I got my scope working fairly well, but I have a question.

With no input signal, as the "time/centimeter" is set lower and lower, to 0,1us, the line becomes fainter
and fainter, on both A and B channels, CA plugin used. It also occurs when fed the calibrated signal as
well. It occurs whether the triggering mode is "auto" or one of the other functions.

I did have a problem with the line going completely black, just a bright dot at 0,1uf, but installed new
tubes which seems to have alleviated the problem, at least somewhat. And that is my question, should the
line be going darker at all as I go to 0,1us?

I have checked the supply voltages and all are within 1%. I set the 'A'triggering level, and 'A' Internal Trigger DC Level'
so you know what I have done so far.

That line going darker has me a touch worried.

Thanks for any help and time.

pos

 

When you say the trace goes darker I assume you mean the trace goes more dim, i.e. less bright.
This is normal because the trace is spending less time on the screen.

Also, it depends on the repetition rate of the input signal being viewed.
Apply a signal from a function generator to get a better assessment of the level of brightness.

Finally, CRTs get weak with age. As the CRT gets older the brightness diminishes just like most of us humans.

 

as the "time/centimeter" is set lower and lower

By that do you mean a faster and faster sweep speed (smaller time/cm)?
If so, that's normal for a CRT oscilloscope.

 

Slight dimming is normal but if the dimming is considerable then read on.

There is a property called trigger 'hold-off' to allow the trace to flyback to the start position at the left of the screen. If the hold off is too large this will make the trace dimmer. I don't think this 'scope has a hold off control but, instead has a stability control. Try adjusting this - probably fully counter-clockwise.

Otherwise there may be a fault with the circuitry which controls the trigger hold off.

 

Thanks Gents. I just found out that when I switched all the tubes around on the "door", I switched a 12au6 tube with a 6au6 tube.
V261 is what caused the B channel problem. Yes, the line dims a little as I switch to 0,1us, but it works.

All is ok now.

Solved, fixed.

Thanks for time and efforts Gents.

pos

 

Does the oscilloscope show traces at slower settings?
If you see traces then the problem could be in the triggering setting.
Try adjusting the trigger controls.