IWATSU oscilloscope Cal signal square wave showing as ramped / curved signal

[Michelle]

You’re right, next time I should fully explain what I’ve done, am trying to do, and all relevant information. For now I’m going to clean the contacts because I didn’t realize that might have been an issue specifically the v/div knob affecting the waveform display... I did try ch2 with the same result and I do understand the capacitance adjustment range and ordered a $20 probe master from eBay that should work.

Thanks for the help. I think cleaning and the new probe will get it back in order.

[tggzzz]

You’re right, next time I should fully explain what I’ve done, am trying to do, and all relevant information. For now I’m going to clean the contacts because I didn’t realize that might have been an issue specifically the v/div knob affecting the waveform display... I did try ch2 with the same result and I do understand the capacitance adjustment range and ordered a $20 probe master from eBay that should work.

Thanks for the help. I think cleaning and the new probe will get it back in order.

You're welcome.

Cleaning often works unexpected wonders, but with some 60s/70s/80s Tek scopes you have to be careful of the mechanical switch construction and only use IPA to clean.

The other traditional problems are dried-out electrolytics, and the (most "entertaining") RIFA capacitors.

[bdunham7]

I did try ch2 with the same result

That's interesting.  The input circuitry, including the circuitry and attenuator switches actuated by those V/Div knobs, are not shared between channels.  Seeing the problem on both channels more or less rules out a lot of things. 

[edpalmer42]

I did try ch2 with the same result

That's interesting.  The input circuitry, including the circuitry and attenuator switches actuated by those V/Div knobs, are not shared between channels.  Seeing the problem on both channels more or less rules out a lot of things.

Not necessarily.  Both switches have been in the same environment.  If they've been sitting around unused for years, it wouldn't surprise me to find that both of them are similarly oxidized.  Actually, just spinning the switches back and forth a few times might be all that's required to cut through the oxide layer.

Michelle, another reason to always start with the basics is that lots of beginners read these messages.  When I answer a question I often 'play to the audience' rather than just the OP.  Besides, although I'm an electrical engineer, I don't know shit about automation engineering so if you ever answer a question from me I hope you'll use words of one syllable or less!  We're all beginners!   

Ed

[Michelle]

I did try ch2 with the same result

That's interesting.  The input circuitry, including the circuitry and attenuator switches actuated by those V/Div knobs, are not shared between channels.  Seeing the problem on both channels more or less rules out a lot of things.

Yeah I’m not totally sure what to make of it, based on the fact that I got a square wave from the bare wire on ch1 after turning the knob I figured the most logical next step would be to get an appropriate probe then see what happens on both of the channels. I didn’t try the bare wire on ch2 though, I just tried tuning the lecroy probe on it like I did on ch1. But now that the bare wire somehow went from the swept signal to the square wave I’m going to try both my lecroy and Agilent probe tomorrow just to see what happens.

Another theory I had was that it could have something to do with it having warmed up for longer, even though the other day I left it on for a couple hours before even trying the probe, and it was only on for about a half hour today before I tried the bare wire.

It could be that it was just chance that turning the knob wore through oxidation.

[Michelle]

I did try ch2 with the same result

That's interesting.  The input circuitry, including the circuitry and attenuator switches actuated by those V/Div knobs, are not shared between channels.  Seeing the problem on both channels more or less rules out a lot of things.

Not necessarily.  Both switches have been in the same environment.  If they've been sitting around unused for years, it wouldn't surprise me to find that both of them are similarly oxidized.  Actually, just spinning the switches back and forth a few times might be all that's required to cut through the oxide layer.

Michelle, another reason to always start with the basics is that lots of beginners read these messages.  When I answer a question I often 'play to the audience' rather than just the OP.  Besides, although I'm an electrical engineer, I don't know shit about automation engineering so if you ever answer a question from me I hope you'll use words of one syllable or less!  We're all beginners!   

Ed

You’re right it probably makes just as much sense to assume someone didn’t do something basic as it does to assume they did. Either way I realize I need to provide more information at least on a forum like this where people can actually understand what you’re saying.

Sorry for having an attitude earlier I needed to eat lunch lol.