Voltcarft VC 870 repair - Page 1
Forum section: electronics / repair

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 06:30:46 pm
content: So my story begins when i found this multimeter for 20 euros . I know it was broken but it was worth the risk . I bought it and now i have a little problem so that brought me here.I found what's problem with it and it is just a little SMD capacitor.I can't find any schematics or photos of it. so here i am . If someone know or have same multimeter like me , can you provide me with some data ?Sorry for bad english and thanks in advice !

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 06:42:28 pm
content: Photos:

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 06:46:35 pm
content: +1

author: retiredcaps
author_rank: Super Contributor
timestamp: January 17, 2019, 06:58:48 pm
content: Q8 and Q11 look like they suffered damage as well? Or is it reflections in the photo?Voltcraft usually gets Uni-T to make their meters. See if Uni-T has a 40000 count meter that is equivalent and look for Uni-T schematics.If not, check out the main IC chipset and search for its datasheet.

author: Armadillo
author_rank: Super Contributor
timestamp: January 17, 2019, 08:48:22 pm
content: Attached their nominal connection parts;

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 09:34:05 pm
content: I just wanted to thank you guys allot. I did not expect that fast answer. I will first replace burnt components and then those that are looking "good" . I hope all of you have a great day !

author: Armadillo
author_rank: Super Contributor
timestamp: January 17, 2019, 10:22:49 pm
content: Yoo!, you should wait awhile for other members to make correction or object freely. Nominally that's how they connect up, so best wait a while for someone to open up the exact Voltcraft VC870 for you.

author: retiredcaps
author_rank: Super Contributor
timestamp: January 17, 2019, 10:26:43 pm
content: You should also take apart the front of the meter and check under the range switch for carbon tracks likehttp://mrmodemhead.com/blog/ideal-carbon-footprint/especially since I can see some browning on the pcb.

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 10:36:00 pm
content: I took front part too trying to find something to replace but front was good and clean ! (ps: That browning is from blown capacitor)I will wait for other members to give their opinions . In this time i have one more problem .. no one is selling these transistors here ! Do other company's make same transistors with same specifications?sorry for those stupid questions but i am still learning these thingsi hope you understand

author: Armadillo
author_rank: Super Contributor
timestamp: January 17, 2019, 10:47:38 pm
content: I check the price of this meter, amazon around $190, so it may be worth it to experiment, IMO.I entered the parts in ebay, no problem finding the parts there from china. Have you tried ebay?

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 11:15:48 pm
content: I looked it up on ebay Unfortunately we don't have or use ebay here in Serbia . I can use German one but i ill have to wait like 2 or 3 mounts until package arrives or price for shipping will be rocket high. Still i hope there's alternative .I have found those from aliexpess , alibaba are they any good?

author: Armadillo
author_rank: Super Contributor
timestamp: January 17, 2019, 11:18:10 pm
content: YOu mean you can't go to the US site;https://www.ebay.com/

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 17, 2019, 11:32:43 pm
content: I can go to US one but it is just a same deal

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 18, 2019, 08:03:06 pm
content: YO guys i have a news ! i have found one photo that prove that capacitor! here is the link :https://www.all-electronics.de/digitalmultimeter-vc870/so

author: Armadillo
author_rank: Super Contributor
timestamp: January 18, 2019, 09:47:02 pm
content: What's UP? What's "that capacitor"?

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 19, 2019, 02:24:42 pm
content: this one

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 20, 2019, 02:03:39 pm
content: So I have 1 more question about that 106c capacitor . I can't find out witch one is it 10 V or 16 V ( both of them are named 106C)

author: Armadillo
author_rank: Super Contributor
timestamp: January 20, 2019, 03:22:12 pm
content: If I remember correctly, To load Tantalum capacitor 50% only. [DO NOTE ALL THE POLARITY DIRECTION]. Tantalum very fussy capacitor to reverse voltage.5.5V and 3.3V, what is the point? Simply buy all the same e.g. higher the better.From the different pictures, there are the black smaller ones used and there are the yellow, slightly bigger ones used.Your choice. But instead of concentrating on this, I think you should troubleshoot further why these blew off and whether it's economical to pursue further.Quote from: KermitTheFrogg on January 20, 2019, 02:03:39 pm

author: Armadillo
author_rank: Super Contributor
timestamp: January 20, 2019, 03:44:20 pm
content: Oh, BTW "C" is 16V type

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 21, 2019, 12:28:57 am
content: Check if the battery has any reverse polarity protection diode, if not check if the fried tantalum is straight across the battery.It could be that simple...

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 21, 2019, 02:06:05 pm
content: Great idea! I will check it right away!

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 21, 2019, 02:11:13 pm
content: I just checked it . It has 2 Zener diodes in series so battery polarity wasn't problem . i will keep on searching !

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 21, 2019, 02:13:42 pm
content: Photo:

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 26, 2019, 01:24:25 pm
content: Heeeey guys and girls here is an update !Yesterday i replaced 106C capacitor with new one, nothing special . But today i was checking all components with voltmeter and when i got to the nju7201u35 suddenly backlight turned on. I am still waiting for nju7201u55 , nju7201u35 and mmbt3906 to arrive and then ill update you guys!Note this is old photo

author: Armadillo
author_rank: Super Contributor
timestamp: January 26, 2019, 01:33:26 pm
content: We have one HappY Kermit..... hehehehehehe;happy even with backlight....

author: KermitTheFrogg
author_rank: Contributor
timestamp: January 27, 2019, 02:49:57 pm
content: Yoooo guys now i am a little bit confused about Nju7201u55. I found like NJU7201U55-TE1 and NJU7201U55-TE2 are they just newer version of it or is it totally different thing?

author: KermitTheFrogg
author_rank: Contributor
timestamp: March 23, 2019, 10:44:32 pm
content: New parts have arrived (mmbt3906 & Nju7201u35) and i replaced them and i actually think i did OK job with soldering. I tried to power it on but no signs of lifeI will replaceNju7201u55 and 100nF capacitor but i need to know if it is 100V or 50 V version? But i still think they aren't a problem. I will send additional photos so you guys can help me identify other problems if it has any.Link for photos :https://imgur.com/gallery/Z3nzoLB