Buying a scope and Making sure if it's worth it. - Page 1
Forum section: electronics / beginners

author: laserpon3
author_rank: Contributor
timestamp: June 05, 2013, 08:08:19 pm
content: I've been scope hunting recently as I have a fair "but not high" budget of about 200$ to get a scope. I heard many people saying to get an analog scope (including dave on youtube which also said to stay away from cheapie digital scopes and USB scopes and go for an analog scope).Found myself a Tektronix 2236 on ebay for much less then 200$ sold by a surplus..Scope screen looks ok from pictures, no bumps or crack, nothing blurry or burnt in.Asked the person to run a test on it (which he did according to the manual he had) and this were his results with no signal applied to the scope.Tests > Mem > Rom 0 - PASSEDTests > Mem > Rom 1 - PASSEDTests > Mem > NV Rom - Not ImplementedTests > System > FP A/D - PASSEDTests > System > Comm RB - rb(1)= 0 & rb(0)= 0Tests > System > Comm LB - CAN'T TEST RS232Tests > Acq > Acq IC - ACQ IC TEST PASSED, TRIGGER TEST FAILED, CLOCK INTERPOLATOR TEST PASSED, ACQUISITION RAM TEST PASSEDIs this unit in working operation? I'm not so sure about the trigger test and NV Rom test.Are there ways to have a seller test an unit so I know what I'm buying is in an usable state for tinkering?Thanks in advance for the help.

author: Paul Price
author_rank: Super Contributor
timestamp: June 05, 2013, 09:29:41 pm
content: There is a way, hold a gun to the seller's head.Stuff ends up cheap on Ebay because a piece of equipment has issues and many sellers hope you don't look too carefully and buy.The scope says it has a trigger problem. A scope without a trigger is like the Lone Ranger without a horse.It would probably be difficult to fix for a beginner, and expensive to find someone else with the will and the time to fix it. Find another scope that works.Here's one attached!

author: AlphZeta
author_rank: Regular Contributor
timestamp: June 05, 2013, 10:02:05 pm
content: If it is your first scope, you might want to pass this one. You have a lot of choices for under 200.

author: Anks
author_rank: Frequent Contributor
timestamp: June 05, 2013, 10:07:36 pm
content: the trigger issue is worrying and there is many more out there. If it was me id probably have a look at fixing it but this scope comes from the era that tek started using alot of customs.

author: laserpon3
author_rank: Contributor
timestamp: June 05, 2013, 10:11:08 pm
content: Thanks man! Really apreciate this.Found the ebay offer after some searching.The seller sadly doesn't ship to the Netherlands and with the shipping included it would have costed more then the 200$ I currently have doing freelance work.I Might need to save up longer.I wanted to do some tests with some DAC's I have here to practice programming with vectors and just tinker in general.Anks It was either this one :http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=151057469025&ssPageName=ADME:X:RTQ:US:1123or this one:http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=151055044515&ssPageName=ADME:X:RTQ:US:1123That had the trigger issue (it's the same seller but I think he mixed the 2 up while answering to my reply)

author: Paul Price
author_rank: Super Contributor
timestamp: June 06, 2013, 12:26:10 am
content: http://www.dba.dk/soeg/?soeg=oscilloskopThis a Danmark site that has two 20MHz models this day One for 300DK, one for 250 DK, ($1 US = 5.5DK) <=50 US+Shipping. Nice scopes that are working well for the price. Our Deutchland brothers on EBay.de also has some fine instruments very cheap. Take a little trip to Copenhagen and have a nice vacation or come see the Fatherland.http://www.ebay.de/sch/i.html?_trksid=p5197.m570.l1313.TR9.TRC1&_nkw=Oscilloscopes&_sacat=0&_from=R40Oszilloskop anyone???

author: laserpon3
author_rank: Contributor
timestamp: June 06, 2013, 08:21:05 am
content: That's really tempting!Having an issue deciding between that or a scope I found close to the area I live (That I can pick up).Someone is offering a scope (Tektronix 453) for 100 euro's (however no probes).The frequency is 50mhz and as far as I'm aware it's dual trace, but I think it's lacking a signal generator which I think is a problem to tune the thing to the new probes.Not sure what to go for.

author: Paul Price
author_rank: Super Contributor
timestamp: June 06, 2013, 10:29:39 am
content: All scopes have a calibration square wave output somewhere on the front or side panel for the probes. Only a few companies, like Agilent have had the fanciful idea of including some form of signal generator inside their scopes.

author: EEVblog
author_rank: Unknown
timestamp: June 06, 2013, 10:37:23 am
content: Quote from: laserpon3 on June 05, 2013, 08:08:19 pmNo, I did not say that. That is a very common mis-quote!I said that an analog scope is a lot better than those crappy toy handheld scopes like the DSO nano or a cheapie USB scope.They are also a good learning tool and starter scope for a beginner.But I have never said that an old analog scope is better than a modern cheap bench scope. In fact have said the opposite time and time again.Any modern digital bench scope beats the shit out of any old analog scope.

author: Paul Price
author_rank: Super Contributor
timestamp: June 06, 2013, 11:01:43 am
content: Here's what Davy Jones has to say about it.He highly recommends an analog scope for beginners.EEVblog #86 - Buy a real Analog Oscilloscope PLEASE!EEVblog EEVblog·531 videos-----------------------------------------------------------------This is my rant:Everyone has their own opinion, but an analog scope can't be beat for showing clearly how basic waveforms really look.Digital scopes can easily distort waveforms if their amplitude exceeds the graticule display area.There are major advantages of having a digital scope if you need to capture and see complex digital waveforms clearly. Digital scopes also allow you to see slow moving analog events clearly that the persistence of an analog scope is limited by.But these tasks are not so common nor important to a beginner and complex digital waveforms displayed may not be understood well by a beginner.You need to observe circuit operation to learn about electronics and know that a scope makes this possibleBut be aware of this, even the best digital scopes only approximate the fidelity of view and ease of operation that an analog scope delivers, especially to those just starting to learn beginning electronics.They are also so very easy to use. On an analog scope, all you need to do is twirl the vertical, timebase time/div and trig and you will see the trace you are looking for. while digital scopes can try to do this automatically at a touch of a button, but it often chooses to display the wave form at an inappropriate time/div setting or resets the baseline and the trigger position on the display so that multiple traces are displayed but overlap.Most analog scopes, have such good vertical amp. calibration and easy setup that I often use them to measure DC voltages as good as my eye and just about as good as the DVM next to me can see. I simply place the trace at the bottom graticule and I can then just use the graticule to read out DC voltages with quite good precision and accuracy. Digital scopes give you quite a lot of trouble positioning the baseline easily or even seeing a baseline, are always trying to center the trace vertically with automatic controls, so it is not easy to get a free-running trace at the bottom graticule line quickly for quick DC measurements all around your circuit.Most digital scopes are very careful to always try to automatically position the triggered trace near the center and have to be tediously adj'd with several settings to get the baseline at the bottom of the screen and then to get the trigger point and horiz. reference point set at the beginning of the left side of the graticule.Any digital scope is only trying to emulate what an analog scope can do.Especially when clearly displaying two traces, analog scopes can very much quickly set up correctly to do thisMost low-end digital scope will only trigger on one channel, while an analog scope will often allow you to trigger on two channels when viewing two signals. My 3000 dollar digital scope will allow me to trigger off the AC mains, will not allow me to adj. the trigger level.Digital scopes obey the strange custom of always displaying forever the last triggered pulse, so you could easily be deceived into believing a signal is there when it no longer isn't There is no way to turn this "feature" off.Digital scopes often distort signals because of their very limited horizontal and vertical digitization limitations...and if you've never seen a sinewave in all its pure beautiful curves on an analog scope, you will grow up to believe a sinewave signal has those small horizontal artifact step functions that so clearly betray the limitations of all but the most expensive of digital scopes to display a any waveform with fidelity.In addition, an analog scope is more rugged, it is a lot harder to destroy that old scope with one slip of the beginner's probe onto a high-voltage pulse that would turn your several hundred dollar digital approximation of an oscilloscope into a worthless high techno decoration that no longer functions.There is no argument in my opinion, that analog scopes are cheaper to buy yet offer high performance, and that alone is a great advantage to a beginner.Another handy feature of my analog scope is that its cabinet width exactly matches the feet spacing of my digital scope that sits upon it at a convenient eye level, so I have digital above and analog right below and the digital scope rides the analog like on a saddle on a horse.An analog scope should always be part of an electronics workbench.

author: laserpon3
author_rank: Contributor
timestamp: June 06, 2013, 01:29:05 pm
content: First of all, thanks for clearing that up dave also big fan of your video'sI kinda expected the thing about the digital scopes. I think the rule for digital scopes mostly go's for the low end priced digital scopes.I think an analog scope is best for me, seeing its more durable and cost efficient.Glad to hear every analog scope has a signal generator.I will get the analog scope and get my probes here:http://dx.com/p/100mhz-oscilloscope-probe-32422(It seems to have good reviews).Thanks so much for the help, I really apreciate it and will most certainly share any findings on the forum incase I have some that are of interest.Can't choose between the Voltcraft 630-2 or tektronic 453.Which would you guys say I should get?