Uni-T UT61E europeans version dead by a rechargable battery - Page 1
Forum section: electronics / beginners

author: Rizaru
author_rank: Newbie
timestamp: January 15, 2022, 06:28:20 pm
content: Hellomy uni-t 61e just dead after I wanted to swap the de battery. I thought il buy those rechargeable ones from energizer at 8.7v.didn't boot up oke I had a normal alkane one as well. but it is completely dead nowCan someone explain how a rechargeable battery can kill a DDM? i have the schematic and only U3 is getting voltage also the Xtal is getting voltage.now i'm whit a dead DDM that doesn't even beep when turned on. I can't wrap my head around it how it can be.ty for you aswers!

author: PKTKS
author_rank: Super Contributor
timestamp: January 15, 2022, 06:50:30 pm
content: I had a similar issue with the same profile...When changing bat the meter refused to turn on....I did a careful inspection and found the culpritbeing a damaged MLCC capacitor just the one thatsits directly connected to the bat.Replaced that with a tantalum and it turned on just fine.That MLCC may get damaged by a dozen different reasons...Schema attachedPaul

author: Rizaru
author_rank: Newbie
timestamp: January 15, 2022, 07:30:38 pm
content: weird thing is there is voltage present on U3 and the Xtal but nothing turns on so I'm guessing the main chip :/ that is shot.

author: PKTKS
author_rank: Super Contributor
timestamp: January 15, 2022, 08:19:51 pm
content: Quote from: Rizaru on January 15, 2022, 07:30:38 pmI had the same bad feeling when that happened...Started to quote the chip... OK we can find the chip..BUT... A single piece isalmostthe price of a new whole unit..That is the dark side of VLSI or COB DMMs...If the chip is damaged you save a few bucks ordering a new one..but last time I checked it was not worthyTry harder to spot a damaged cap or bad cold solder joint...Otherwise ... the alternatives are fewPaul

author: Rizaru
author_rank: Newbie
timestamp: January 15, 2022, 08:33:45 pm
content: Well i think i might have found it. But i don't C36 no where on schematic or i'm looking right over it.Marijn

author: radiolistener
author_rank: Super Contributor
timestamp: January 15, 2022, 09:12:26 pm
content: Quote from: Rizaru on January 15, 2022, 06:28:20 pmif you're using battery with DC/DC converter inside, it can fail and apply high Voltage to the battery terminals, so DMM will be damaged.For example, if your battery has USB connector for charging, it has DC/DC inside.

author: Rizaru
author_rank: Newbie
timestamp: January 15, 2022, 09:46:50 pm
content: it one of thosehttps://www.amazon.de/-/en/Energizer-rechargeable-batteries-Recharge-Power/dp/B000IWXVU6/ref=sr_1_1?crid=1BI1HDA3ZP87G&keywords=9v%2Bbatterie%2Benergizer%2Baufladen&qid=1642283084&sprefix=9v%2Bbatterie%2Benergizer%2Bre%2Caps%2C84&sr=8-1&th=1But it charge whit the pins and a separted charger.O well gonna see what the replacing does of c36. i hope it turn on again.

author: Per Hansson
author_rank: Unknown
timestamp: January 16, 2022, 03:18:33 pm
content: Quote from: Rizaru on January 15, 2022, 08:33:45 pmIt is located in the lower middle of the schematic, see attached crop where I've marked C36.

author: PKTKS
author_rank: Super Contributor
timestamp: January 17, 2022, 03:49:50 pm
content: Just looking by the photo it seems really toasted...Looks identical to the other below.. tantalum? or MLCC...In fact you can even fit a small THT tantalum cap there...They are bigger more robust ...Just a bit of skill to put them there..Paul

author: theHWcave
author_rank: Regular Contributor
timestamp: January 17, 2022, 11:32:29 pm
content: My 5 cents: There does not seem to be any diode protecting the meter from putting the battery the wrong way around. I know you can't clip it in with the polarity reversed but its enough to just hold the battery the wrong way around against the terminals temporarily, - realising "oh its the other way around" and then turning the battery and plugging it in. But the damage is already done. I'v nearly done this a couple of times myself. 9V batteries and their exposed terminals are dangerous, especially if is its a beefy battery (for 9V that is) that can deliver a high current.The schematic shows a VB+ that may go somewhere without being switched. If so I have not found where but that would be a prime candidate for damage. VC+ seems to be VB+ after being switched. If this is true then damage (blown up caps) by a temporarily reversed battery should only be possible if the meter was left on while the battery was changed.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: January 19, 2022, 08:40:31 am
content: those 9V blocks based on Li-batteries and internal DC/DC maybe look tempting, but they are a PITA; not only the cause voltage spikes, they do generate considerable noise, what can be heard when using them in audio appliances. I struggled over that when using such a beast in my acoustic guitar. After that, I threw all of them out.NiMH are maybe not the best solution, but as long as there are no Li 9V-blocks with clear and reliable specs, it's better to leave the fingers from them. So far I only know them from Ali & co, so you can search for a long time to find out what you get.