Old HC 5502 analog scope ( some display problems )

[cowboybob]

Its exactly what i see a moving dot with slow frequency ....

That's just the "persistence" of the CRT.

https://en.wikipedia.org/wiki/Cathode_ray_tube#Phosphor_persistence

As the electron beam passes over the face of the CRT the resultant glow only lasts for a short time (milliseconds). Thus all you will see is the dot as it travels left to right at the slower sweep speeds.

...i will try with higher frequency and see how this looks .

Once the sweep is triggered it will only traverse the scope face at the speed you have selected. A 0.5/sec sweep will, in your case, always just be a dot leisurely going across the CRT. Increased input signal frequecy will result in an actual trace for vertical transistions but the horizontal trace will remain a mere traveling dot.

And a CRT persistence duration degrades with use. Since you have a "legacy" device, the reduced persistence is more pronounced (and it tends to smear, or broaden). The "flicker" you are seing with AC is also an artifact of the persistence issue.

 

[BGAmodz]

So this is mainly due to an old Phosphor-coated inner side of the screen , is there a way to make it fresh again ?

 

[KeepItSimpleStupid]

Even fresh, it won't do what a DSO (Digital Storage Oscilloscope) would do. But, an ounce of prevention is worth a pound of cure. Use the minimum trace brightness to avoid burning the screen.

 

[BGAmodz]

Even fresh, it won't do what a DSO (Digital Storage Oscilloscope) would do. But, an ounce of prevention is worth a pound of cure. Use the minimum trace brightness to avoid burning the screen.

I see a nice looking graph on the picture on post 22 , its really worth it if i can get similar results , i just need to know how i can get the phosphor coating of the screen done .

 

[KeepItSimpleStupid]

If you use the calibrate tab on the front of your scope for the signal, it should look like you expect.

 

[BGAmodz]

If you use the calibrate tab on the front of your scope for the signal, it should look like you expect.

I see that the only way to get around this is eather change the CRT with a fresh one witch i don't think its going to be an easy find or figure out a way to improve the phosphor coating .

The reason i want to fix this is to display signals with tiny details like this one :

 

[mab2]

I see a nice looking graph on the picture on post 22 , its really worth it if i can get similar results , i just need to know how i can get the phosphor coating of the screen done .

I expect the waveform on post #22 is at a much higher frequency than 0.5Hz. even with a new crt I doubt your scope would show a trace like that at 0.5Hz.

If you really want to see waveforms at that frequency you need a storage scope - I did see once a free downloadable 'oscilloscope' program that would digitise the mic input of a PC and display it as a waveform - that would work OK at 0.5Hz; or there are lots of cheap DSO adaptors for computers on ebay which would do it even better.

The reason i want to fix this is to display signals with tiny details like this one :

you should be able to see details like those on your scope as it is - if the intensity isn't too high and the focus/astigmatism are set right.

 

[cowboybob]

I see that the only way to get around this is eather change the CRT with a fresh one witch i don't think its going to be an easy find or figure out a way to improve the phosphor coating ....

New CRT only option. And, yes, not easy or cheap.

...The reason i want to fix this is to display signals with tiny details like this one :...

As noted above, you can probably do that with what you have.

Play some more ( a lot more) with the scope, trying different sigs, scope settings (especially sweep speed, brightness and focus) and ambient lighting scenarios. I suspect you can get what you want eventually. You've got yourself a very nice, if dated, scope.

Little DSOs are cheap, have a lot of functions for the price and are portable, but I wish I still had my old Tektronix CRT type. Some nostalgia, sure, but I miss the much bigger screen and real knobs, ALL easily accessible and with a lot less cluttered screen .

 

[KeepItSimpleStupid]

CBB:

You really can't turn a CRO into a DSO.

You can only fix burnt phosphors, by replacing the tube.

 

[cowboybob]

CBB:
...You can only fix burnt phosphors, by replacing the tube.

New CRT only option. And, yes, not easy or cheap.

...You really can't turn a CRO into a DSO. ...

KISS, my friend, you are, of course correct, but I don't know how you got that interpretation from my post.

 

[KeepItSimpleStupid]

The OP wants DSO like performance from a non-storage CRO.

 

[cowboybob]

I see what you're saying.

Thanks, KISS.

 

[BGAmodz]

Hello again , i guess its time to get this topic from the tombs again And i think now a really got some display problems

Any ways i was checking a power supply ( ON ) PWM IC with the prob on output pin and suddenly a small spark came out of that pin , am sure i shorted its pins somhow with the probe's head .

Now the scopes horizontal line has become leaning downward from the side , and stays like that even if you do a voltage test , and the same with channel 2 .

Can this be related to the circuitry near the probe's input ?? or is it something bad ?

 

[JimB]

Somewhere, probably on the back panel of the scope there will be a "Trace Rotate" control.
Try turning that to level the trace to the graticule.

JimB

 

[BGAmodz]

Somewhere, probably on the back panel of the scope there will be a "Trace Rotate" control.
Try turning that to level the trace to the graticule.

JimB

Hi JimB

Unfortunately that didn't solve it , the trace turns but i get no voltage reading , at least the CRT is showing the trace witch is good .

 

[dr pepper]

Sounds like you messed something up in the deflection circuit, probably after the attenuators, possibly a fet.
Do you have the schems?

 

[KeepItSimpleStupid]

If both CH1 and CH2 are affected, I'd be looking at the power supply and/or horizontal sweep. Trace rotation is more like a "tilt" control. CRT TV's did it with magnets on the neck.

 

[dr pepper]

My philips 'scope had a real fancy magnetic coil arrangement on the back of the tibe just for trace rotation.
I couldnt see this being affected, unless as kss just mentioned the power supply has been damaged, that is more likely if the 'scope ground has been connected to a voltage source with one side connected to ground

 

[BGAmodz]

Thanks to all of you above , i will do some checking and let you know

Sounds like you messed something up in the deflection circuit, probably after the attenuators, possibly a fet.
Do you have the schems?

https://i.imgur.com/YvOCIlY.jpg

 

[dr pepper]

That looks like the beam control circuit and the eht, the fault is more likely to be in the power supply schem, or the y amp/attenuator.
A fault on the schem you posted would either be a blank screen or a dim/unfocussed dot.