Need help evaluating my oscilloscope! (And sincere greetings to all!)

Thread Starter

Mikuda

Joined Mar 23, 2017
10
Hello! In short as title says. I wasn't sure about forum section so I posted here.
I'm just starting to learn electronics and scope operation so please be understanding :)
I've purchased used Tektronix 2445A oscilloscope and I'm not sure about it's condition. After running tests from "Checks and Adjustments" in manual It seems to work properly except for some glitches I wanted to sort out - whether they are normal OR I'm doing something wrong OR are they signs of imminent failure/death of a scope. It was sold as refurbished/calibrated with 90 days warranty and 14 days return policy so I don't have to worry if it turns out to be crap :) I can send it back ASAP - just need Your judgement.
It's my first analog scope (never used nor seen one up close in operation before) so my concerns may be simply result of lack of reference.

So, my concerns:
1. I already have HP54600B which is digital CRT so first big difference is display sharpness. I can set focus on Tektronix to obtain sharpness but it's not as sharp as HP. Is it normal and typical on analog scopes vs early digital and I just have to get used to it?
2. Each time I push menu buttons or rotate volts/div sec/div knobs most indicator LEDs blink for a fraction of a second. Is it normal?
3. When using calibrator, I can't obtain nice square wave using AUTO setup, it sets to 200mV - 20ns. I can do it manually though. Should I be worried about it? Funny thing is, when I cross-connect Tektronix and HP calibrators, they auto-detect and display each other just perfect.

I can post some photos or short video to demonstrate those if necessary.

Please let me know what You think! Do I own well-preserved piece of equipment or should I get rid of it while I can?
Thanks in advance!
 

RichardO

Joined May 4, 2013
2,268
1) Can you post a picture of a sine or triangle wave when the scope is focused the best you can get? (Enable bandwidth limit so noise won't show).
2) I have not used scopes of this series except in passing but the flashing LED's does not sound right to me.
3) I don't know anything about AUTO setup, sorry.
 

RichardO

Joined May 4, 2013
2,268
The focus looks good to me. Even the alpha-numerics look sharp.

I see that flicker of the LED's that you are talking about. I am not sure if that is normal or not.

I have mixed thoughts on this. Every time I have used a Tek 2465 I was very frustrated by the extremely slow response to the front panel controls. So slow that the settings changes could not keep up with my slow reflexes. For instance if I pressed the AC/DC/Ground button twice quickly the scope would only react to one of the presses. Horrible.

On the other hand I don't remember ever seeing the LED's flicker. This may have been because I was so intent on watching just the LED's of the mode I was changing to make sure they did what I wanted.

Hopefully someone else on this forum has more experience on the flickering question.


p.s. I believe that the slow update rate of the LED's from the controls is because these are read and written using shift registers driven from a Motorola MC6802 microprocessor. This allowed the easy distribution of the on/off data throughout the scope without causing a lot of digital noise.
 

recklessrog

Joined May 23, 2013
985
I've still got one of these although I have not used it for a while.Your focus looks ok although should improve if you turn the brightness down a bit. As far as the flickering leds are concerned, I don't remember that, and as long as it works ok I would not be too worried. It could be that there is a loose connection somewhere that gets jolted when the switches are pressed, but I cant recall whether it is normal. As mine is buried amongnst a ton of stuff in my shed it's not going to be possible to drag it out and test anytime soon
 

Thread Starter

Mikuda

Joined Mar 23, 2017
10
Thank You both for replies! I think I'll keep it after all. As for focus I concur with your thoughts, it's just difference between two display methods used in fully analog and semi-digital scopes. I hope someone with not-buried scope will shed some more light on those flickers :)

One more question - there are ground sockets near calibration wave sources but obviously they cant be grabbed with ground clamps attached to probes. What kind of connectors are they? How do I properly connect probe ground lead there?
 
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