Help choosing a used scope - Page 1
Forum section: electronics / testgear

author: greg_gorrell
author_rank: Newbie
timestamp: March 14, 2017, 02:58:26 pm
content: Hello all,I have been browsing the forums and watching the videos for a year or so now and finally decided to register. Been into electronics for most of my life but now I am getting into the market for a scope. I have the following for sale locally that I can purchase:Tektronix 5110 for $50 - This comes with a differential amp 5a19n and time base 5b10. The only issue I see is that there are no probes and the granicule backlight isn't working which is no big deal. Also, I'm not sure about it only being a 2MHz scope, but I am a beginner and sometime in the future I could upgrade.LG OS-5100 for $135 or best offer - in good working condition, includes a 100 MHz testing lead and that's about all the information I have on it. It's a two hour drive away from me but looks very well taken care of.Elenco MO-1252 for $200 - I'm sure the price is negotiable and this also comes with the probes. This is a 35MHz dual channel model and comes with original manual.I'm guessing the LG is going to be the best value but I don't know and would greatly appreciate any advice from the pros. Thanks in advance everyone.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: March 14, 2017, 03:05:13 pm
content: Stay away from the 5110. Bandwidth is too low to be of any use.LG OS-5100 is the better scope on that list but the price is way too high IMHO. I've had a couple of their older 20MHz units and they are rebrands of Chinese generic ones. usually pretty easy to fix if anything goes bang. Not the best scopes on the market though

author: nctnico
author_rank: Super Contributor
timestamp: March 14, 2017, 03:11:23 pm
content: Location? There are lots of analog GW Instek scopes on Ebay from the US which seem to be in good condition.

author: greg_gorrell
author_rank: Newbie
timestamp: March 14, 2017, 03:48:34 pm
content: Thanks, I'm in North Central Pennsylvania but most of these are by Buffalo or Rochester, NY.I don't want to have to pay for shipping on eBay as most people want like $30 to $50 extra. When I search for that LG, most all of them are some Chinese variety and not nothing t?he LG model, so it does look like they just slapped their name on it. Maybe if I can get them down to $75, would that be worth it?Should I just hold off and see if anything else pops up of the next couple months?

author: gnavigator1007
author_rank: Unknown
timestamp: March 14, 2017, 04:08:40 pm
content: I'd recommend looking at at the GW Instek again. I see a GOS-6112 up for $119.38 with free shipping and another for $95.99 + shipping, but it's located in Pennsylvania. Also, $30-$50 shipping is not necessarily unreasonable especially for older crt scopes

author: james_s
author_rank: Super Contributor
timestamp: March 14, 2017, 06:57:43 pm
content: What do you want to use the scope for? I would also recommend against anything low bandwidth, I'd say 50MHz is about the minimum that is useful for anything more than very basic stuff or learning to use a scope in general. If you can find one, the Tektronix 465B is a wonderful analog scope, top notch in its day it's still a useful instrument. The newer 22xx, 23xx and 24xx series are nice too but you have to be careful as they use a number of custom hybrid chips that are no longer available except from a parts scope. You can easily spend more by trying to save money in the short term. If you buy a scope that turns out to be inadequate, you will just have to buy another scope later. Also don't overlook probes, good probes can cost as much or more than you pay for the scope and cheap probes can lead to all manner of frustration.

author: greg_gorrell
author_rank: Newbie
timestamp: March 14, 2017, 07:12:22 pm
content: Great information guys, thanks. I plan on using it just for hobby type stuff. I do work on car amplifiers occasionally, but I just want one to have when I do need it. Im just getting into Arduino and various microcontrollers so if I don't exactly have a particular use for it just yet.I wouldn't mind even a newer one but I always saw the older CRT scopes basically being given away or thrown out but now that I want one I'm figuring on laying around $100. I will check again on eBay, bit if there are any decent used digital scopes, I'd even be interested in them. I guess I could pay up to $150 but I hate to buy one for $500 and then never have a real need for it.

author: james_s
author_rank: Super Contributor
timestamp: March 14, 2017, 07:50:20 pm
content: I would expect you could find an older Tektronix analog scope within your $100 budget.Just the other day I saw a Tek TDS540A with a few issues go for only $102.50, that's a 4 channel 500MHz DSO, rather high end in its day. People just don't want these bulky CRT based boat anchors but they're lovely instruments. Most of the problems come from leaky SMT electrolytic capacitors and worn attenuator relays. I think for a beginner an analog scope is probably a good place to start, my point is just that even very nice stuff goes for very little sometimes. Everyone wants the little lunchbox DSOs these days.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: March 14, 2017, 08:32:23 pm
content: This. I just paid equiv $60 for a working Tek 475 analogue delivered to my door. 200MHz bandwidth.Old DSOs are trouble as a rule. They fail cal, have NVRAM which is difficult and expensive to replace and are chock full of ASICs that are irreplaceable, most of the parts are unlabelled surface mount and most of them have no service information available other than replace FRUs. I'd only buy an old analogue or a brand new DSO these days myself. And I don't need the latter so I've got old analogue ones.

author: nctnico
author_rank: Super Contributor
timestamp: March 14, 2017, 08:36:11 pm
content: Tektronix TDS500 and TDS700 series are easy to fix as long as there are no more than two errors in the startup screen and there is tons of information (including component level manuals) out there. ASIC failure is extremely uncommon in these scopes and the NVRAM can be fixed or replaced easely.

author: David Hess
author_rank: Super Contributor
timestamp: March 14, 2017, 08:41:48 pm
content: Quote from: greg_gorrell on March 14, 2017, 02:58:26 pmA Tektronix 5110 is both too old and too slow to be a good choice unless you have a specific use for it. For some people it might be acceptable as a second oscilloscope with its 5A19N vertical amplifier which has some unique capabilities. Mainframe type oscilloscopes are more suitable for people who are going to make a continuing investment in plug-ins.20 MHz is the absolute slowest I would recommend for a general purpose oscilloscope.Quote from: greg_gorrell on March 14, 2017, 03:48:34 pmShipping on Ebay is a definite cost and risk although sometimes you can find sellers in your local area who will allow you to pick it up yourself.Since you are in an area where a lot of used test equipment is available in New York and Massachusetts, I would watch both Ebay and Craigslist for at least a couple weeks to get an idea of what is available locally. I see a Tektronix 465 and 475 on Craigslist in your outer area which might be in good shape.

author: james_s
author_rank: Super Contributor
timestamp: March 14, 2017, 09:49:17 pm
content: Quote from: nctnico on March 14, 2017, 08:36:11 pmYeah and if you can get one for <$150 who cares? If it does eventually have a terminal fault you can part it out and make your money back and then some.I recently picked up a TDS784C, after buying new relays for the attenuators, a set of probes and some other bits and pieces I have about $800 invested but this is a 4 channel 1GHz 4GS/s color display scope loaded with all the options, deep memory, hard drive, advanced FFT, list price when new was over $35,000. It would cost me much more than I paid to get a modern instrument with equivalent capability.This is academic though, as like I said, for a beginner I would recommend starting out with an analog scope, the exception being if you plan to work with digital circuitry where you need to view stuff like SPI and I2C busses and other non-repetitive stuff. That's where a DSO really shines, but the learning curve is a bit steeper and there are a few pitfalls. Analog scope feels more "real", it doesn't have that abstraction layer between you and the signal, if that makes sense.

author: greg_gorrell
author_rank: Newbie
timestamp: March 15, 2017, 02:54:44 pm
content: Why no SPI or I2C on an analog scope? I would like to be able to reverse engineer with it too in the near future. I would think being able to determine if a camera is using either of those buses would be a feature I'd likely use. I am currently building a thermal imagine camera with a regular Arducam working over the I2C bus. I don't anticipate any problems to where I'd need to use the scope, but I do plan on playing around and viewing the waveforms for everything I can find find awhile until I get good at know what I am looking at and/or for. My experience with scopes is basically a semester in college haha.Again, thank you all so much. I kind of know only to look for some with a decent bandwidth but I have learned a ton from this thread and I at least have a good idea what I'm looking for now.

author: JPortici
author_rank: Super Contributor
timestamp: March 15, 2017, 03:02:49 pm
content: being analog, non storage, you need a constant stream of packets that are as simillar as possible (best if they are the same)otherwise once the trace fades you're out.forget about looking at start bits and things like that.youcandecode packets by hand. it's tedious but it's doable but you need a freeze frame to look at.

author: james_s
author_rank: Super Contributor
timestamp: March 15, 2017, 03:44:14 pm
content: You can capture SPI and I2C with a Bus Pirate or similar logic analyzer-ish device. A scope is more for signal integrity applications while logic analyzers are more about timing and data.

author: nfmax
author_rank: Super Contributor
timestamp: March 15, 2017, 03:59:14 pm
content: Quote from: JPortici on March 15, 2017, 03:02:49 pmUs old greybeards know that if you have a non-storage analogue scope, you canresetthe processor from the 'scope trigger out, and use delayed sweep to zoom in on a signal activity that occurs some (fixed) time after reset, repetitively. Of course in our day, we didn't have to worry about Linux taking 2 minutes to boot before anything interesting happens...

author: JPortici
author_rank: Super Contributor
timestamp: March 15, 2017, 04:39:39 pm
content: Quote from: nfmax on March 15, 2017, 03:59:14 pmthanks for the tip, this brownbeard loves ways to get around limitation. really open your mind

author: Gyro
author_rank: Super Contributor
timestamp: March 15, 2017, 04:51:02 pm
content: Quote from: james_s on March 15, 2017, 03:44:14 pmAgreed. Spend a very few $ on one of those 8 bit USB logic analysers off ebay to handle any micro data analysis needs, and then you can get on with deciding what scope you want!

author: james_s
author_rank: Super Contributor
timestamp: March 15, 2017, 07:43:34 pm
content: Quote from: nfmax on March 15, 2017, 03:59:14 pmNow that's a really clever idea that I wish I could say I'd thought of before, but I hadn't. I'll have to try that sometime just for fun.

author: nctnico
author_rank: Super Contributor
timestamp: March 15, 2017, 08:35:55 pm
content: Quote from: nfmax on March 15, 2017, 03:59:14 pmI'd like for those old days to stay in the pastI've spend way too much time staring at a screen decoding I2C or SPI messages by hand.

author: james_s
author_rank: Super Contributor
timestamp: March 15, 2017, 09:37:18 pm
content: Quote from: nctnico on March 15, 2017, 08:35:55 pmI'm glad to have modern tools but I like to stay sharp with the older methods. I tend to find myself working on things away from home and having to get by with whatever tools are around. It's handy to have old tricks filed away.