#1
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Tektronix 2205 Oscilloscope with flashing trace..
I bought this Tektronix 20Mhz scope to increase my knowledge and capabilities in radio and TV troubleshooting. All of the functions seem to work, but the trace constantly flashes. I have seen videos on YouTube of other scopes and some do the same thing and others have a nice, non strobing waveform.
I'm just wondering if anyone knows about this. Is it normal for some models or is it a defect. It's not actually strobing, but more of a rather large variation in intensity on a steady and constant frequency. It is less disturbing of course if I turn the intensity down low. I am thinking that when there is no signal applied that the flat line is steady. Any advice here would be greatly appreciated
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#2
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Make sure the sweep mode isn't in chop or alternate - both will give a strobed effect to the sweep. At slower sweep speeds, this effect is quite noticeable.
I generally use auto sweep, one channel, and trigger on that channel. I rarely use more than one channel when using my scope (with 5 channels!). Hope this helps,
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Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#3
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OK Brian, I will check my settings. Also, I need to find two cables for my scope. One would be BNC to BNC to run from my function generator to the scope. Another would be a BNC with alligator clip ends to apply signals from the generator to a circuit. Not that my lack of having these is the problem.
Just figured I would mention it because I was using an O scope probe to apply and/or measure signals from the generator until I found out that evidentally all scope probes are made with resistance wire. Someone on another page mentioned a need for the same thing as I and they thought that they could just cut the probe off and add some clips. Not quite that simple.....
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#4
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If you have the trigger level set near zero, random noise will trigger the sweep intermittently. If you turn the trigger level up or down, two things can happen:
1) sweep stops completely (trigger not on auto) 2) sweep becomes steady (trigger on auto) |
#5
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Quote:
I tried everything mentioned thus far and every other combination of the many (too many) settings and nothing will give me that rock steady trace that I would like to have and have seen on even the oldest of units. Again though I have seen others that do the same thing in YouTube vids, but the videos I have seen it in are not about this particular issue. All in all I like this scope. Once the college loaned me one of their digital pieces of junk in my opinion and I quickly realized why my professor had the labs set up with analog scopes. Admittedly, I know that digital units have come a long way and I would hope so as much money as can be spent on one. I guess there is at least one good reason why I am not an engineer which would be about the only reason I think that you would need the numbers and capabilites of the new generation of scopes. They say there are a few odd ball guys in the upper echelons of electronics that still use older analog equipment, but supposedly they get a lot of ribbing from their peers. Sort of like me taking my Simpson 260 to work and getting 'the look', even from my boss who I went to school with. Funniest thing is one day we had a piece of equipment with a bad potentiometer. The house Fluke 5 had some issue besides the mind boggling array of way too fast moving numbers. So it was Simpson to the rescue. Of course I was the only tech there who could operate it. My boss tried to brush off the embarrassment of not being the superior being my telling me that it was too old and could only measure 10Kohms (the highest selection) and we had a larger pot. I tried to explain multipliers, but time has moved forward too far I guess. People now just want everything simple, easy and basically done for them without thought. I did at least get to prove the undeniable tool that the analog meter is in this particular instance by showing them the sweep of the dial indicator up to the problem point within the potentiometer. I better stop before I go on another rant about the dumbing down of electronics. In a sentence at least, you simply don't need to know what you used to.....
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#6
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Working, left to right, choose channel 1, norm, alt, mid-to-fast sweep speed (1msec/div or faster), trigger centered (slope switch to either setting for now), sweep mode to PP-Auto, source to channel 1 or vert mode. Quote:
Cheers,
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#7
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OK Brian, thanks again. I am not home with the scope at the moment, but will try what you mentioned as soon as possible. That story about Jim Williams is quite refreshing. Sometimes I feel as if my 'analog' ways will leave me behind in the electronics world, or more specifically; on the job.
I guess it's really a matter of what facet of electronics you are involved with and/or interested in. I find low voltage semiconductor, microchip stuff to be a bore personally, but I must accept and understand it to a certain degree to be any kind of a tech these days. I really wish that I lived near one of the music amplifier companies that still produce vacuum tube equipment, or even some service center for that matter. It just doesn't exist anywhere near my home here in VA. It would be great though even to be involved in the production of that equipment. There should still be some home audio companies producing tube amplifiers. I know that big component stereo equipment like so many things is suffering a decline in interest due I guess to the Ipods and smart?phones.
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"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
#8
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Quote:
Quote:
Cheers,
__________________
Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#9
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matching item on it, and includes a trim cap that you make sure the little test wave looks square when tested. It's on the front of that scope, 1khz test I think it says... 1khz at something like .5v... if the probe has also a 10X divider built in, you will have a switch that will divide your signal source by 10. 100v signal will max at 10v. I use to use home made probes with rg6 and connectors from RS, just be careful where you stick it, you don't wanna overload the vertical amplifiers in the scope. AND most important, check to be sure your potential between ground for the scope, and ground on yer test item is 0V. Be aware Hot chassis sets can make cool sparks shows if you ground a ground to a not so ground ground. Also check the sensitivity of the brightness control, it may be noisy and flash the screen. But mostly as mentioned, the sync will flash the screen if it's not running freely enough. If you hook up your ch1 to the test point, and sync off ch1 as well, you should see a stable square wave, and the sync should lock, and you should be able to get a stable screen... turn the variable sync threshold you should see it lock at one end, and maybe even stop scanning, and lose sync at the other extreme... .
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Yes you can call me "Squirrel boy" Last edited by Username1; 10-12-2014 at 03:44 PM. |
#10
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I copied this from the other thread that I made that can be found in Vintage Test Equipment. I think I titled it WTB Two Sets of Leads. At any rate a good fellow who calls himself NoPegs posted this and the link to a YouTube video that explains what I was trying to say. And yeah, I'll watch out for a ground loop. Your mention of transformerless "hot" chassis leads me to something that I have wondered for a while, but never posted anything about. What is the approach to using a scope or even other test equipment with a "hot" chassis? I'm sure it's simple and I will fell dumb when I hear the answer. Would an isolation transformer be the right way to go?
So anyway, here goes with what NoPegs said and that link: "The old scope probe is a no-go my friend. In short, they're not built with normal coax. For more detail you can watch https://www.youtube.com/watch?v=OiAmER1OJh4"
__________________
"Face piles of trials with smiles, for it riles them to believe that you perceive the web they weave, and keep on thinking free" |
Audiokarma |
#11
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The scope will have a three prong grounded plug. Use it with a correctly wired three prong grounded electrical outlet and do not try to defeat it in any way. If you trip a breaker or GFI socket, it is evidence that something is dangerously wrong with your setup. |
#12
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Of course it depends on the application. The measurements made with an oscilloscope are only as good as the oscilloscope and the probes that are used. I am posting a clickable link to Tubejunke's information just to make it easy because it is some great information for those that are interested. |
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