Need help choosing to buy an oscilloscope - Page 1
Forum section: electronics / beginners

author: Roka
author_rank: Newbie
timestamp: April 08, 2018, 10:19:54 pm
content: Hi!This is my very first post I don't really know this forum but I am going to give it a shotSo basically I need to get an oscilloscope to finish my school project ( I might post it later) and Ive managed to find a company who sells used ones for dirt cheap.However I cant really make a decision on which one to buy, and I am looking to crowd source some infoHere is the list:Oscilloscope, Iso tech ISR 622 - 20 MHz £30Oscilloscope, Iso tech ISR 650 - 50 MHz £30Oscilloscope, TekTronix 2201 20MHz not calibrated or partly faulty £10Oscilloscope, Hitachi V-423 40 MHz £30Oscilloscope, TekTronix, 2215/A 60 MHz £30Oscilloscope, Iso Tech, ISR 622 - 20 MHz £30At the moment I would pick the Iso tech ISR 650 because its measuring up to 50Mhz and its newer than the others. However I think it is not as well known brand as the others. However the tektronix 2201 would be a storage scope if I could fix it.Any suggestion will be appreciated.Thanks

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2018, 03:18:05 am
content: I'm not familiar with Iso Tech scopes but from that list I think I'd go with the Tek 2215 assuming it's in decent shape. I also don't know what you're doing with the scope but I'm assuming all of those instruments are analog?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: April 09, 2018, 04:28:01 am
content: Tek 2215a or the Hitachi

author: daybyter
author_rank: Frequent Contributor
timestamp: April 09, 2018, 04:33:30 am
content: You did not mention, what kind of signals you want to measure?You often need a scope to repair a scope?If you need a scope for your school work, the school should give you access to one? Or maybe the closest university? A hackerspace near you?Or maybe a USB scope works for you? See the hantek 6022be thread as an example.

author: ebastler
author_rank: Super Contributor
timestamp: April 09, 2018, 04:38:01 am
content: Assuming that all scopes are in comparable shape, the Tek 2215 seems like the best deal. It comes from a major brand and is well-documented. (Service manuals/schematic are available, and you are more likely to find someone in internet forums etc. who can help with questions or troubleshooting.) It also happens to have the highest bandwidth of the scopes you are considering.Worth checking: Do those used scopes come with probes? New Chinese probes on ebay are not that expensive, if you have to buy them extra, but their cost is not negligible vs. the scope itself.

author: Electro Detective
author_rank: Super Contributor
timestamp: April 09, 2018, 04:41:59 am
content: Hey mate, welcome to the forum and I reckon any one of those models abovethat works perfectlyis the winnerotherwise the one you like the most may be the most troublesome =The one that works perfectly can be used to fix a second oscilloscope if you decide that two is better than one...I'm guessing there's no shortage of members here that sort of think that way

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2018, 04:42:52 am
content: Another issue with the Chinese probes is that most don't support the probe coding that Tek uses, I don't know if any of those other scopes have means to detect 1x/10x probes.

author: lem_ix
author_rank: Regular Contributor
timestamp: April 09, 2018, 09:29:10 am
content: Those Iso tech scopes are GW Instek scopes. Not bad at all. Can even find schematics for some.

author: Roka
author_rank: Newbie
timestamp: April 09, 2018, 09:45:39 am
content: Thanks for the replies.Yes in the meantime I had a look at the Tektronix myself as well, because i totally missed the 60Mhz one,I had a look online and even managed to find a full manual for it in no time, however I found nothing for the Iso tech.Well I always wanted to buy an oscilloscope but I couldnt really afford it, until now as they getting cheaper and cheaper.The task I want to use it for at the moment is to measure the current demand, and the effect on the voltage of the power supply for a stepper motor as it constantly work in a start-stop mode.Thank you very much for the help, I was considering to do a calibration on the scope as I have found a great video from Alan, the manual for the scope, however I am not really sure the cost of the higher precision signal generator, multimeter I would need for the task. Has anyone done something like that here before?https://www.youtube.com/watch?v=SsoAe0kMYfc&feature=youtu.beCheers

author: vk6zgo
author_rank: Super Contributor
timestamp: April 09, 2018, 10:26:06 am
content: Quote from: ebastler on April 09, 2018, 04:38:01 amI would go with the Tek 2215 because it has a delayed time base.You may think you would never need that facility, but once you learn how to use it, you will wonder how you got on without it.The other 'scopes all seem like quite good units, & as I have said on other occasions, you can do good work with quite basic Oscilloscopes, but the better instrument you can get for your budget, the more useful it will be.

author: james_s
author_rank: Super Contributor
timestamp: April 09, 2018, 05:46:41 pm
content: Don't mess with the calibration unless you are positive it is out of spec and are sure the scope itself is not malfunctioning. My nearly 40 year old Tek 465B has not been calibrated since sometime in the early 90s and it's still plenty accurate. An oscilloscope is not a precision measurement device in the first place, you can check it against some basic signals of known voltage and frequency and if it's pretty close it will be good enough. Calibration is needed when you're taking measurements that have to be certified against some known standard, which as a hobbyist I doubt you'll be doing.

author: Old Printer
author_rank: Frequent Contributor
timestamp: April 10, 2018, 07:41:40 pm
content: I also wouldn't worry about the "TEK" compatible probe thing too much. When the proper scope is matched with the proper probe the scope will automatically adjust the trace to compensate for the 1x - 10x vertical change. If you had to buy a new TEK probe to accomplish that it might cost more than the scopes you are looking at. If you use a generic probe you will just have to be aware that the vertical (amplitude) setting will need to be matched to the setting on the probe. This is an excellent video by Alan Wolke on the subject.

author: Roka
author_rank: Newbie
timestamp: April 10, 2018, 07:50:54 pm
content: Yeah I had to buy probes for it aswell.Ive got these ones, they have the 1-10 thing aswell which i need to calibrate. apparently they are for tektronix.When i said calibrate i meant to adjust the scope internally, but since i dont have proper signal generator or expensive multimeter i wont do it for now.https://www.amazon.co.uk/gp/product/B073GRYRCD/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

author: Old Printer
author_rank: Frequent Contributor
timestamp: April 11, 2018, 12:52:36 am
content: Those are generic Chinese probes. They will work with the 2215 and most any other scope as well. They do not have the built in sense ring and third wire to activate the Tek auto 1x - 10x compensation feature. You will likely need a Tek brand probe to do that. I don't know which Tek probes will enable that feature, but others here might. It is a convenient feature, but hardly necessary as long as you are aware to make the compensation manually. My Tek 475 has that feature, but my 2225 does not. Good luck with your new scope!

author: james_s
author_rank: Super Contributor
timestamp: April 11, 2018, 12:59:51 am
content: You can get Chinese probes that support the probe coding but they are harder to find and more expensive. You can also add it yourself, it's just a resistor, and some mechanical bits, perhaps a pogo pin would do the job?You should not need to calibrate the scope unless it has been messed with. Certainly not to use different probes, perhaps you're confusing calibration with compensating the probes?

author: Roka
author_rank: Newbie
timestamp: April 11, 2018, 07:19:29 pm
content: Well I was really happy when i got it but it turned out that it has an intermittent fault on the screen where it doesnt use up the whole width of the crt, plus really loud coil noise from the high voltage part. oh yeah and wobbly and loose potmeter for the trigger and the timed delay stuff. So i will try to get them to exchange for me for a different one. i probably end up choosing the tektronix 2201 even tho its lower in bandwidth as its only 20MHz but it has storage facility. Altough Im not sure just yet, I might up getting the Hitachi or the Iso-tech after all.Thoughts?

author: james_s
author_rank: Super Contributor
timestamp: April 11, 2018, 07:57:17 pm
content: That looks like what happens when one of the wires falls off the deflection connection on the CRT. If it were me I'd open the thing up and try to fix it, any cheap used instrument is likely to have *something* wrong and overall this looks pretty good. It's worth at least checking the deflection connections, the whine is likely due to the power supply needing some new capacitors, this is also fairly common.

author: Mr. Scram
author_rank: Super Contributor
timestamp: April 11, 2018, 08:06:57 pm
content: Quote from: james_s on April 11, 2018, 07:57:17 pmI was thinking the same. If the screen works, but has a problem displaying one area there's a good chance it's one or more of the coils. Just make sure not to poke around while it's powered, unless you are very sure what you're doing.

author: Distelzombie
author_rank: Frequent Contributor
timestamp: April 11, 2018, 08:07:31 pm
content: How much are you paying for them? I was observing the used-market for month and Tektronix doesn't seem worth it unless you are a collector. Also, you are paying about 150$ in the end (Calibration, repair, probes...) for hardware that is 20 to 30 years old and is already failing. Double that and you can get a new Siglent with 200MHz that will probably work for your own next 20 years. Buy that Siglent with "installment payment" or whatever it is called where you live, and you don't even need to worry about spending more than 30$ per month.I said I was observing the used market, there's seriously nothing that beat buying new, unless someone gifts you one. It appears the reason yours are dirt cheap is because they don't work. That was a good option 6 or 7 years ago when new scopes cost about 1000$, but now there's just no justification for some non-collector, I think.

author: Roka
author_rank: Newbie
timestamp: April 11, 2018, 08:16:45 pm
content: This was 30 pounds in the uk, however the other tektronix2201 is only 10 pounds because apparently something is wrong with it. I wouldnt mind fixing the thing I am just not quite sure If I can get parts for it, like the pots? or maybe other stuff. I actually open it up and tried to look for the contact fault, however just moving wires around didnt seem to change anything. I didnt have time to look int othe schematics just yet. I also have no chance of getting a high voltage probe to test all parts of the crt. So since I only got the thing today I thought it would be easier to swap it to something that works or have less problems.probes were 10pounds

author: james_s
author_rank: Super Contributor
timestamp: April 11, 2018, 10:05:39 pm
content: 10 pounds seems like a good deal for something that's likely fixable. It can be a bit tricky to find parts like pots, but they can be had from parts scopes, usually those with a bad CRT and usually pots don't need to be replaced. Calibration is not an issue, for a hobbyist you don't need it and it would be silly to pay the money to have it calibrated. As I said earlier, calibration is for when you're doing some sort of testing where everything has to be certified, like an ISO9000 shop.The deflection pins are on the side of the CRT neck, there's an opening in the metal shield around the CRT and they poke through there and slip onto pins protruding from the glass neck. I had one pop off in my Tek 465 once and it did the same thing.

author: Roka
author_rank: Newbie
timestamp: April 11, 2018, 10:18:11 pm
content: Yeah, Well I actually managed to find the fix for that in a video herebut im still concerned that B channel trigger pot needs replacement and about the loud whine coil sound as im surfing the internet for a while now but i couldnt find any parts yet. plus the bad cosmetics like the dials for the voltage knobs are unreadable. So im still wondering if i want to swap it for the 2201 because that has storage feature and might have less problems on it. Or just get that one aswell and keep this one for a later project as 30 pounds is still good for it even if its only bought for parts.

author: Roka
author_rank: Newbie
timestamp: April 11, 2018, 11:44:51 pm
content: A heck it, I will just buy the other one aswell since the 2201 is only a tenner and I will fix them up somehow. My problem solving fixing skill needs some dusting anyway since its been a while I repaired something. I got encoured by all the videos on youtube how other people fixed their Tektronix (especially the EEVblog guy with his incredible knowledge and majestic accent) Thanks guys I might post another post if Im stuck with the repair

author: james_s
author_rank: Super Contributor
timestamp: April 12, 2018, 12:24:23 am
content: There you go, now you'll have a second scope you can use to fix the first scope, pretty soon you'll probably end up with a few more scopes, I think maybe they breed, at least that's what I tell my other half

author: Electro Detective
author_rank: Super Contributor
timestamp: April 15, 2018, 02:10:37 am
content: Quote from: james_s on April 12, 2018, 12:24:23 amYes, they're like cats n kittens,and need a good home in the meantime...

author: Roka
author_rank: Newbie
timestamp: May 10, 2018, 06:45:32 pm
content: Allright guys here is a little updateI have tried to repair the CRT connection on the 2215 by resoldering a hundread connection around on the mainboard but with no luck.Since you need an oscilloscope to fix an oscilloscope Ive bought another oneAND I GOT JACK POTan ex school Tektronix 2430A 150Mhz from ebay with PAT test sticker expirity of 2018 aprilwhich is fully working! I couldnt be any happier. I might try to fix the other one, once I have finished my exams for HND.Cheers