Tek 2225
 

After putting in a truckload of electrolytics to get rid of ripple in the race I have some residual noise in X 10 mode. I am wondering if it might be almost normal.

In normal the trace is nice and sharp, but in X 10 it is about 0.8 mm. high..

Before the caps it had something akin to a sine wave at double the power supply chopping frequency in all modes, unaffected by the setting of the V/div. It would only go away in add, invert B.

With the case off it does pick up some additional noise, which is gone when you set it to maximum gain, which is when the attenuator is just a piece off wire, and ground reference on the input. At that point you are getting a pretty true picture of how much noise is actually in the system.

I have been tripped up by expecting too much. For example working on an old FM which works but I think no way it is working right because it doesn't get the Akron stations (from Cleveland). I wonder if this is what's going on here.

Tek 2225
 

wrote:


After putting in a truckload of electrolytics to get rid of ripple
in the race I have some residual noise in X 10 mode. I am wondering
if it might be almost normal.

In normal the trace is nice and sharp, but in X 10 it is about 0.8 mm. high.



** Completely normal for a 50MHz scope.

The 1Mmohm impedance and wide bandwidth combine to create about 150uV of noise which makes the trace a bit fuzzy at the high gain setting.



..... Phil

Tek 2225
 

What bothered me was that it was a good piece of one of the small divisions. But then I do remember scopes with a trace about that sharp in normal mode. Well it is "sharp" because it is not unfocussed, it is noisy.

I am just trying to be on the lookout for expecting to much out of things.

Tek 2225
 

Well now it is back. Now, it looks like a little over a mm. with the case on. I cannot think of an explanation for that right now.

I am starting to think there is something wrong with the grounds in this thing - or possibly these things.

I have run the sec/div in auto and uncalibrated, looking for the waveform that was coming from the PS. This really looks like pure noise. We got a spectrum analyser around here somewhere, but then where the hell should I hook it up ? The CRT plates ? Looking at it, that does not look easy but I could definitely find it on the board.

I might just take to using it for a time. The ONLY problem I can see is the 10 X, and I will eventually run that down. Just use the thing and be happy..