for some parts for a Leader LBO-522 20Mhz oscilloscope. Someone had twisted off some of the knobs. Looking for replacement pots at the component level.
Anyone know where I may find some parts or parts dealers for Leader?