Which isolated o'scope for mains SMPS repair?

[crystallattice]

Thanks BravoV,

A crappy scope with a fancy gadget attached is , well , just that!

I'll have a look at the gadget you mentioned and then also look for a cheap digital scope/portable scope. What did you end up going for The THS720?

PS. the TPS2024B is still available, but only has generic probes. He is planning on getting some standard Tektronix probes but I told him rather not let me get the high voltage ones. Still negotiating.....

Would standard 10:1 100:1 probes not also "work" if you are willing to "live on the edge"?

[BravoV]

A crappy scope with a fancy gadget attached is , well , just that!

I'll have a look at the gadget you mentioned and then also look for a cheap digital scope/portable scope.

LOL, yeah, but beware though, these ancient Tek probe isolator is gigantic  , here the one I scored last year, I just let the photo speaks for it self, comparing to common current cheap DSO size. Its like the probe is swallowing it's own scope. 



Luckily it works as expected, love it very much. 

What did you end up going for The THS720?

4 years ago I scored a THS710A with complete accessories, actually I made a questioning thread for it during the bargaining period -> HERE.

PS. the TPS2024B is still available, but only has generic probes. He is planning on getting some standard Tektronix probes but I told him rather not let me get the high voltage ones. Still negotiating.....

Would standard 10:1 100:1 probes not also "work" if you are willing to "live on the edge"?

Suggesting to be careful for such expensive "used" stuff, isn't this way over your budget ? My worry is as its used, the risk of its not working properly or out of cal. If that is local offer, if possible, do a physical verification. For me personally, able to do a physical verification worth 10 to 20% of the price rather than buying it online relying just on the photo and the seller's claim.

Regarding isolated probe, well, if you're willing to bet on it, here, Aliexpress's grade probe  , these are just examples, there are many same offer there. Its all fully isolated with no exposed metal at all.

Price wise, these probe is relatively cheap imo, say compared to 1st tier branded ones.

P2301C Probe 100:1 High Voltage Withstand 5KV 300MHz
https://www.aliexpress.com/item/1PCS-wholesale-P2300C-Oscilloscope-Probe-100-1-High-Voltage-Withstand-5KV-300MHz-for-oscilloscope-Tektronix-HP/32352684108.html

P2301B Probe 10:1 BNC protective cap DC-300MHz
https://www.aliexpress.com/item/Authentic-1PCS-P2300B-Oscilloscope-Probe-BNC-protective-cap-DC-300MHz-Scope-Clip-Probe-300MHz-For-Tektronix/32352680753.html

Hope this helps.

[crystallattice]

Wow, that probe makes your scope look like the accessory!

Spoke to the TPS scope guy and he is also collecting test equipment for his hobby but sounds like he settled on Fluke 190 so selling the Tektronix, he has offered to bring it along next month when he is in my area so I can test it. Not sure if it will still be available though....

Thanks for the probe links. I have bought a set of test leads from the same "brand" and they seem quite decent, at least for what you pay. Unfortunately I  had a bad run in with Aliexpress a while back so staying clear from them. Ebay buyer protection is at least fair!

[capt bullshot]

PS. the TPS2024B is still available, but only has generic probes. He is planning on getting some standard Tektronix probes but I told him rather not let me get the high voltage ones. Still negotiating.....

Would standard 10:1 100:1 probes not also "work" if you are willing to "live on the edge"?

As far as I know, the TPS2024 has standard probes (10:1) when delivered. The high voltage isolated ones have to be bought extra (e.g. the P5120 20:1 ones). Any probe that you can compensate will work with the TPS2024 (as with any other oscilloscope). The user interface (and all the other features) of the TPS2024 is quite similar to the TDS2024 (non-isolated) series, so you'll get a "normal" DSO with the additional isolation feature.

[David Hess]

The Fluke 190 series has input channels that are fully isolated from each other. Also, the scope is rated CAT III 1000V and CAT IV 600V. If you're working on live circuits and your life is worth anything to you, that's what I would use. They're a bit pricy though.

The older Fluke Scopemeters can be had for reasonable prices.  Usually the only problem with them will be worn out batteries.

The LCD displays they have are not very good but are usable and they support peak detection making them a reasonable DSO if you cannot have something with a better display.

One of their advantages is that they also make pretty good multimeters.

[shakalnokturn]

On the paper the Chauvin-Arnoux/Metrix Scopix III or Scopix IV look really overkill handheld scopes: Up to 4x 300MHz, 2.5GS/s, 12bit ADC.
No clue how good the user interface is though, that is a detail that can ruin decent hardware.

http://www.chauvin-arnoux.co.uk/sites/default/files/D00SAK91_16.PDF
http://www.chauvin-arnoux.co.uk/sites/default/files/HLHBDYSZ_0.PDF

[crystallattice]

hi,

The Chauvin-Arnoux/Metrix Scopix does look pretty impressive but I think the price tag will put me off a bit, secondhand they are already expensive! Also, it seems they are sold under different names...

The chap with the TPS2024b has agreed to $1000 without fancy probes (just 4 generics). The question now is how to properly test the scope? The warranty sticker at the back has been broken so not sure if it was opened/repaired/calibrated or just accidentally broken?

Scope comes from a cell repair  shop that went bust and an employee bought it on the auction, or so the story goes.

So are there any quick tests that one can perform with limited tools to verify the integrity of the scope? I'm not talking about calibration accuracy, but just make sure everything is functioning as it should?

[capt bullshot]

You can check basic functionality by measuring the "Probe Comp" signal with each channel, using the supplied probes. This should display a nice rectanglar waveform, if the probes are properly compensated. Just connect one probe to channel 1, and probe this signal, adjust the scope for a stable waveform, if the waveform does not have clean edges, try to adjust the probe compensation. Then move the probe to CH 2 and repeat. You should also check all probes this way.

Then search the "error log" and "self test" (or "self cal")  within the menus, and check those.

[crystallattice]

Will check error log, didn't know it existed.

How "accurate" or reliable is the self test? Is this what the factory uses on the assembly line before they ship it....

[Fungus]

How "accurate" or reliable is the self test?

Oscilloscopes aren't multimeters. Their main use is to see wiggly lines on screen, you can only expect accuracy of a few percent in readings.

Is this what the factory uses on the assembly line before they ship it....

Yes.

[Fungus]

You can check basic functionality by measuring the "Probe Comp" signal with each channel, using the supplied probes. This should display a nice rectanglar waveform, if the probes are properly compensated. Just connect one probe to channel 1, and probe this signal, adjust the scope for a stable waveform, if the waveform does not have clean edges, try to adjust the probe compensation. Then move the probe to CH 2 and repeat. You should also check all probes this way.

Sorry, no. Each probe should be calibrated for a particular channel. You should only connect a probe to the channel it was compensated for. Most probes come with little colored rings to put on the plug so you know where they're supposed to go.

[forrestc]

Since this thread is still alive:

Is this the best option or are there other options like a cheap handheld scope + some isolated differential probes added on for isolation?

I've recently become a big fan of differential probes, and specifically the EEVBlog HVP-70's that Dave sells.  But I'm using these on a bench with a fixed oscilloscope, not sure if you really are looking for something portable - dealing with the separate probe box and batteries or power supplies would be a pain in a mobile situation.

-forrest