Chip identification, Voltcraft vc 890 - Page 1
Forum section: electronics / repair

author: EinRainerZufall
author_rank: Newbie
timestamp: January 11, 2020, 10:31:09 pm
content: Hello, I bought a cheap defective Voltcraft vc890, but unfortunately cannot find out the names of the defective components. If someone can help me who has this DMM or takes good pictures, I'm very grateful to them.Q1 and Q6 are the broken ones.

author: fzabkar
author_rank: Super Contributor
timestamp: January 11, 2020, 10:59:05 pm
content: Q1 looks more like an LDO linear regulator than a BJT or MOSFET, otherwise I can't understand the purpose of C28.

author: EinRainerZufall
author_rank: Newbie
timestamp: January 12, 2020, 02:15:57 pm
content: i found out that Q6 is labeled with A4 and is a BAV70W or something similar is. And Q1 i cant read well but on it stant A183A or A1B3A but unfortunately i can't find none of this.

author: fzabkar
author_rank: Super Contributor
timestamp: January 12, 2020, 08:16:14 pm
content: The ES51997 IC requires a 3V supply. You might like to trace its supply pin back to Q1 to test whether Q1 is a 3V regulator.

author: EinRainerZufall
author_rank: Newbie
timestamp: January 12, 2020, 10:18:53 pm
content: Good idea and yes after i traced it out it is the 3v regulator. The next is with how much output current i should calculate ? The package is SOT89

author: fzabkar
author_rank: Super Contributor
timestamp: January 13, 2020, 01:49:41 am
content: Page 5 of the datasheet specifies 3.2mA as the maximum operating current in DCV mode.http://www.cyrustek.com.tw/spec/ES51997.pdfHave you determined the pinout?

author: wraper
author_rank: Unknown
timestamp: January 13, 2020, 02:04:48 am
content: Quote from: fzabkar on January 11, 2020, 10:59:05 pmDisconnecting power.

author: ebclr
author_rank: Super Contributor
timestamp: January 13, 2020, 08:01:19 am
content: A4 Mark is BAV70

author: EinRainerZufall
author_rank: Newbie
timestamp: January 15, 2020, 12:28:53 am
content: Sorry for the late post, I had a lot to do. I found out the pinout.

author: fzabkar
author_rank: Super Contributor
timestamp: January 17, 2020, 12:51:37 am
content: I'm wondering, would it be safe to test the unit with a 3V lithium coin cell?

author: EinRainerZufall
author_rank: Newbie
timestamp: January 18, 2020, 03:10:21 pm
content: At the moment i haven't a 3V lithium coin cell but i powered the meter with my lab supply and on 3.3V it goes on and draw around 50 mA. Do you think i can replaece it with this from Mouser ?https://www.mouser.de/ProductDetail/ABLIC/S-812C33AUA-C2NT2G?qs=%2Fha2pyFaduhHm29h3nOKRaOvQ7dXk97IvZXrSBdi%2F6D2yC%252BLFVwsLA%3D%3D

author: fzabkar
author_rank: Super Contributor
timestamp: January 18, 2020, 09:04:16 pm
content: It's a 3.3V regulator rather than 3.0V. I don't know whether that's OK, or whether it affects the calibration.

author: EinRainerZufall
author_rank: Newbie
timestamp: January 19, 2020, 12:49:45 pm
content: Quote from: fzabkar on January 18, 2020, 09:04:16 pmWhat do you mean ? The part that i linked is a 3.3v regulator.

author: MilanM
author_rank: Contributor
timestamp: February 04, 2020, 10:34:51 pm
content: HelloI had similar situation.Here is my topichttps://eevblog.com/forum/repair/voltcraft-vc890-big-current-consumption-180ma/Well regulator is used to supply g230f128 and its 3.3V regulator.If its dead it probably damaged controller as it was in my case, after replacement current consumption was like 180mA and it drain battery in like one hour which made multimeter useless.

author: EinRainerZufall
author_rank: Newbie
timestamp: February 04, 2020, 11:17:33 pm
content: Quote from: MilanM on February 04, 2020, 10:34:51 pmI replaced the 3.3V regulator and jet the multimeter work perfekt and the current consumption is 40mA.

author: MilanM
author_rank: Contributor
timestamp: February 04, 2020, 11:29:54 pm
content: Yes 40mA is normal current consumption! Congrats you got it working!