Scope triggering , need help - Page 1
Forum section: electronics / beginners

author: cleanworkbench
author_rank: Regular Contributor
timestamp: November 30, 2017, 02:49:45 pm
content: 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

author: macboy
author_rank: Super Contributor
timestamp: November 30, 2017, 03:03:26 pm
content: 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.

author: fcb
author_rank: Super Contributor
timestamp: November 30, 2017, 03:13:32 pm
content: 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...

author: w2aew
author_rank: Super Contributor
timestamp: November 30, 2017, 03:45:19 pm
content: Quote from: cleanworkbench on November 30, 2017, 02:49:45 pmAs 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:

author: cleanworkbench
author_rank: Regular Contributor
timestamp: November 30, 2017, 04:41:27 pm
content: Thanks for the repliesWell 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.

author: w2aew
author_rank: Super Contributor
timestamp: November 30, 2017, 05:50:57 pm
content: If you could provide a clear picture of the front panel of your scope, we could then advise you how to set it up.

author: danadak
author_rank: Super Contributor
timestamp: December 01, 2017, 12:06:21 pm
content: http://www.radio-electronics.com/info/t_and_m/oscilloscope/oscilloscope-trigger.phpRegards, Dana.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 03, 2017, 01:12:21 pm
content: I will try and get a photo of the scope uploaded .

author: danadak
author_rank: Super Contributor
timestamp: December 03, 2017, 03:37:42 pm
content: The 240 is a 2 channel version of 140 -Regards, Dana.

author: w2aew
author_rank: Super Contributor
timestamp: December 03, 2017, 03:44:58 pm
content: 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.

author: danadak
author_rank: Super Contributor
timestamp: December 03, 2017, 04:01:15 pm
content: In addition set your gain so that you see at least 2 major divisions ofwaveform pk-pk.Regards, Dana.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 03, 2017, 07:16:03 pm
content: yep, that,s the scope ive got just its a single channel job. Will try your suggestions for triggering .Many thanks for replies.

author: StillTrying
author_rank: Super Contributor
timestamp: December 03, 2017, 09:34:49 pm
content: I've often seen that type of slide switches become intermittent with age, or even fall to bits.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 04, 2017, 08:20:14 am
content: 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.

author: tautech
author_rank: Super Contributor
timestamp: December 04, 2017, 08:28:06 am
content: Quote from: cleanworkbench on December 04, 2017, 08:20:14 amInternal triggering is indeed requiredandthe level set within the amplitude of the waveform.Enjoy your visions into a new world.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 04, 2017, 09:14:49 am
content: Yeah thanks mate its a new door opening for me .

author: mikerj
author_rank: Super Contributor
timestamp: December 04, 2017, 09:54:17 am
content: Quote from: cleanworkbench on December 04, 2017, 08:20:14 amIt will almost certainly be in the range 10MHz-20MHz.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 04, 2017, 10:45:59 am
content: Ok, not fantastic by today's standards but still very useful. Thanks for the info.

author: danadak
author_rank: Super Contributor
timestamp: December 04, 2017, 12:20:18 pm
content: Internet hit shows 10 KMhz. If its a tube scope consider testing tubesin 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_capacitorsRegards, Dana.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 04, 2017, 04:26:02 pm
content: Hmmm , thanks, i will have the case off and inspect.

author: danadak
author_rank: Super Contributor
timestamp: December 04, 2017, 05:28:58 pm
content: Here is a scope and sig gen and spectrum analyzer (free) that uses sound card in your PC -https://www.zeitnitz.eu/scope_enProtect your sound card inputs against damage -http://www.pmillett.com/ATEST.htmhttp://www.daqarta.com/dw_0all.htmhttp://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.htmRegards, Dana.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 05, 2017, 09:35:00 am
content: Thanks for the links , i will give em a look. Looks very interesting .

author: james_s
author_rank: Super Contributor
timestamp: December 05, 2017, 09:03:35 pm
content: 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.

author: danadak
author_rank: Super Contributor
timestamp: December 05, 2017, 11:24:07 pm
content: Tek 70 catalog still dominated by tube scopes. At NSC late into 70s still545 main scope in factory.Tube scopes still great, especially plugin series where they addressed specializedneeds. And a tube scope is, unlike solid state/integrated circuit, tough to kill.Lastly great as a heater....Regards, Dana.

author: james_s
author_rank: Super Contributor
timestamp: December 06, 2017, 12:54:29 am
content: 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.

author: danadak
author_rank: Super Contributor
timestamp: December 06, 2017, 12:07:56 pm
content: Actually most of those offerings are general purpose. Its the plugin variabilitythat allows one to deviate mainframe from a generic scope and solve a particularmeasurement problem.Take a look at catalogs -http://w140.com/tekwiki/wiki/Tektronix_CatalogsThe 545 in particular was mainstream scope in many companies. It would be interestingto know how many total were sold. I am guessing jillions.The best of both worlds.There are specialized, at the time 519 would be considered that, or dual beam, but they werenot its core business. My observations based on activity as an FAE calling on many companiesin Northeast.But en total they were in the mainstream scope business. Lab grade. Not in competition withEico or Heathkit or Knightkit.Regards, Dana.

author: cleanworkbench
author_rank: Regular Contributor
timestamp: December 08, 2017, 10:47:46 am
content: Had the base cover and it is 100% solid state , except for the tube of course. And the best thing is it has an ident tag and on that it reads " MADE IN ENGLAND " !!!!! nuff said Hurrah. Its a keeper.