Idiot-proof Beginner Oscilloscope for Audio and TV repair and fun - Page 1
Forum section: electronics / testgear

author: achugh
author_rank: Contributor
timestamp: December 16, 2024, 04:21:14 am
content: Hi,I am new and have no idea how to properly use scopes. My Samsung Plasma TV from 12 years ago finally stopped working. I bought a new TV as this one is quiet old and gave good value for its money.Before I really throw this into dumpster, I thought it will be a really cool fun experiment to see if I can make it work again by taking some help from the community here.I have read and seen beginners like me make a fool of connecting the ground part of the probe incorrectly followed by blown scope. Is there any scope out there which is idiot-proof, budget friendly, is popular with this community so someone like me can get help learning it from your experience? To avoid this grounding mistake, I have read to use either an isolation transformer; these are big and bit expensive; or use differential probes. Not every model comes with these differential probes and these probes when factored into any decent scope makes the whole kit an investment.So do you have any recommendation for someone like me? For audio, video (mainly TV) repair which scope do you recommend and what features I should be looking into? Like, do I need UART decoder or MSO type unit with some signal generators in them, 100 MHz or 200 MHz frequency, ability to save data on USB drive or card or connect to computer etc.As the sticky post says, there must have been lots of similar posts like this already. I hope the community can help one more time to share their experience as technology evolves and hence the pricing which changes the recommendations all the time.Thanks in advance for your help.

author: tatel
author_rank: Frequent Contributor
timestamp: December 16, 2024, 06:57:41 am
content: This one is dirty cheap, it would be enough to begin fooling around, after that you'll know quite a bit more and could make a much more informed purchase of a better model:https://www.eevblog.com/forum/testgear/new-toy()-scope-dso154pro-1ch-claimed-40mss/msg4531274/#msg4531274Here you have a list of cheap portable oscilloscopes:https://www.eevblog.com/forum/testgear/portable-oscilloscopes-list/msg5194335/#msg5194335You could also get one of these Owon HDS devices, these are quite a bit more serious:https://www.eevblog.com/forum/testgear/owon-hds-200-handheld-oscilloscope-w-builtin-dmmawg/msg3451228/#msg3451228But if you just have too much money, one of the new siglent HD models would be the way to go:https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293741/#msg5293741

author: ebastler
author_rank: Super Contributor
timestamp: December 16, 2024, 07:01:34 am
content: You don't write explicitly about your level of electronics knowledge in general. But given the fact that you have no experience with oscilloscopes, I will assume that the same applies to electronics design and repair overall.If that is the case, learning how to use the oscilloscope is only a small part of the task ahead. And trying to repair a plasma TV is probably not the best starting point, given that it is not only mains-powered but uses even higher voltages inside, and that it uses highly integrated, complex and somewhat uncommon digital ICs.If you are really interested in digging into this, one of the current 4-channel, 12-bit-ADC scopes would be a good choice. The 12 bit input section lets you look at analog signals in detail; the four channels and built-in decoders let you check serial buses like I²C and SPI. (Which are very commonly used, not only in consumer devices like TVs but also in beginner-friendly projects built around Arduinos and the like.)The Rigol DHO804 is probably a bit more beginner-friendly than its counterpart from Siglent (SDS804X HD) due to its UI. But still, be prepared for an extended learning curve!Edit: Oh -- and donotbuy a battery-powered scope as a way to avoid the grounding "problem"!! Measuring on mains-powered devices with a scope that is not properly grounded can be very dangerous, especially for a beginner.Edit²: Your earlier posts show that you have dabbled in electronics repairs a bit, know about the basic components, and have sustained the interest in electronics for at least the two years you have been on this forum, probably longer before that. That's great! Makes me feel better about the 12-bit/4-channel recommendation. As indicated by tatel, there are cheaper scopes. But given your sustained interest, I think starting with a "real" scope from Siglent or Rigol is warranted (if they fit your budget).

author: axantas
author_rank: Regular Contributor
timestamp: December 16, 2024, 09:40:50 am
content: Regarding the proper grounding and not to blow up your oscilloscope or other equipment, there is an excellent video from Dave here:

author: Aldo22
author_rank: Super Contributor
timestamp: December 16, 2024, 09:45:35 am
content: I don't believe that there is an "idiot-proof" scope.It's like bicycles: If you hit the wall, it hurts, no matter what bike you have.There are simply cheap scopes with a manageable range of functions.As a first scope, this is quite OK and mistakes are not that expensive.For example, theZEEWEII DSO1C81Once you have understood the basics, you can buy a "real" scope (Siglent, Rigol), a model that meets your needs (which you obviously don't know yet).I wouldn't buy a "half-good" scope as a first scope.Start with a really cheap one and then buy a good one.

author: Atlan
author_rank: Frequent Contributor
timestamp: December 16, 2024, 10:51:01 am
content: Buy a 1013D, it has its faults, the worst being low sensitivity. But it should be possible to repair him if you hurt him. In addition, a touch screen and quick start. Simple control.Or just buy something that was recommended to you - a 4-channel adult oscilloscope, you will definitely not make a mistake.Many people use small portable simple oscilloscopes for a quick look at the signal when solving simple tasks. So they have 2 oscilloscopes.

author: Sorama
author_rank: Frequent Contributor
timestamp: December 16, 2024, 11:26:17 am
content: why oh why do people think you can do a specific job (electronics repair) without having the knowledge to do so?did we all become EE for nothing?(it's that time of the year one might become philosophical)

author: ebastler
author_rank: Super Contributor
timestamp: December 16, 2024, 12:54:11 pm
content: Quote from: Sorama on December 16, 2024, 11:26:17 am

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 16, 2024, 02:24:39 pm
content: You have to start somewhere but I don't think a plasma TV is the best place. Learning to repair is good but you can't approach it that way. You have to learn electronic fundamentals first. The repair knowledge comes later. Start with ohms law. Once you understand why current flows, you'll start to understand how not to explode your test equipment with bad hook-ups.

author: achugh
author_rank: Contributor
timestamp: December 17, 2024, 03:26:37 am
content: As a background, I have a 4 years Bachelor's degree in Electronics and Telecommunication Engineering. I got this degree almost 30 years ago. I never pursued this field and this degree as I got into computer programming and that is what I made my career with.I understand and remember the very basics of things. A quick refresher article or a video is good enough for me to jog my memory. Some pointers from seasoned folks here goes a long way.In my college times, the scopes in our labs were always busted by classmates making these foolish mistakes of not grounding things properly so I never learned to use them.If I count all of my repairs so far, they will be in single digit. All of them have come down to some blown cap in the power supply circuit or a bulged caps that can be visually spotted for a quick repair.My Samsung Plasma TV had a small spark and a bit of smell after which it never worked. When I try to turn it on, the standby light turns on. If I try to turn on the TV, I get no picture. I believe the power unit in it is working and something else got burnt.I also have two electrical heating pads with a single digit display. One heating pad works and the other gives an error. If I swap the controller cable to the other pad, the other pad works. This tell me that the pad controller cable with its control unit has gone bad. I would like to make an attempt to repair it.I also have an Iron to iron my clothes. The auto shutoff on this iron no loner works. It will be great if I can repair its auto shutoff.I am also having some slight hum in my two identical subwoofers using Dayton Audio SA1000 amps. I would like to find the root cause of it and fix this hum. I am asking for help about this hum inhttps://www.eevblog.com/forum/repair/repair-help-dayton-audio-sa1000-subwoofer-amp-emitting-ac-hum/post on the forum.Its things like these is what I am interested in learning to fix. Most of them have to do with power which is why I asked for an Idiot-proof scope.I saw the Siglent scopes as they seem to be popular here. The differential voltage probes are almost the price of a scope. It took my heart out seeing MSRP on their website just for these differential probes.I also saw that these Siglent scopes can be hacked to enable additional features like buying a 100MHz scope and making it 200MHz. Although I did not understand why would anyone do that since the test probe is still rated for 100MHz unless one goes out and buys the 200MHz rated probe for the scope to work as well. These probes are not cheap and I have not done enough research to see if it is best to get the 200MHz rated scope in the first place so you get the matching probe to go along with it.I call myself beginner even though I have the degree because I literally forgot most or all of it. All I can say is that the learning curve will not be steep but I will need to learn from this community or doing my own research online.Regarding some of the cheapest Chinese scopes, I went through all the 4 pages ofhttps://www.eevblog.com/forum/beginners/recommend-budget-oscilloscope-please/post. This post links out tohttps://www.eevblog.com/forum/beginners/what-an-oscilloscope-recommended-for-a-woman-passionate-about-electronics/msg3100087post which I have not started reading yet as it is almost 40 pages and it takes time to read so much information as well as digest it.I thought I can have my own post and get information relevant for me from you all.Thanks in advance for the information already shared as well as any further information anyone will share here to help me out.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 17, 2024, 04:40:13 am
content: Differential probes are uncommon. Don't have one and don't know anybody that does. There are high voltage one and high frequency ones, aimed at different applications. The usual thing for lower frequencies is to use two channels, invert one and subtract them. Result is differential signal. Still need to ground to something, so it's good to have an isolation transformer for things that don't have a transformer. Things without transformers are, IMHO, best tossed and replaced until you really know what you're doing. IMO. transformer-less power gadgets are absolutely not the place to start learning, even with some background. Siglent thinks a great application for their HV diff probes is 3-phase power. I've been at this for many years and leave that stuff to specialists trained in arc flash. Too easy to make a mistake.As for probe bandwidth, it depends on what you're trying to see, but a lot of RF work is 50 ohms. The Siglent lower end scopes don't have a 50 ohm input, but you just use a common 50 ohm terminator and hook up your coax; no scope probe even used and you get the full BW of the scope. Any fast probe is going to be X10 and trying to see some little fast signal is often difficult. Worse, many points you might like to probe will be loaded down by the capacitance of even a good X10 probe. That's why they make (expensive) active probes, including the differential ones. Or, there are some DIY versions.

author: Smokey
author_rank: Super Contributor
timestamp: December 17, 2024, 04:55:36 am
content: If you are looking to troubleshoot a modern TV all you need is a multimeter. Measure the power supply voltages. If one of the power supplies isn't working, replace the power supply.Apart from that, there is essentially nothing you will be realistically repairing.

author: Fungus
author_rank: Super Contributor
timestamp: December 17, 2024, 06:52:37 am
content: Do you own anything else? eg. Multimeter?What's the budget?

author: tatel
author_rank: Frequent Contributor
timestamp: December 17, 2024, 07:15:00 am
content: I first got a benchtop DSO, then I got dirty cheap DSO154Pro to recklessly fool around low voltage, battery powered devices. That allowed me to learn faster about the basics than my fancy DSO with its thick manual and not-so-cheap price tag. Then I got into things connected to mains and got a cheap second-hand old analog oscilloscope for that. Should I be low on caffeine and blow it, well, that would be cheap, and they can do that pseudo-differential measurement mentioned by Conrad Hoffmann. I'm not aware of any cheap portable oscilloscope able to do that pseudo-differential measurement. Ideally you'd be using an isolation transformer to float the DUT before doing that.However there are quite a bunch of threads about the controversy "isolation transformer vs differential probe". Main thing being, isolation transformer will nullify any protecting device in your electrical installation. No doubt others will give you better advice than me on that. Personally I decided to bit the bullet and get a Micsig relatively cheap differential probe. I could also get an isolation transformer in the future. You'll have to make your mind about this.Only the "usual" probes are cheap. If you get, say, a 200 MHz rated oscilloscope and use 200 MHz rated probes with it, you'll be under 200 MHz bandwidth. To avoid that, you'll need, say, 300-350 Mhz probes, and that wouldn't be so cheap. There are OEMs selling probes rated for some bandwidth, but able to do more, so these would be good. Again, others here will be able to give better advice than me. But main point here is, probes are expensive, not just the differential ones, unless they are the usual run-of-the-mill ones.If you need to look into decoding I2C or SPI, there are cheap -and not-so-cheap- devices that will allow you to do that. I got a DSLogic clone from AliExpress. A dirty cheap Salae clone didn't work for me, it turned out to be defective. Perhaps to be expected after that $8 price. Anyway, having a working logic analyzer, you wouldn't need an oscilloscope able to do any decoding, so an old, cheap, two-channels analog oscilloscope would be good enough to do all you want.Problem with old analog scopes is "are they working good?". If not, usually you need an oscilloscope to repair an oscilloscope.Last, since you are not the usual noob and have experience programming computers, perhaps you could run into some of these -rather rare- cases where you would really need a mixed-signal oscilloscope. The problem with these is, many times, when you use the digital channels, features get halved or even worse. Siglent's SDS1104X-E would be an example of that. But not the only one. You could do a search on this forum and find posts about it. You should look for owner advice if you are interested in any MSO. It wouldn't be an entry-level one, of course, if you want it to work OK.Perhaps I'm not really helping, I fear, But it is what it is. You'd need to think about this and decide which way is your way, and go for it. Fortunately there's a lot of people here able to answer any questions you could ask, way better than me.Good luck

author: J-R
author_rank: Super Contributor
timestamp: December 17, 2024, 09:38:42 am
content: There are multiple methods for learning as a hobbyist. One path I like personally is fixing test equipment because then you can use it on the bench. I agree the plasma TV is a poor place to start, but also you CAN get pretty far by just testing passive components with the TV completely unplugged. Look out for charged capacitors! If you must tinker with high voltages, be sure to wear safety glasses, cover exposed skin, wear gloves, rubber shoes, have someone watch you work, etc...BUT, THERE IS NO ABSOLUTE REQUIREMENT for an isolation transformer or isolated probe in this situation. Simply completely remove the ground clips from the oscilloscope probes on two channels, set up the math function and you're good to go for making differential measurements, assuming you have the correct probes for the voltages you'll encounter (100X for example).Video demonstration:If for some reason you still want all that stuff:I'd suggest a high voltage differential probe because that can cover two use cases at once: high voltages and differential measurements. I got a good deal a couple years back on the Micsig DP20003 which is rated to 5,600V.For an isolation transformer, I picked up the Tripp Lite IS250 which I modified to make it truly isolated (out of the box the output neutral and ground are not isolated). Using this requires careful attention.Another option for isolation is a UPS (battery backup). I suggest a pure sine wave model. You simply unplug it from the wall when you want isolation...

author: tggzzz
author_rank: Super Contributor
timestamp: December 17, 2024, 10:35:59 am
content: Quote from: achugh on December 17, 2024, 03:26:37 amTo fix those, I suggest using a voltmeter, your eyes, and understanding. I don't think a scope will add anything.QuoteAgain, I don't think a scope will help you there. The causes of hum are normally cured by understanding possible causes plus trial and error. (I haven't read your other thread.QuoteThere can never be any such thing, since idiots are so damn ingenious. Seriously.Example from my past:https://www.eevblog.com/forum/projects/how-can-i-protect-my-circuit-from-clueless-plebs/msg1392190/#msg1392190QuoteYes. Deal with it.For the avoidance of doubt,never ever float a scope, using two channels with invert-and-add doesn't make it safe, and isolation transformers can make thingsmoredangerous.QuoteFor the problems you have mentioned, you don't need 200MHz. 10MHz is more than sufficient, and 100kHz is probably sufficient.Plus an HV differential probe, of course.QuoteProbing is an important topic, doubly so when doing anything "near" mains power.To avoid a lot of grief, see the references athttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: Aldo22
author_rank: Super Contributor
timestamp: December 17, 2024, 02:15:19 pm
content: Quote from: J-R on December 17, 2024, 09:38:42 amThank you, I didn't know that.I always wondered what “invert” could be good for.Just tested it on my cheap scope.It works. There is no automatic measurement for the math channel, but with the “track” cursor it still measures it automatically.Quote from: tggzzz on December 17, 2024, 10:35:59 amCould you explain this?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 17, 2024, 03:43:34 pm
content: I am kinda with Tatel on this one.....If you just want a basic scope, try to go to a Hamfest and see if they have an old CRT scope. They are incredibly cheap in the US.Tek 465 go for less than $100 (100MHz). I just saw a nice one a few months ago. Lesser scopes like 20 MHz can be bought for $20.You can plug it in and see if it makes a trace and test with the cal connection.The cheap Chinese probes are very good, in my experience also. Just make sure the input impedance matches the scope.Look in the ARRL list for one in your neighborhood.http://arrl.org/hamfests-and-conventions-calendarI am not saying that old scopes are preferable to new digital ones. I use an Agilent 58420 digital. The new scopes do much more than just being scopes.But it is a good way to refresh your knowledge base and have some fun.Just one amateur's opinion. Not an EE.I do not think that most values given ( like voltage) on DSOs are as accurate as values given by good other test equipment. However in most repair cases they are more than adequate.

author: tggzzz
author_rank: Super Contributor
timestamp: December 17, 2024, 04:19:38 pm
content: Quote from: Aldo22 on December 17, 2024, 02:15:19 pmI'm not going to waste my time creating a worse explanation than the references I noted.

author: tggzzz
author_rank: Super Contributor
timestamp: December 17, 2024, 04:29:40 pm
content: Quote from: Wallace Gasiewicz on December 17, 2024, 03:43:34 pmScopes' principal use is to see a waveform's shape. Vertical accuracy is often +-2-3%, i.e. worse than a moving coil meter.They bring other measurement problems, and are often not an appropriate tool.

author: Fungus
author_rank: Super Contributor
timestamp: December 17, 2024, 04:49:49 pm
content: Quote from: achugh on December 16, 2024, 04:21:14 amThere's really nothing you can fix inside them unless it's the power supply. Everything is now "order a replacement board".Measure the voltages (there's often labelled test points). If they're correct then trash it.If they're wrong, look for a blown fuse. If the fuse is OK look for swollen electrolytic capacitors. If you can't see any, trash it.

author: KungFuJosh
author_rank: Super Contributor
timestamp: December 17, 2024, 05:03:52 pm
content: Quote from: Aldo22 on December 17, 2024, 02:15:19 pmThe simplest explanation is that if the scope isn't grounded, you could potentially become the path to ground.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 17, 2024, 05:40:04 pm
content: I avoid being a path to ground; it's usually painful or worse. The scope will also have some common mode limits so just connecting two probes with no ground is a bit iffy. In that case the power ground becomes the ground, which is a noisy and, if you're working on some two-wire power device, like a TV, things end up unreferenced. Probably best to just stick with a DVM. I've worked on a couple TVs and quickly concluded that a new TV was cheaper than my time to fix, or maybe not fix, the old one. They're also too big for my bench.

author: Fungus
author_rank: Super Contributor
timestamp: December 17, 2024, 05:46:21 pm
content: Quote from: Aldo22 on December 17, 2024, 02:15:19 pmIf you connect a probe ground clip to a live wire then all the exposed bits of metal on the 'scope also become live and you can easily touch them.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 17, 2024, 06:05:52 pm
content: Quote from: Aldo22 on December 17, 2024, 02:15:19 pmThe reason not to float a scope has been explained, but the isolation transformer hasn't.It's because they render upstream RCD/RCBO/GFCI devices ineffective.The best scope to probe things like this is an old Philips/Fluke scopemeter, or a Tek THS7xx series.There is no "idiot proof", whatever TE you use, you will be probing dangerous voltages, and should always bear that in mind. Scopemeters and other brand battery scopesthat have fully plastic bodies and BNC connectorsare designed with these uses in mind, and are more difficult (butnotimpossible) to damage than bench scopes.You can find them ranging in price from $100 to $300 quite easily, but bear in mind the Philips and older Flukes are very prone to embrittlement of the casing plastic. Tek THS scopes have individually isolated channels, useful if you need to probe power rails that don't/shouldn't share a common ground.

author: NE666
author_rank: Frequent Contributor
timestamp: December 17, 2024, 07:23:20 pm
content: Quote from: AVGresponding on December 17, 2024, 06:05:52 pmI'll offer a +1 for that suggestion. Whenever I've needed to diagnose the operation of a suspect SMPS, my old Fluke 867B "Graphical Multimeter' has been sufficient. It samples at just 5M points/sec, and manages just 4 screen updates per second. Still tells me everything I need to know but it does so whilst also being CATIII rated at 1000v and not electrically grounded. And that's Fluke CATIII, not ali express CATIII.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: December 17, 2024, 11:47:44 pm
content: Hello achugh,All of the explanations and hints given by @tggzzz, @KungFuJosh, @Conrad Hoffman, @Fungus, @AVGresponding and @NE666 are wise and of great value.If you need to probe on live circuits and really want to use an oscilloscope, today's safest method is using :1) a truly isolated scopeor2) differential probes + non isolated scope.Or use a good CAT III multimeter.Everything else is much less safe, or worse, it gives you a false sense of safety.You may read this thread :When (where) is it safe to measure with oscilloscopeand follow the links in the different posts.

author: J-R
author_rank: Super Contributor
timestamp: December 19, 2024, 06:41:45 am
content: I'm all for buying new gear, but perhaps knowledge is the more powerful asset...

author: wasedadoc
author_rank: Super Contributor
timestamp: December 19, 2024, 10:15:31 am
content: Quote from: J-R on December 19, 2024, 06:41:45 amJust as writing it on a whizzo word processor does not guarantee your novel will be a best seller.

author: Aldo22
author_rank: Super Contributor
timestamp: December 19, 2024, 02:32:41 pm
content: Thanks to everyone who has answered my questionhere.My question was a bit vague. I was in the context of “two channels with invert-and-add” and I should have been more specific. My point was not to float the scope.Now I've played with that a bit.First of all, on a DSO, Math: subtraction is probably easier than invert+add. That amounts to the same thing, doesn't it?Then I played with my FY3200. It doesn't come with a 3-wire cable. I made one myself, whereby I can switch the PE on/off.If it is grounded, then the 2nd channel is of course without signal. So this method is useless.If it is not grounded, then there is so much voltage on it (90Vrms) that you can hardly see the signal.However, it works really well with a battery-powered signal generator.

author: achugh
author_rank: Contributor
timestamp: December 27, 2024, 12:02:00 am
content: Thank you AVGresponding for sharing Tek THS7xx series.Thank you tggzzz for responding to me specific questions. If you have some time, can you please look into my subwoofer amp humming issue athttps://www.eevblog.com/forum/repair/repair-help-dayton-audio-sa1000-subwoofer-amp-emitting-ac-hum/and share some pointers for me?Thank you to all who have contributed so far. I am reading all the valuable and important information shared. It will take me few days to go through the plethora of information already shared.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 27, 2024, 01:42:25 am
content: Also read the specs of your probes, there is a voltage derating curve with frequency that's quite surprising.I once thought I'd tool around inside trashed TVs for fun, I have a 100X 120MHz probe rated for 1.5KV (P6009), so no problem right?I decided to probe some HV point in the TV and I heard a squeal and a pop and saw smoke come out the compensation box of the probe.Hm, that high voltage rating goes down real fast after 1 MHz or so.I fixed the probe but my pride is still hurt.I leave TVs in the trash now. (Unless it's an awesome CRT set)