# Need Advice on First Scope - Tek 2246

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#### DustinB

Well shipping is $41. It only comes with 1 - 1x tek probe. I take it I will need a 10x as well? Last edited: #### rfs100 ##### New Member a 10x will be handy, but they can be found used fairly inexpesively. #### DustinB ##### New Member Thanks, I think I'm going to go for it.$225+\$41 shipping and he said he will include 3 probes for me. 1 - 1x, 1 - 10x, and 1 - Switchable 1x-10x.

I just don't know how long it's been since it was calibrated or how much of a difference that might make.

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#### rfs100

##### New Member
even a crappy 2246 is better than a lot of brand new scopes available today, although most of the newer ones will be smalller and lighter in weight. I dont use mine as much as I used to. I had to carry mine from customer to customer, lugging it in and out of my trunk, banging it around mercifully...but it still works as well as it did when I bought it. Im fairy certain that Im going to be buried with mine.

#### DustinB

##### New Member
Does the trace look ok to you in the picture? Looks a little strange compared to what I've seen.

#### DustinB

##### New Member
Well I went ahead and bought the scope, it should here here monday.

Are there any basic tests I can run to verify it's working properly? As it stands I know nothing about oscilloscopes. I think I have 3 days to notify for return if there is a problem.

##### Well-Known Member
I think you will be happy with it. As to this comment:

Does the trace look ok to you in the picture? Looks a little strange compared to what I've seen.

I saw one image with a square wave where the leading and trailing edges may have had some minor under compensation but not a big deal.

Are there any basic tests I can run to verify it's working properly? As it stands I know nothing about oscilloscopes. I think I have 3 days to notify for return if there is a problem.

Start by getting familiar with the scope and what it does. There should be a cal out on the front panel. That will give you generally a 1 KHz square wave to visually look at. Get familiar with your scope probes it comes with and probe compensation adjustments. Going from no scope to a scope that is though not real complex it does have features you need to learn and understand. If you have anything that will give you some known signals, look at them. Again, take your time and get a handle on what the instrument is doing. Google can be a friend, Google O Scope Tutorials and similar phrases.

A word to the wise. Do not immediately try doing things like looking at the 120 VAC wall outlets. I believe on your new scope that the shield common of the vertical input channels is common to all channels and ground. If your ground lead from a probe or those outer BNC connector shields hits the hot side of the AC mains, bad things will happen. Again, start slow, measure low voltages and get friendly with the scope. The scope is a tool and a great tool.

Got a DC power supply? Learn to use DC coupling and measure some DC low voltages and watch the trace shift. Then AC couple and turn the vertical gain up and look for AC ripple on the DC level. Something you won't see with a DMM easily.

Taking some basic fundamental measurements is the best way to check out a scope less having some complex and expensive test equipment. Congrats on the new tool and great addition to your tools.

Ron

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#### DustinB

##### New Member
Well I got the scope a couple days ago and everything appears to be ok except for a possible problem with the triggering. It took me a little while to get some traces displayed but I've got it figured out mostly. The problem is with using trigger in normal mode. Auto will usually trigger just fine if I have the other settings right. When in normal mode no trace is displayed no matter what I do with the level setting. If I turn it clockwise all the way, as I go back counter-clockwise I can see the trace flash for less than a second, but no matter how slow I go the trace won't stay.

Any ideas what might be the problem or what to try? This is measuring a 12VDC power pack I made(standard ac transformer/FW Rect/Filter Caps/7812). I've read it may be a dirty or failing pot, but I'm hoping it's just my inexperience.

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##### Well-Known Member
If possible measure the AC output from your transformer before the bridge rectifier. Set the scope for Normal triggering after viewing the waveform on Auto triggering. Lets see if that gets you something to look at. Remember the mains frequency for you is 60 Hz. so select a sweep time accordingly. I believe you will see a nice waveform in Normal mode. Note what happens as you rotate the level pot too. Note the slope settings.

Ron

#### crutschow

##### Well-Known Member
Your observation is normal for the Normal Mode, which requires an AC signal to trigger. It's typically used with slow rep rate or single-shot signals where the Auto Mode won't properly sync the signal.

You said you were measuring a 12VDC power pack, so that's why the Normal Mode didn't work -- nothing to trigger on.

Edit: The Auto Mode works by automatically injecting a low frequency sync signal into the trigger circuit to provide a free-run trace when there is no AC signal. When the input AC signal frequency is higher than the free-run sync signal, then it syncs on the external signal. If the input AC frequency is slower than the free-run sync frequency, then it won't properly sync, so you must go to the sync Normal Mode.

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#### DustinB

##### New Member
Thanks for the info. So basically anything I'll be doing with atmega chips and standard circuits will only need auto trigger?

Also BTW, I was able to find the AC signal in the DC. I had to zoom WAY in and turn the brightness all the way up, it was still fairly faint.

#### crutschow

##### Well-Known Member
Thanks for the info. So basically anything I'll be doing with atmega chips and standard circuits will only need auto trigger?

Also BTW, I was able to find the AC signal in the DC. I had to zoom WAY in and turn the brightness all the way up, it was still fairly faint.
Auto Trigger should work for most, if not all, of your typical observations.

Did you have the input on AC coupling when you observed the AC riding on the DC?

What do you mean "zoom WAY in"?

#### DustinB

##### New Member
Yes, I had it switched to AC coupling. By "zoom" I meant the volts/div was at the lowest setting. 2mV/div I believe.

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