Need a scope, Is vertical sensitivity important? - Page 1
Forum section: electronics / testgear

author: deezdrama
author_rank: Contributor
timestamp: December 07, 2022, 05:03:02 pm
content: Ive been doing maintenance on dozens of expensive 15kHz crt tv's and pro monitors... Usually just a deflection circuit capacitor replacement brings things back to life after I test the caps for bad esr and replacing the suspect capacitors but am working on a sony pvm 20m2u that worked fine after a recap for about 30 minutes before another component went out and caused image unstableness and a loss of vertical sync.I reflowed the board, tested all caps again, checked that no resistors had failed open, checked diodes for voltage drop, replaced sync ic chip.... On and on....I need a scope!It will be my first scope and will learn to use a scope on it.I dont want to have to spend $500+ if I dont have to.Ive seen alot of great reviews and alot of bad reviews on the Fnirsi-1014d which is around $150.https://www.walmart.com/ip/FNIRSI-1014D-7-inch-Signal-Generator-LCD-2-In-1-Dual-Channel-Input-Desktop-Oscilloscope/278754013?athcpid=278754013&athpgid=AthenaItempage&athcgid=null&athznid=utic&athieid=v0&athstid=CS020&athguid=Vk0iS9SzrNvZuBUN1E4nL1W3L9eGhrc9bGZ_&athancid=null&athena=true&athbdg=L1600My biggest concern with it is with Vertical sensitivity only going down to 50 mV/div.Ive read this makes reading signals under 1v spotty at best.Im not even sure what specs I need in a scope. Most of the high voltages in a crt are easy to troubleshoot without a scope..... Its all the rgb and sync level driven IC's on the board that I need to troubleshoot and alot of those are under 1Vpp so I dont want to end up with a scope thats not good for troubleshooting these areas on the chassis boards I work on.I really just need a scope to probe the monitors chassis boards IC's to compare results against the service manual.Theres been some buzz on this little battery powered 200kHz scope as being a good buy for checking rgb and sync levels but again, not sure of its vertical sensitivity range or if it would suffice for basic testing against the service manual of these crt monitors?Mini Digital Oscilloscope, Leolov Oscilloscope Kit Support AUTO, PWM, One-Button Reset Button, Firmware Update, 2.5MS/s Sampling Rate, 200KHz Bandwidth, 2.4 Inch LCD Display with 10X Probehttps://a.co/d/5x428AwId love a rigol but the highest I could swing right now is around $300 on something like this siglentSiglent Technologies SDS1202X-E 200 mhz Digital Oscilloscope 2 Channels, Greyhttps://a.co/d/iJGNm8SIts claims .5mv vertical sensitivityIm not even sure if these vertical sensitivity specs are important for what I need. I just need a cheap scope to learn on and to test/troubleshoot these old crt monitors and compare waveforms vs the ones posted in the service manual to pinpoint problem circuits in the chassis boards.Any help is appreciated!

author: Pilatus
author_rank: Contributor
timestamp: December 07, 2022, 05:10:11 pm
content: For the kind of work you do, I would think that a good analog scope would fit your present requirments and give you a better understanding of what a scope can offer. Used ones can be had on ebay for $100 or so.In general vertical sensitivity and bandwidth are important parameters, however you need to define what you will be using it for. For CRT type of work, audio etc, 5 mV should be fine.Others will definitely be chiming in here soon and likely offer you more refined feedback.

author: pcprogrammer
author_rank: Super Contributor
timestamp: December 07, 2022, 05:20:09 pm
content: There is the Hantek DSO2C10 which is more sensitive then the FNIRSI-1014D, but is does have several bugs in the software. It is in similar price range though, and most of the C units are shipped with the AWG components installed. A simple upgrade can be done to turn it into a DSO2D15.The FNIRSI only does 200MSa/s per channel, where the Hantek can do 1 channel on 1GSa/s or 2 channels on 500MSa/s. It also has way more sample memory. The FNIRSI has only ~30MHz bandwidth where the Hantek has 150MHz.Both units have been dissected thoroughly here on the forum.But to be honest the best advice would be to squeeze the budget a bit more and try to reach for either the cheapest Rigol or Siglent scope. You will get something better with them than the FNIRSI or Hantek, or any of these other cheap brands or low sample rate, small screen toys.

author: bdunham7
author_rank: Super Contributor
timestamp: December 07, 2022, 05:34:01 pm
content: In general, to avoid frustration and wasted money, just avoid junk. I'll leave it to others to define 'junk', but I'm pretty sure FNIRSI and Yeapook fit the description.When you use a scope you typically want to use 10X and even 100X probes to avoid circuit loading as well as looking at high voltages. So vertical sensitivity and low noise are important even if you aren't looking at very small signals. 5mV/div would be the very worst that I could accept, 2mV/div was a sort of common spec for analog CROs and 0.5mV/div is what a decent modern DSO will give you.

author: deezdrama
author_rank: Contributor
timestamp: December 07, 2022, 06:43:45 pm
content: Thanks guys! Ill skip the cheapies, I just watched Kerry Wongs teardown and yeah... Ill avoid those.Any thoughts on this siglent?Siglent Technologies SDS1202X-E 200 mhz Digital Oscilloscope 2 Channels, Greyhttps://a.co/d/6KV85BKAlso....Im not opposed to looking for an older rigol or siglent model used on ebay unless theres concerns about buying used, any particularly decent older models to look for that might fall in the sub $300 used range?Thanks for the help...much appreciated!

author: mwb1100
author_rank: Frequent Contributor
timestamp: December 07, 2022, 06:50:16 pm
content: You might also consider the SDS1052DL+, available on Amazon US for about $250 at the moment:-https://www.amazon.com/Siglent-Technologies-SDS1052DL-Digital-Oscilloscope/dp/B01J16NV54It's only 50MHz, but maybe it's enough for what you need? It's not clear to me how hackable it is, but there's some indication:-https://www.eevblog.com/forum/testgear/siglentsds1052dlsds1102cmlhack/msg2731812/#msg2731812I think it's the lowest-end of what Siglent currently offers for bench scopes.But if you can stretch your budget to the SDS1202X-E - that's a far superior oscilloscope than the SDS1052DL+

author: tautech
author_rank: Super Contributor
timestamp: December 07, 2022, 07:29:26 pm
content: Quote from: mwb1100 on December 07, 2022, 06:50:16 pm100% endorse all of this ^SDS1052DL+ will be the easier to learn with however as one advances it's minimal feature set might not meet future requirements whereas the 2ch X-E will certainly be a better match as skills grow.deezdramaLook up Defpom on YouTube as he reviewed a DL+ a couple weeks back for us.

author: deezdrama
author_rank: Contributor
timestamp: December 07, 2022, 09:44:37 pm
content: Quote from: tautech on December 07, 2022, 07:29:26 pmThanks guys this helps alot. I grabbed an open box 1052DL+ on amazon for $170.... Hopefully its not missing the probe or anything.Are these possible to run off a battery pack?

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2022, 09:51:13 pm
content: Fnirsi lies about the specs, I lump their products into the category of toys. You don't have to spend $500, the Siglent SDS1202X-E is $339, and the Rigol DS1202Z-E is only $299, both of these are "real" scopes from reputable brands. Or you could look around and see if someone will give you a deal on an old analog scope, those work fine for the sort of signals you're likely to find in a CRT monitor, it's what the service manuals for the monitors would assume you were using.

author: electr_peter
author_rank: Unknown
timestamp: December 07, 2022, 09:56:18 pm
content: HiFNIRSI is not a "scope" for your needs, it is a toy (many bugs, incorrect implementation, very limiting specs, bad UI), not recommended.If you need something portable and small,OWON HDS 200 Handheld Oscilloscopemay fit your needs (fits in a your budget). It is a scope (a bit limited, but 100x better than FNIRSI) and DMM in one.Other portable scopes (like Micsig and offerings from Siglent and others) are over your budget.Siglent mentioned above is good scope for limited budget.

author: tautech
author_rank: Super Contributor
timestamp: December 07, 2022, 10:02:09 pm
content: Quote from: deezdrama on December 07, 2022, 09:44:37 pmThey can be as they are SMPS powered but unknown is the DC requirement for the SMPS to start running.Running scopes from a DC supply breaks the functionality of the Line trigger.Soon I'll have a spare SMPS PSU that fits my SDS1104X-E and finding its DC start requirement will be one of our Christmas projects.

author: mwb1100
author_rank: Frequent Contributor
timestamp: December 07, 2022, 10:03:16 pm
content: Quote from: deezdrama on December 07, 2022, 09:44:37 pmNice! I didn't notice that offer.If probes are missing you can get a couple 100MHz probes for $20 or less. It would still be a pretty nice deal in my opinion.

author: Martin72
author_rank: Super Contributor
timestamp: December 07, 2022, 10:13:47 pm
content: Quote from: deezdrama on December 07, 2022, 05:03:02 pmWell, this is....remarkable.Doing repairs on TVs without scope is like driving a car with eyes closed.Having a scope is a must, multimeters "telling" you nearly nothing.Your planned budget is very small, but yes, forget the fnirsi/yeapook/hantek crap, at last for safety reasons.When it´s mainly for repairs on old CRTs you wouldn´t really need a DSO, nice to have but a good old analog scope would fulfill your needs also.The rest of your budget I would spend for a galvanic isolated transformer (or a differential probe), because chassis gnd of the TVs is NOT earthed gnd and could have high potential that will flow to earthed gnd when you use the scope( because scope gnd is earthed).A 500VA transformer should be enough for every kind of CRT.So a used analog scope plus transformer or when budget can be stretched, a rigol or siglent DSO plus transformer.Or at least a differential probe.

author: deezdrama
author_rank: Contributor
timestamp: December 07, 2022, 11:09:56 pm
content: Quote from: Martin72 on December 07, 2022, 10:13:47 pmI worked on cars my whole life untill getting a decent scanner 6 or 7 years ago, but yeah your right it usually involved alot of educated guesses and throwing parts at things untill they ran lol.With crt's ive found 9 out of 10 times its a bad/dry electrolytic capacitor in the deflection circuit that causes issues or protection shutdown of high voltage from the flyback transformer...... But...... That 1 out 10 i definitely been shotgunning at blind lolI ended up ordering a Siglent SDS1052DL+, found an open box for $170 so jumped on it.Sounds like it will be decent to learn on and if I need to upgrade in a year or so I can probably recover most of the $170 spent.Those cheap aliexpress scopes had one thing that appealed to me.... Being battery powered and floating from the device being worked on. Ive read mention a ton of times about needing an isolation transformer but never looked into it a whole lot. So this is wise to use 100% of the time?I thought I read it was vital for pre 1980s crt's that had live chassis..... All the monitors I work on are 1990 or newer, is it still vital to use isolation? I didnt plan to have to buy an isolation transformer as well, maybe I should of spent a little more on a decent portable scope?

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2022, 11:26:11 pm
content: I repaired CRT TVs and monitors for many years without a scope, most of the time I found shorted transistors, bad capacitors, sometimes an open resistor, a scope does make things easier though.Don't forget to watch Dave's video on how to not blow up your scope. Many TV sets use a hot chassis design, most monitors (except older arcade monitors) don't but the power supply section will.

author: nctnico
author_rank: Super Contributor
timestamp: December 07, 2022, 11:29:14 pm
content: Stay clear from isolation transformers. Better get a high voltage differential probe and a 1:100 passive probe. Back in the old days (>20 years ago) I have repaired lots of CRT monitors myself and a simple analog scope has always been enough to figure out what was going on. A 'hot chassis' is something from a very distant past but it is a good idea to investigate which part of the board is connected to mains and which part isn't. Typically this is made very clear on the board. Nowadays a simple DSO will do just fine. Only 'problem' I find with modern DSOs is that they typically don't have a 20V/div setting.If you want a neat portable DSO, then make sure to look at the ones from MicSig. They also have special automotive models.

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2022, 11:35:04 pm
content: Quote from: nctnico on December 07, 2022, 11:29:14 pmHot chassis TVs were made right up into the end of the CRT era, mostly cheap sets, a good clue is they have no headphone jack. Even on sets that have a proper SMPS it is often integrated into the main board so there will still be live earth referenced stuff in the vicinity.

author: tautech
author_rank: Super Contributor
timestamp: December 08, 2022, 01:18:44 am
content: Quote from: deezdrama on December 07, 2022, 09:44:37 pmIt should come with a pair of PB470 switchable 1x/10x probes as outlined in the Siglent probe listing:https://siglentna.com/wp-content/uploads/dlm_uploads/2022/08/Probe_List_008102022.pdfAlso check it has the latest firmware installed and update from here as required:https://int.siglent.com/download/firmwares/?ProId=42Btw, you nicely nabbed a good saving at that price of over $ 100 !

author: deezdrama
author_rank: Contributor
timestamp: December 08, 2022, 01:24:27 am
content: Quote from: tautech on December 08, 2022, 01:18:44 amThanks for the linksIll update when I get it. Yeah i seen it that cheap and jumped on it, hell thats the same price as the aliexpress toy scope i thought about getting lol

author: deezdrama
author_rank: Contributor
timestamp: December 10, 2022, 07:22:25 pm
content: Just got the scope in.No box but looks to be complete.Whats the best signal sources I can use to learn on this with?Should I get a cheap signal generator?

author: james_s
author_rank: Super Contributor
timestamp: December 10, 2022, 07:32:15 pm
content: Looks like a fun new toy.A signal generator is handy but you can also build something. Do you have a breadboard and some parts? Lots of oscillators can be built around transistors or op amps. An arduino or other microcontroller can easily give you square waves and single shot pulses. Random electronic equipment has various signals in it, though I do recommend sticking to battery powered stuff until you know what you're doing. Anything that has an external power supply that produces low voltage DC can be lumped in with battery powered stuff. Just stay out of anything that has a line voltage power cord going into ir.Watch Dave's video on how to not blow up your oscilloscope, and also check that the probes are set to 10X and leave them that way, there is rarely a reason to use the 1X setting and it increases the risk of damaging the scope.

author: deezdrama
author_rank: Contributor
timestamp: December 10, 2022, 07:56:55 pm
content: Quote from: james_s on December 10, 2022, 07:32:15 pmThanks for the suggestions, I do have a box of audrinos somewhere and breadboards, ill have to see what I can throw together.Ive watched daves video and alot on the same topic, and read alot of articles and its left me confused. Seems like back in the day everyone suggested isolating the device being scoped and now they dont.Going to research it some more as ill ultimately end up using the scope to test crt monitor circuits and IC's.The monitors have seperate power boards but not sure if the chassis board is connected to earth ground. Ill have to test for continuity between earth ground and the chassis board and how to safely probe these circuits.Alot to learn

author: tautech
author_rank: Super Contributor
timestamp: December 10, 2022, 08:06:22 pm
content: Quote from: deezdrama on December 10, 2022, 07:22:25 pmFor now just setup the probes correctly, that is assign them to each channel with the colored rings and with them and the input attenuation set to 10x compensate the probes to get a symmetrical square wave.Use ~200us timebase for that then start fiddling with timebase and vertical sensitivity to get a feel for basic operation after which go looking through the menus at the various features, even trying some to get the feel for them. Try engaging some measurements instead of needing to count graticules and tune this setup so to be able to bring them back with just a toggle of the Measure button.Practice getting screenshots too so you can come here for advice with a picture, hopefully displaying an appropriate menu that shows settings.You will at some point want a signal source however as a right of passage into electronics everyone makes a 555 timer or a Hex inverter oscillator both of which can be done with combinations of R and C.While this thread is not with the same model DSO there is a pile of wealth to be had from it as we worked through the capabilities of Charlotte's new Siglent:https://www.eevblog.com/forum/beginners/what-an-oscilloscope-recommended-for-a-woman-passionate-about-electronics/msg3104228/#msg3104228Have fun and try to get to a point of knowing what form a waveform will take before you even put a probe on it.A little hard for sure with limited electronics experience but it will help you on the road to understanding electronic building blocks even if it's only at a conceptual level.Enjoy your new eyes into a new and wonderful world.

author: deezdrama
author_rank: Contributor
timestamp: December 12, 2022, 01:05:43 am
content: So I cleaned up my bench a little bit and made a home for the scope, got the probes color coded, set to 10x and compensated.Im wondering if the little green "ready" indicator is supposed to be flickering between ready and auto like this?https://youtube.com/shorts/8EAJWdZeGcY?feature=share

author: tautech
author_rank: Super Contributor
timestamp: December 12, 2022, 02:09:43 am
content: Quote from: deezdrama on December 12, 2022, 01:05:43 amQuoteNormal in Auto triggering mode.Remove probe from Comp output then switch to Single trigger mode and then reconnect to see what is does in Single mode. It's just to tell you the trigger state, Armed/Ready or Triggered. Single will STOP the acquisition. Try Normal too.

author: deezdrama
author_rank: Contributor
timestamp: December 12, 2022, 04:01:40 pm
content: Quote from: tautech on December 12, 2022, 02:09:43 amThank you!I ordered a cheap 1Hz -1MHz signal generator to play around with different waveforms and to play with triggering etc....Once Im comfortable with the scope and move on to testing the chassis board in a monitor im having problems with.... Im wondering how I will probe the legs of surface mounted IC packages with the scopes included hook probe?Are there normal probe tips I can buy, or should I be soldering on jumper leads/wires to my test points on situations like that?

author: tautech
author_rank: Super Contributor
timestamp: December 12, 2022, 06:48:15 pm
content: Quote from: deezdrama on December 12, 2022, 04:01:40 pmThe probe hook/top hat pulls off and then you have a pointed tip for fine work however removing the top hat also exposes the Gnd ring which adds a second hazard to probing live circuitry.They expressly are the risk of shorting 2 points in the PCB for which in the probe accessories pack there are 2 yellow probe condoms to cover part of the tip and all of the Gnd ring of which remove the 2nd hazard namely shorting part of the circuitry to the Gnd ring on the scope.One of the condoms is shaped to perfectly fit over DIP IC leads to prevent slippage and shorts between adjacent pins.Siglent NA have these probe accessory packs should you ever lose them:https://siglentna.com/product/probe-accessory-kit-pak1/

author: deezdrama
author_rank: Contributor
timestamp: December 12, 2022, 09:11:33 pm
content: Quote from: tautech on December 12, 2022, 06:48:15 pmThank you!!!I tried to give the hook end of probe a tug the other day to see if it came off and felt like it wouldnt and didnt want to break it. Ill check it out again when I get home.I wondered what those little yellow caps were for, makes sense now 🤣

author: Martin72
author_rank: Super Contributor
timestamp: December 12, 2022, 11:00:18 pm
content: Quote from: deezdrama on December 10, 2022, 07:56:55 pmThe "idea" or better the warning in most of the service manuals from CRT TVs are based on the fact that the chassis are not grounded to earth.(2 pole mains plug).And there are "hot", will mean the chassis gnd could have high potential, depending on how the mains plug is connected.It´s a 50:50 chance to have neutral or phase on the chassis.The scope´s input gnd is the same as it´s Earth potential.So when the TV chassis it´s gnd have phase potential and you connect the gnd clip of your probe to chassis gnd for measuring....BAMM.A 100:1 probe won´t protect you for this as it´s gnd is also the gnd of the scope/earth.(When measuring with a DMM you don´t have this problem, ,but as mentioned before, with a DMM you won´t "see" everything.*)To avoid this risk, the recommendation came up to use a galvanic transformer for the DUT.(As I´ve started to work in the testfield here, the guys who were already there use the transformer to isolate the SCOPE...)Differential probes are more convenient to use, are not really isolating potentials from each other, got the advantage of switchable input dividers, got the possible disadvantage of noise when looking at lower signals, limited bandwith (for your purposes not remarkable).There a cheap but good ones avaible from micsig.Martin*)https://www.eevblog.com/forum/repair/hioki-3532-50-lcr-schematic-service-manual-wanted/msg4575439/#msg4575439Actual example why a DMM is often not enough..

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2022, 02:05:02 am
content: Quote from: deezdrama on December 12, 2022, 09:11:33 pmThe hats always come off, just pull harder. They have to fit snugly enough that they don't come off from the weight of the probe tugging on it when you've got it clipped onto something.

author: Brumby
author_rank: Unknown
timestamp: December 13, 2022, 11:33:06 am
content: I will always recommend differential probes over an isolation transformer.Why?Using differential probes is very straightforward and uses an unaltered circuit topology, where the risks are easy enough to understand. An isolation transformer changes that topology which can introduce risks that arenot easily identifiableand can cause catastrophic failure and/or potentially lethal situations.

author: bdunham7
author_rank: Super Contributor
timestamp: December 13, 2022, 04:31:28 pm
content: Quote from: Brumby on December 13, 2022, 11:33:06 amUsing an isolation transformer to remove the ground-reference of mains power, disconnecting or breaking the PE circuit, using a differential probe and using an isolated probe or scope are in fact four different things that each need to be considered individually--they are not interchangeable options.

author: Brumby
author_rank: Unknown
timestamp: December 14, 2022, 12:22:06 am
content: The best option will depend on use case - but my comment was directed at the simple either/or choice so often discussed - especially in regard to safety.In short, you arefarless likely to damage equipment or cause injury with differential probes than with an isolation transformer.

author: Martin72
author_rank: Super Contributor
timestamp: December 14, 2022, 11:39:30 pm
content: You shouldn´t use an isolating transformer on devices which got a protective earth connection( 3pole mains connection).This is electronics basic knowledge, if someone don´t know this, he should keep his fingers away from mains powered devices in general.