Author Topic: Scope triggering , need help  (Read 1037 times)

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Offline cleanworkbench

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Scope triggering , need help
« on: December 01, 2017, 01:49:45 AM »
Hello everyone , i,m a newbie here.
Getting back into electronics after many years away from it .
I have just built a single transistor sine wave phase shift oscillator and have the trace on the scope . The scope is a cheap single channel job from the UK circa 1970s a Gould OS 140.
On the front panel there are two 4mm sockets marked Gnd and the other Ext trig / X, next to that is a small insulated pin marked Gate o/p I have no manual on the instrument . However i want to stabilize the sine trace so i need to trigger it with a square wave , right ?.
I,m not sure how to, do i plug the gate o/p into the trig socket or make up a 555 square wave generator say 1khz and put that into the ext/ trig socket , i,m a bit lost here . Can someone clarify please.

Thanks
 

Offline macboy

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Re: Scope triggering , need help
« Reply #1 on: December 01, 2017, 02:03:26 AM »
Most of the time, the trigger is set to the signal itself. You absolutely can trigger from a sine wave.
If your oscillator is producing a stable signal, and the oscilloscope is not faulty, then you should be able to obtain a nice stable display.

You will not get a stable display by triggering from a completely unrelated (uncorrelated) signal, such as a separate 555 timer. Since the trigger is unrelated to the signal, the scope will start to display the waveform at an essentially random point each time it redraws the screen. At best, the signal will wander or drift left or right, at worst you will just see a garbled mess.

It might help if you can take a clear photo of the front panel of your oscilloscope, set up the way you are trying to view your oscillator signal. People here may be able to find errors in the settings you are using and give you more specific advice.
 

Offline fcb

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Re: Scope triggering , need help
« Reply #2 on: December 01, 2017, 02:13:32 AM »
Is there a selector on the scope to choose the trigger source, probably with two to four options Free, A, EXT or Line?

If you can't trigger off your input by selecting it on the trigger module, then try daisychaining your signal into the external trig.  This assumes that this section is working...
 

Offline w2aew

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Re: Scope triggering , need help
« Reply #3 on: December 01, 2017, 02:45:19 AM »
Hello everyone , i,m a newbie here.
Getting back into electronics after many years away from it .
I have just built a single transistor sine wave phase shift oscillator and have the trace on the scope . The scope is a cheap single channel job from the UK circa 1970s a Gould OS 140.
On the front panel there are two 4mm sockets marked Gnd and the other Ext trig / X, next to that is a small insulated pin marked Gate o/p I have no manual on the instrument . However i want to stabilize the sine trace so i need to trigger it with a square wave , right ?.
I,m not sure how to, do i plug the gate o/p into the trig socket or make up a 555 square wave generator say 1khz and put that into the ext/ trig socket , i,m a bit lost here . Can someone clarify please.

Thanks

As others have stated, you likely want to set the Trigger Mode to "Internal" to trigger the sweep to the signal itself.
This old video of mine might help, even though the scope is different than what you have, the controls will likely be somewhat similar:

======================================
YouTube channel: http://www.youtube.com/w2aew
FAE for Tektronix
 

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #4 on: December 01, 2017, 03:41:27 AM »
Thanks for the replies
Well its back to basics here on a budget !!!.

Yes i thought it would have to be triggered by the sine wave and not an independent circuit , so what your saying is possibly a  555 sine to square wave converter tapped onto the phase shift sine wave output and then fed into the external trig socket and the scope lead also onto the phase shift sine wave o/p .
I,ve tried switching to internal but the trace still moves slightly, to control the position of the trace i have to adjust the " variable cal in the the time / div sector , or am i totally confused here .
I will look at the you tube vid.
 

Offline w2aew

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Re: Scope triggering , need help
« Reply #5 on: December 01, 2017, 04:50:57 AM »
If you could provide a clear picture of the front panel of your scope, we could then advise you how to set it up.
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Offline danadak

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Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #7 on: December 04, 2017, 12:12:21 AM »
I will try and get a photo of the scope uploaded .
 

Offline danadak

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Re: Scope triggering , need help
« Reply #8 on: December 04, 2017, 02:37:42 AM »
The 240 is a 2 channel version of 140 -




Regards, Dana.
 

Offline w2aew

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Re: Scope triggering , need help
« Reply #9 on: December 04, 2017, 02:44:58 AM »
Try setting the trigger slope to +, the Function to AC, the Trig Sel to Y1 and adjust the Level up and down until you have a steady display of your waveform.
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Offline danadak

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Re: Scope triggering , need help
« Reply #10 on: December 04, 2017, 03:01:15 AM »
In addition set your gain so that you see at least 2 major divisions of
waveform pk-pk.


Regards, Dana.
 

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #11 on: December 04, 2017, 06:16:03 AM »
yep, that,s the scope ive got just its a single channel job. Will try your suggestions for triggering .
Many thanks for replies.
 

Offline StillTrying

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Re: Scope triggering , need help
« Reply #12 on: December 04, 2017, 08:34:49 AM »
I've often seen that type of slide switches become intermittent with age, or even fall to bits.

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #13 on: December 04, 2017, 07:20:14 PM »
Yes the switches are a bit dodgy but its all ive got  !!!. It needs a teardown and some tlc, it was a freebe years ago.
Well i have had success with the triggering , i flipped the slider switch to internal and rotated the trigger level pot and hey presto a stable trace dont know why i never went to the level pot before , old age i guess LOL.
So i,m a happy bunny now .
Just curios about the OS140 scope , what bandwidth is it rated at , i have no data sheet or manual on it .
Thanks to you all for the input.
 

Online tautech

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Re: Scope triggering , need help
« Reply #14 on: December 04, 2017, 07:28:06 PM »
Yes the switches are a bit dodgy but its all ive got  !!!. It needs a teardown and some tlc, it was a freebe years ago.
Well i have had success with the triggering , i flipped the slider switch to internal and rotated the trigger level pot and hey presto a stable trace dont know why i never went to the level pot before , old age i guess LOL.
So i,m a happy bunny now .
Just curios about the OS140 scope , what bandwidth is it rated at , i have no data sheet or manual on it .
Thanks to you all for the input.
Internal triggering is indeed required and the level set within the amplitude of the waveform.

Enjoy your visions into a new world.  :)
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Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #15 on: December 04, 2017, 08:14:49 PM »
Yeah thanks mate its a new door opening for me .
 

Offline mikerj

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Re: Scope triggering , need help
« Reply #16 on: December 04, 2017, 08:54:17 PM »
Just curios about the OS140 scope , what bandwidth is it rated at , i have no data sheet or manual on it .

It will almost certainly be in the range 10MHz-20MHz.
 

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #17 on: December 04, 2017, 09:45:59 PM »
Ok, not fantastic by today's standards but still very useful. Thanks for the info.
 

Offline danadak

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Re: Scope triggering , need help
« Reply #18 on: December 04, 2017, 11:20:18 PM »
Internet hit shows 10 KMhz. If its a tube scope consider testing tubes
in it, ones in trigger path that grow weak will affect triggering capability.
Also if black beauty caps in scope replace them all -

http://w140.com/tekwiki/wiki/Bumble_Bee_capacitors


Regards, Dana.
 

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #19 on: December 05, 2017, 03:26:02 AM »
Hmmm , thanks, i will have the case off and inspect.
 

Offline danadak

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Re: Scope triggering , need help
« Reply #20 on: December 05, 2017, 04:28:58 AM »
Here is a scope and sig gen and spectrum analyzer (free) that uses sound card in your PC -


https://www.zeitnitz.eu/scope_en


Protect your sound card inputs against damage -


http://www.pmillett.com/ATEST.htm


http://www.daqarta.com/dw_0all.htm


http://www.electro-tech-online.com/threads/soundcard-oscilloscope-protection.92122/


And some more sound card instruments (note the RLC meter link) -


http://www.radio.imradioha.org/PC_Based_Test_Gear.htm



Regards, Dana.
 

Offline cleanworkbench

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Re: Scope triggering , need help
« Reply #21 on: December 05, 2017, 08:35:00 PM »
Thanks for the links , i will give em a look. Looks very interesting .
 

Offline james_s

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Re: Scope triggering , need help
« Reply #22 on: December 06, 2017, 08:03:35 AM »
Pretty sure it's solid state, tubes aside from the CRT were pretty much out of scopes by the end of the 60s, aside from a few specialized beasts.
 

Offline danadak

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Re: Scope triggering , need help
« Reply #23 on: December 06, 2017, 10:24:07 AM »
Tek 70 catalog still dominated by tube scopes. At NSC late into 70s still
545 main scope in factory.

Tube scopes still great, especially plugin series where they addressed specialized
needs. And a tube scope is, unlike solid state/integrated circuit, tough to kill.

Lastly great as a heater....



Regards, Dana.
 

Offline james_s

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Re: Scope triggering , need help
« Reply #24 on: December 06, 2017, 11:54:29 AM »
I would classify most of those Tek tube scopes as "specialized beasts". They are works of art too, I had a 531A for many years until I passed it on to someone else.

Every small low-medium bandwidth bench scope I've seen from the 70s-on has been solid state.
 


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