Help with old oscilloscope

[Divarin]

This might not be the best forum for this question but I'm throwing it out anyway.

 

I picked up an older oscilloscope, a Hickok model 517 dual trace 15mhz oscilloscope. 

 

First I'd like to start with the disclaimer that I know next to nothing about oscilloscopes, never owned one never used one, never been around anyone using one.

 

It didn't have a probe so I ordered a pair of probes off Amazon https://www.amazon.com/gp/aw/d/B0030KWM30?psc=1&ref=ppx_pop_mob_b_asin_title

 

I looked for "15mhz probes" but couldn't find any so I took a chance that these would work as well.

 

I'm not able to see a square wave when I stick the probe into the calibration "hole" and I'm not really able to make sense out of anything. As a test I tried just probing a 9volt dc power supply with it set up to 1 volt per cm thinking ... okay if it's working I expect the horizontal line to jump up 9 divisions.  It didn't. If I set it to 0.5 volts per cm then the 9 volt power causes it to raise about 1.5 divisions (cm's)

 

Before I give up on this scope can someone let me know if I'm going about this wrong using the wrong probe and if so where I might find a correct probe for this scope or is it more likely that the scope is not working properly? 

 

Let me know if there's specific tests I should run to give more useful information.

 

Thanks in advance. 

[+batari]

4 hours ago, Divarin said:

This might not be the best forum for this question but I'm throwing it out anyway.

 

I picked up an older oscilloscope, a Hickok model 517 dual trace 15mhz oscilloscope. 

 

First I'd like to start with the disclaimer that I know next to nothing about oscilloscopes, never owned one never used one, never been around anyone using one.

 

It didn't have a probe so I ordered a pair of probes off Amazon https://www.amazon.com/gp/aw/d/B0030KWM30?psc=1&ref=ppx_pop_mob_b_asin_title

 

I looked for "15mhz probes" but couldn't find any so I took a chance that these would work as well.

 

I'm not able to see a square wave when I stick the probe into the calibration "hole" and I'm not really able to make sense out of anything. As a test I tried just probing a 9volt dc power supply with it set up to 1 volt per cm thinking ... okay if it's working I expect the horizontal line to jump up 9 divisions.  It didn't. If I set it to 0.5 volts per cm then the 9 volt power causes it to raise about 1.5 divisions (cm's)

 

Before I give up on this scope can someone let me know if I'm going about this wrong using the wrong probe and if so where I might find a correct probe for this scope or is it more likely that the scope is not working properly? 

 

Let me know if there's specific tests I should run to give more useful information.

 

Thanks in advance. 

Did you get X10 probes? Those reduce the amplitide by a factor of 10, so your results sound (somewhat) normal. If you want the full amplitude, get X1 probes, or use those and remember that they are X10.

[Divarin]

it's switchable between 1x and 10x. oh now that I think about it I tried to calibrate with it on 10x but didn't switch it back to 1x when measuring the 9 volt power supply.  I'll try that. I wonder if I was supposed to calibrate on 1x as well, the manual that came with the probe says to calibrate on 10x but then again that might be assuming a different type of scope.

[+-^CrossBow^-]

Yes...you really only use the 10x selector on your probes when you are needing to measure something that is higher voltage than what you can read on the scope. The 15mhz isn't related to the probes themselves. So yes you pretty much use a scope for smaller electronics with the probes in 1x mode most of the time. On your calibration, some scope requires that all the dials be in a certain position to know that everything is properly calibrated? On mine I set it to .5v per division because my CAL actual reads with only .5v PP on it. I think on the time division I use whatever around the .1 timescale that gives me a few nice easy to see square waves on the screen. Also scopes usually have trimmers outside and some inside that are also used to properly calibrate the scope beyond just the CAL check itself. However, you should not mess with those calibration trimmers unless you have clear documentation on the proper procedure to do this! Or better yet, if you really want to spend the money, send it to a calibration company specifically designed for this. Mine only has a few on the sides to adjust with about a half dozen more internally. I know mine is out of CAL in a few settings but it could be the control knobs just being flaky etc but for what I've needed and used it for mine has been great to use! I did look at and get a quote on calibrating my old scope. But it was quite expensive honestly and for the price being asked for, I could literally buy one of the Rigol digitals that has more features and would be brand new. So I passed on that for the time being.

 

 

[+Stephen Moss]

On 8/22/2020 at 6:24 PM, batari said:

I'm not able to see a square wave when I stick the probe into the calibration "hole" and I'm not really able to make sense out of anything. As a test I tried just probing a 9volt dc power supply with it set up to 1 volt per cm thinking ... okay if it's working I expect the horizontal line to jump up 9 divisions.  It didn't. If I set it to 0.5 volts per cm then the 9 volt power causes it to raise about 1.5 divisions (cm's)

If you probe was set to x10 then that would give a measurement of about 7.5V @ 0.5V/Div so not to far off but how certain are you that your 9V source was actually 9V to start with by verifying it with a multi-meter first? If it is 9V, it is possible you may be dropping a little due to dirty switch contacts, always good with old mechanical switches to give the blast of switch/contact cleaner occasionally if you can access them. 

 

As for not seeing the square wave it may not be outputting any signal, you may not have been making good contact or they may be a on/off button for it somewhere.  

[Divarin]

Well setting the probe back to 1x definitely seems to have helped. I still can't get the calibration to work but I was able to read the 9volt power supply as expected.  Also I tried turning the calibration control on the probe while connected to the 9volts and it didn't seem to do anything.  When I get more free time I'll start poking around some chips and see if I can make out actual signals.

 

In the attached images there are "Cal" (with an arrow) labels marked next to the volts/time per cm knobs but the black time knob doesn't turn that far and neither do either of the reds (in-fact the reds don't really move much at all so maybe that's the issue).  The signal is the closest thing I can get to a square wave while the probe is put into the calibration port.

 

 

Edited August 24, 2020 by Divarin

[+DrVenkman]

8 hours ago, Divarin said:

Also I tried turning the calibration control on the probe while connected to the 9volts and it didn't seem to do anything. 

The calibration of a scope needs to be done with a known, fixed signal, not a steady voltage. The calibration point on a modern scope is a little clip you connect the probe to that typically generates something like a steady 1KHz square wave - you get that signal on the scope display, then adjust the probe calibration until you eliminate any over or under shoot on the rising edge of the signal. 

 

So you have a new probe, correct? Remove the pull-off clip on the end and expose the point contact and insert into the calibration port. Based on the signal you show above, try to decrease the V/division setting on the scope to make each pulse "taller." Then decrease the time/division as well to stretch out the traces so you have a bit more precision available for each pulse. On an older CRT like this one, especially one whose electronics and CRT are of uncertain age, a properly calibrated probe will give something that is likely to look a lot like a series of alternating dashes, above and below the center. The rises and falls on a square wave should be instant and an older CRT won't necessarily give you enough persistence to see much if any of those rises and falls for a properly calibrated probe.

 

 

[+Stephen Moss]

On 8/24/2020 at 2:51 PM, Divarin said:

In the attached images there are "Cal" (with an arrow) labels marked next to the volts/time per cm knobs but the black time knob doesn't turn that far and neither do either of the reds (in-fact the reds don't really move much at all so maybe that's the issue).  The signal is the closest thing I can get to a square wave while the probe is put into the calibration port.

The red "variable" knobs allows you to adjust the seconds/volts per division away from the "calibrated" value set by the black dial. Personally I have never understood why you would want to do that as once adjusted away from the calibrated value any measurement will be in accurate as you no longer know what the seconds/volts per division are. 

The only time it makes sense to adjust away from the calibrated value is if your graticule has 10% & 90% markings on it (yours does not), as then you use the variable to adjust the square wave amplitude to 100% relative to the 10% & 90% marking and can then measure the rise time between the 10 and 90% markings.

 

If your scope follows tradition the red knobs should be turned as far as the will go to the right, once there they are in the "Calibrated" position and the seconds/volts per division should match those set by the black dial. Generally, when in the "Calibrated" position indicator on the red knob would be horizontal and on the right. I really hated scope that had that feature at work as the hamfisted undergrads students would fiddle with it and keep trying to turn it beyond the (usually indented) stop, sometimes breaking the stop so that it just went around and around but nearly always altering the position of the knob on the shaft so the the pointer on the knob did not line up the the indicated Calibrated position when it was set to the correct position. 

Try gently turning the Red knob the the left and then back to the right until it stops, when it comes to a stop while turning to the right it should be in the calibrated position, if the line position indicator on the knob is not horizontal (or in your preferred position) then the knob may have turned on the shaft, you will need a small Allen (Hex) key to loosen the grub screw so you can rotate the knob to the correct position.

On 8/24/2020 at 2:51 PM, Divarin said:

Also I tried turning the calibration control on the probe while connected to the 9volts and it didn't seem to do anything.

The adjustments on the Probe are usually only for when it is used in the x10 position, you may notice that when displaying a with a square wave with the probe in its x10 setting the the corners are either rounded or have under/over shoot (extends beyond the top/bottom edges of the waveform). If necessary, you use the adjustment on the probe to make adjustment until the corners of the square wave look square (90 degrees). However, once performed such an adjustment is only guaranteed to be correct when that probe is match with that specific channel on that specific scope, as the input impedance and capacitance of other channels may vary slightly.

That bottom image in your last post looks to me like a square wave connected via a badly adjusted probe set on x10 or the input is set to AC coupling instead of DC.