DT71 Mini-Tweezers: Problems, Repair,Teardown, Firmware-Update,

[@OriolSanchez]

Repaired mine by removing the shorted battery, still though if you require a new battery look for 350829 and 50mAh on Aliexpress, I found some that fit measures close to 30mmx8mmx3mm (should fit)

[@harleystidham2871]

Thank you for helpful video I was able to disassemble the device safely and found both batteries were bad 😮. So I removed them both and drilled a hole in the outer arm cover and ran wires out and soldered on a battery I removed from a rechargeable disposable vape. It works perfect and charges normal. Secured cell with heat shrink/ thermal pipe. You rock thanks again

[@mrpetit2]

This is pretty much why I don't like Lipo cells in test equipment. These are 'non serviceable' but even if they're more easy to get out (like some DMM's that run on a lipo): I buy test equipment to last decades. This one fails within a year. And in 5 or 10 years? are there still cells/parts available in that form factor? When using normal style batteries (AA/AAA or even coin cells like lr44 etc) you're pretty much guaranteed that you can get them still in 10 or 20 years time.

[@Himmelgrau68]

I had this exact same problem. I only used the device one time, and after I pulled it out of the drawer after about a year. Your video helped me to repair it! One of the batteries was damaged. There was a lot of goop under the Kapton tape. Now it is limping along on one battery. I am not looking for a replacement battery. As you mention, it does not seem very easy to find a replacement here in Germany. Would anyone know where I can find a replacement?

[@Himmelgrau68]

Just an update. I was unable to find a replacement battery, so I contacted the manufacturer via the contact form on their website at the following URL: www.miniware.com.cn/contact-us/ Instead of sending new batteries, they offered to send me a replacement tweezers (without the controller) for 20 euros, which I find was very kind of them. They seem to offer great support.

[@roopi67]

Use the command-line DOS prompt to copy the firmware file onto the device. This I also use with other miniware products, it works without fail everytime

[@KainkaLabs]

No, the original firmware was corrupted. Miniware send me a new device and with that firmware update worked as expected.

[@roopi67]

@@KainkaLabs okay thanks for the reply. On a sidenote I'm buying a MS8911 on your advice 👍

[@sjm4306]

I have one of these in a drawer for the rare instance I need to measure inductance/capacitance and your video made me remember it's been awhile since I last charged it. Yep mine has the same issue as yours, will sit on charge forever and never actually charge. Do you have any tips on how to safely open the tweezer part to get to the batteries?

[@KainkaLabs]

just watch the part of the video where I reassemble the part. It´s just the reverse order and I mention it.

[@sjm4306]

@@KainkaLabs I rewatched it (watched it this morning while eating so I may have missed it) just now and I still want to know specifically if there are clips or adhesive holding the outer arms on. I had a few minutes after breakfast before I had to leave for work to try prying it but mine seem very secure almost like the plastic is sonically welded and I was worried prying would damage the plastic/flex or even the batteries. Update: found another teardown video and looks like it's just glued so hopefully a little hot air will help to open mine. It's a shame that this critical flaw mars an otherwise neat implementation. I'll probably just remove the batteries completely and have two wires that extend to plug into usb to power the tweezers from a power bank or external 18650.

[@KainkaLabs]

My motto: "You can´t do more damage to an already broken device". When you have unscrewed all 3 screws of one arm, take also out the little square thing, where the probe tip is slid in the arm. Then you can pull the upper part of the arm (where it was held with the 2 screws) off from the lower part. I think it is held with a clip, but you can´t break it. Even if, the screws are holding the 2 parts together anyway when re-assembling.

[@sjm4306]

@@KainkaLabs thanks, I'll try again this weekend

[@rhirsch81]

My DT71 stopped working in exactly this way. Really disapointing.

[@SianaGearz]

Why shouldn't two cells be connected in parallel, if they're pre-balanced? The only problem i can think of is if one of the cells has an increased self discharge, other cells will be drained as well via compensation currents to equalise their voltages, though those should be very small; and that adding up permissible charge currents can be a little dicey, though setting charge current as high as one cell allows should be OK. As to increased self discharge issues, in a simple series pack you don't usually have continuous balancing either, best case protection control which will equalise the cells when they get fully charged or disables the pack when any one cell is fully discharged, but practically the performance of the pack is also reduced correspondingly. I think the device temporarily falling off the bus automatically to accept changes is rude, as just because a write has occurred, doesn't mean that it's complete! They should have you eject the disk from the operating system and it should restart the device then.

[@KainkaLabs]

You already named a number of problems with cells in parallel in your comment and one of the possible problems is the reason for the failure here :-) Thank God these miniature cells only have about 185 mAh = 666 Joules in nstored Energy. Think about 2 large cells in parallel out of which one develops a short and the other dumps its whole energy into the shorted one. That would give one of those nice videos where first you get a cloud of white smoke and then a fire or explosion. That is why with lithium cells you always need balancing circuitry. Lithium cells are simply too dangerous in case of failure.

[@AdityaMehendale]

They can, and they often are. Whenever you hear a designation e.g. "3s2p" there are 3 in series (~12V thus) and 2 in parallel (so typ. 4Ah) Within the pack there are 6 individual "cells" (3x2 = 6). Imagine what a fireworks display a 5s4p pack can become - 5s2p or 5s4p is typical in large power-tools. There are therefore some protection-mechanisms built-in within the pack. Search for "powerpack teardown" if you are interested. Andreas Spiess did one a few days ago, albeit for a smaller pack.

[@AdityaMehendale]

PS - cylindrical cells are usually more robust than pouch or prismatic cells. Most paralleled configs are with cylindrical cells. With a pouch cell, instead of putting multiple in parallel, you could just use a bigger pouch. Cylindrical cells are usually "one-size" (18650) and hence more "lego-blocks" modular for the designer.

[@KainkaLabs]

But you name it. In these "power-packs" with serialized and paralleled cells most often the cells have each a protection circuit either hidden under the top-contact or by external circuitry. AFAIK only NiMH or NiCd or similar can be paralleled without extra balancing circuitry because they usually don´t catch fire in case of a failure.

[@Bluebuyz]

Thank you so much. your very helpful :)

[@migsvensurfing6310]

I guess the morale is, dont buy this thing. Thanks for the video.