Replace resistor in UNI-T UT30C - Page 1
Forum section: electronics / repair

author: PedroSpa
author_rank: Newbie
timestamp: June 07, 2023, 07:29:25 pm
content: Hi.My UNI-T UT30C multimeter is malfunctioning so I opened it and there is a burnt resistor. I can only see brown and gold but not the two middle colors. Is there a way to find which resistor it is, or anyone knows which one?I found this article athttps://www.circuitsonline.net/artikelen/view/49/2and it's similar to minehttps://commons.wikimedia.org/wiki/File:UT30C.JPGCan I replace it with that resistor?I attached some photos.

author: Shonky
author_rank: Frequent Contributor
timestamp: June 08, 2023, 01:47:36 am
content: It's obviously not identical but would appear quite close so likely the same or similar value. Looks like 1k from the other unit? You can't see any red (i.e. brown black red gold) on the burnt one?

author: wasedadoc
author_rank: Super Contributor
timestamp: June 08, 2023, 11:44:42 am
content: I have the UT-30B version. The internals are not identical to any of the photos posted above. It does have SMD resistors. It has an R15 with one end connected to the V/OHM jack and one end of the fuse. Bands are brown, black, black, red and blue which is 10k 0.25% and it does indeed measure 9.98k using another cheap meter. So I doubt the burnt one was 1k.

author: PedroSpa
author_rank: Newbie
timestamp: June 08, 2023, 12:06:42 pm
content: Hi. Thank you for replying.No, I can't see the other colors because it is burnt all around. I can't confirm if it's black or brown or any other color, sorry.My meter and the one I mentioned are the same model (the red part is just a cover), have exactly the same functions if you look closer, and the resistor connects the middle "VRmACº" pole to a point on the selection wheel, see attached photos.What's the worst that could happen if I replace it with the resistor from the circuits online one?I know this is a low end device but I have it for more than 15 years and I would not like to throw in the the trash just because of a burnt resistor.Thanks.Edit: just to add that the meter works fine except it does not read correctly.

author: PedroSpa
author_rank: Newbie
timestamp: June 08, 2023, 12:16:29 pm
content: Hi wasedadoc. Thank you for replying.This burnt resistor is the R16 see attached photo.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 08, 2023, 12:23:45 pm
content: My R15 appears to be in the same electrical position as your burnt one. I would try a 10k resistor and check if the readings are correct. Only if they are far from correct would I change to 1k. i'll post a photo soon.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 08, 2023, 12:44:36 pm
content: UT-30B. Differences from UT-30C are that B has no temperature range. Range dial has the current ranges rotated anticlockwise so that 10A on B in in temperature position of C. Position of 2000uA range on C is used for extra 200uA range on B.Photo shows R15 on PCB of UT-30B purchased in 2012.

author: Shonky
author_rank: Frequent Contributor
timestamp: June 08, 2023, 11:03:15 pm
content: Yeah very hard to see that as multiplier as red even from the most recent photo.I would go with 10k based on wasedadoc's info and see what happens.