Hantek 6022BL blew up by shorting ground probe - Page 1
Forum section: electronics / repair

author: box25
author_rank: Newbie
timestamp: June 16, 2018, 10:38:25 am
content: Hello,I am in an apprenticeship for an electrical job, and on the office we have Oscilloscopes, which are galvanic seperated form ground.I didn't knew that not all oscilloscopes are galvanic seperatet, so I connected the ground of my Hantek6022BL to an output of an full bridge rectifier and in these moment (positive probe wasn't connectet) the oscilloscope, the messured rectifier, my tower computer and the hole rest of my room went out.After resetting my Fuse, which was an B16 Fuse (16A overload and 3 to 5 times overload current for immediate shutoff) my room had electricity again but my computer and oscilloscope and also the rectifier didn't worked. The computer came back to live after 5 minutes being sad about blowing up my expensive Computer, but the oscilloscope didn't came back to live.The Oscilloscope have an internal short circout, atleast the computer is telling me that there is an large overcurrent on the USB port when plug in the oscilloscope.So basically I have 4 questions:1. does sb. know how to repair the oscilloscope, i read about someone in this forum, who had the same problem, but I can't remember, where i read it. I think th wrote sth. short about that he replaced the part D1, which I think is a kind of speccial diode directly on the Probe connectors, is this the right Part?2. I read about some "Upgrades" which you can make to your hantek scopes th have more samples etc. are these upgrades also available for my Scope (building them in when i have opened my scope for repairing it)?3. Am i overlooking sth., or are these grounded scopes verry dangerous, because you can kind of never know if a Power supply is properly galvanic seperatet? Is it maybe a smart idea to try to never use the ground Probe and only if there is no current shown, then messure your potential messuring Point for the ground clip first by connecting the positive messuring clip to it and look if the scope is showing something and only if it shows always 0v then connect the ground probe to the point and then the positive probe back to the point you want to messure?4. What Protective class does such a scope have? because class it has no real grounding on the metall chassis because if you use an Laptop the chassis of the Laptop and the scope is the potential of your ground Probe which could be mains power and so be deadly, it also is not insolated (metall chassis) and it is not only low voltage because you can stick the ground probe to theoretical evvery voltage level if you don't know what you are doing (kind of what I did...)Thanks for your Support, and yes, now i have seen the video about the dangers of an scope without propper galvanic seperation.

author: janoc
author_rank: Super Contributor
timestamp: June 16, 2018, 12:32:29 pm
content: The scopes are not dangerous. Fools who poke around stuff they don't understand and don't know how to handle it safely are dangerous.Did you "measure" the bridge rectifier at the mains side of an AC supply or some crappy capacitive dropper type "supply" (i.e. not galvanically isolated) by chance? Otherwise I can't see how the bang you describe could have happened. What the heck did you expect to see there? Output of a mains rectifier in Germany is at some 340V, your Hantek has 35V max input voltage. Even a 10x probe wouldn't have protected it from damage (and ignoring the fact that common probes aren't rated for it neither). Be glad you didn't get electrocuted and consider it a lesson that you shouldn't poke around mains if you don't know how to do it safely.Pretty much every single scope on the market is mains earth referenced for safety (i.e. you have mains earth on the chassis and the BNC body). Your USB scope is the same because your PC was ground referenced (also for safety) and the USB lead connected the grounds together. What you have seen at the office is very much an exception and unless those scopes are the portable, battery-powered kind, isolating an oscilloscope from ground is a potentially dangerous practice. Imagine what happens if there is a fault in the power supply or the device under test and you get mains voltage on the scope's chassis - where your BNCs are and the probe that you have in your hand is. If the scope is earthed it trips the breaker. If it is not, you are dead meat ...If you don't want to destroy your equipment (and get potentially killed), I strongly suggest watching this video:That should hopefully also answer some of your other misguided questions.Re your blown up Hantek - you will have to take it apart and see what got destroyed. I would expect that the USB connector or the input BNC and the board around them are likely very charred and burnt because all that short circuit current has gone through there.

author: Ian.M
author_rank: Super Contributor
timestamp: June 16, 2018, 12:50:46 pm
content: Is the PC USB port the scope was on even still working?Often mishaps like that burn traces off the motherboard. If you are lucky the rest of the PC may work but that USB part, and possibly others on the same root hub may be permanently dead.Plug in something like a cheap USB light to that port and see if its still got power, then try a USB thumb drive you don't care about.I'd rate your chances of repairing the Hantek 6022BL as no more than 50% - if you are good at SMD rework and can get the right parts. It depends if the surge took out more than its PSU section. If its taken out the MCU its probably B.E.R. A good place to start would be a teardown. Go over the board with a magnifier looking for tiny burn marks on chips etc. + post a photo here of the board + closeups of any visible damage. If its a charred mess, at least you'l know you are S.O.L. quickly.However the lesson you have (hopefully) learnt is cheap at the $100 or so replacement price - far cheaper than being fitted for a pine box!

author: james_s
author_rank: Super Contributor
timestamp: June 20, 2018, 04:16:19 am
content: A scope with galvanic isolation is very rare, it's pretty much standard that ground on the scope is connected to earth. This is why it's important to know how to properly use your test equipment when working around high voltage.