Digital Clamp Multimeter display nothing - Page 1
Forum section: electronics / repair

author: zillah
author_rank: Contributor
timestamp: October 10, 2025, 11:19:40 am
content: Dear ExpertsI have got Proskit MT-3109 AC/DC Digital Clamp Multimeter, very rarely used , I needed to use it recently I realized nothing display in the screen I replaced the 3xAAA batteriesBut still nothing display in the screenhttps://pacific-electronics.com/pro-skit-mt-3109-ac-dc-digital-clamp-multimeteri was trying to see if any fuse blown up I removed the back cover but I couldn't see any fuseThx

author: Kean
author_rank: Unknown
timestamp: October 10, 2025, 12:06:14 pm
content: The battery terminal on the PCB near D2 (on the right) looks corroded.Did the batteries leak?How does the battery compartment/springs look?

author: zillah
author_rank: Contributor
timestamp: October 10, 2025, 12:12:54 pm
content: When I replaced the batteries I didn't notice any leakPlease see the attached photos for batteries compartment

author: Kean
author_rank: Unknown
timestamp: October 10, 2025, 12:36:39 pm
content: Well that battery compartment doesn't look too bad.The battery contact on the PCB definitely looks crusty and needs cleaning.What about the spring on the back of the battery compartment that contacts that pad?Handheld DMMs generally don't have a fuse for the battery power, and a clamp meter wouldn't normally have a fuse as you don't measure current with the test leads.

author: zillah
author_rank: Contributor
timestamp: October 10, 2025, 12:48:29 pm
content: Thx KeanI will try to clean that , any suggestion what solvent do I need to use with brush ? or just brush no solvent ?I have attached photos showing contacts of the compartment with PCBRegards

author: BILLPOD
author_rank: Frequent Contributor
timestamp: October 10, 2025, 01:36:04 pm
content: Good Morning Zillah, You say 'new' batteries were installed. My experience has shown me that batteries, fresh out of the box are not always good, so I always load test 'new' batteries before I install them. Also, take another look at your battery orientation; it's happened to me more than once that I installed one battery backwards, in a multi-cell application, (it happens to all of us eventually).Using your DMM, check the voltage of each cell 'individually, and then measure the total at the end of the set to ensure you have +- 4.5 VDC.

author: zillah
author_rank: Contributor
timestamp: October 10, 2025, 11:39:33 pm
content: Thank you very much BILLPOD for your helpI did replace 2 set of batteries and I did test the voltage for each battery by using Fluke 177 MultimeterAnd I did check batteries orientations as well but still no joyRegards

author: marhuum
author_rank: Contributor
timestamp: October 11, 2025, 12:04:38 am
content: simple;any mild/weak acidCitric avid, acetic acid, or phosphoric acid, etc

author: zillah
author_rank: Contributor
timestamp: October 11, 2025, 12:29:50 am
content: Thx marhuumNoted

author: Jan Steinman
author_rank: Contributor
timestamp: October 13, 2025, 09:06:45 pm
content: Quote from: zillah on October 10, 2025, 12:48:29 pmFor battery terminals, I use an ink eraser (for light corrosion) or a nail file (for heavy corrosion).Generally, you can't take battery corrosion off with just a solvent. You need something abrasive.

author: zillah
author_rank: Contributor
timestamp: October 13, 2025, 09:11:05 pm
content: NotedThx for that

author: Kean
author_rank: Unknown
timestamp: October 14, 2025, 01:16:04 pm
content: For cleaning corrosion I typically use a fiberglass pen, or an old style ink eraser as Jan suggested. You can still find the combo ink/pencil erasers for sale.I suspect you will need to solder some wires to inject battery power (e.g. to end of D2 and a similar point for the other terminal). This will allow easy access for probing to trace power and other signals. No idea if there is a schematic available, or if the DMM IC is known.

author: zillah
author_rank: Contributor
timestamp: October 14, 2025, 10:46:39 pm
content: Thx Kean I used to have a fiberglass pen but I don't where is hiding now ,,,I am planning to get one any good one you are happy with it ?QuoteI haven't used this but I am planning to get this :https://stuckonstationery.com.au/product/eraser-ink-and-pencil-faber-castell/

author: Jan Steinman
author_rank: Contributor
timestamp: October 15, 2025, 05:49:34 am
content: You might want to make a simple current probe to tell if the device is drawing power or not.I found some thin, double-sided printed circuit board material, cut it so it could fit between a battery and the contact in a battery holder, and soldered two wires on either side of the PCB, running that to a couple banana plugs, which could be plugged into the current measuring jacks on a DMM.I wanted to include a photo, but Murphy's rule of finding probes got me. ("The special probe you need that you know you have one of can never be found when you need it.")

author: Kean
author_rank: Unknown
timestamp: October 16, 2025, 01:38:11 am
content: Quote from: zillah on October 14, 2025, 10:46:39 pmThe fiberglass pens are nothing special. Mine probably came from RS or Element14 but likely unbranded.That eraser looks fine. I bought a bulk lot of Staedtler Duoplast years ago and I am still going through them.

author: zillah
author_rank: Contributor
timestamp: October 16, 2025, 09:57:25 am
content: Thx Kean