Klein MM problem - Page 1
Forum section: electronics / repair

author: joshcarr
author_rank: Contributor
timestamp: September 22, 2017, 06:41:40 pm
content: I've got a Klein multimeter basically the same as the MM400 model. I haven't used it in awhile and it turns on fine but reads zero for everything. I bridged the fuses which changed nothing and replaced the battery. Any Idea what the issue could be? Thanks.

author: kalel
author_rank: Frequent Contributor
timestamp: September 22, 2017, 06:48:11 pm
content: Quote from: joshcarr on September 22, 2017, 06:41:40 pmAre the probes making good contact? I don't know if this ever happens on quality meters, but I have had probe/terminal contact issues before.Does the continuity beeper work? If something was shorted on the input, it might beep without the probes being in contact.Unrelated to your issue but related to the similar meter, on this link (searching for MM400 got me there):http://www.kleintools.com/catalog/multimeters/digital-multimeter-auto-ranging-600vI can't read what is displayed on the meter:Camera/photo issue or meter issue?

author: joshcarr
author_rank: Contributor
timestamp: September 22, 2017, 07:06:50 pm
content: It only beeps when the probes are touching but they have to be touching in a specific spot. Which I would thing means that the leads are bad but if I connect the contacts themselves that the leads attach to it also has to be very specific.

author: Twoflower
author_rank: Frequent Contributor
timestamp: September 22, 2017, 07:18:30 pm
content: The meter just changed between 4 and 5 for the V and between 2 and 3 for the 0.1V place during the exposure of the cam. You could tell that because the segments that are identical for both numbers are easy to see while the others are only dim.Wrt. problems with the meter. Do you have other leads or two pieces of wire for a test. If you use wires for this test: DON'T use that for anything that could a) have dangerously high voltage (e.g. stay below for this test 10V) and b) provide a very high current (e.g. don't use a starter battery). For this test a AA battery will work well.Your description sounds like a oxide layer on the tips. If that's true you should think about getting better test leads as you can't be sure if there is no voltage or the leads are oxidized. That could be dangerous if you work on potential lethal voltages.

author: joshcarr
author_rank: Contributor
timestamp: September 22, 2017, 07:19:53 pm
content: Even using wires attached straight to the contacts inside the meter it barely beeps so I don't think it's the leads.

author: Twoflower
author_rank: Frequent Contributor
timestamp: September 22, 2017, 07:25:57 pm
content: OK, that sounds like bad contacts in the inside of the meter. You might check first the connection of the sockets to the PCB. For example you could carefully use the diode test to see if the connection is stable if you bridge the correct solder joints on the PCB.A decent picture of the inside might help here to provide advice.

author: joshcarr
author_rank: Contributor
timestamp: September 22, 2017, 08:01:12 pm
content: Here's a picture.https://ibb.co/mAJ69QHow exactly would I use the diode test? The connections look fine to me I'm not really sure how they're supposed to look though.

author: Twoflower
author_rank: Frequent Contributor
timestamp: September 22, 2017, 08:11:53 pm
content: OK. Try to bridge the left fuse (this one is used to protect the voltage jack) and the solder pad right above the D2 label (above the centre jack).Also check the crystal close to the top (right above the black blob). Are the leads touching each other? Carefully to not damage the device.

author: joshcarr
author_rank: Contributor
timestamp: September 26, 2017, 02:59:49 pm
content: I've bridged both fuses at the same time just to eliminate that as a possibility. It seems they are in fact blown though, tested with a different MM. Tried bridging that pad it did nothing. The crystal is fine as far as I can tell no wires are touching. Since both fuses are blown I feel like something on the board got fried. Probably just going to get a new one

author: mrf245
author_rank: Regular Contributor
timestamp: September 26, 2017, 03:09:03 pm
content: Do you have photo show inside your multi-meter? Any other thing burned?

author: retiredcaps
author_rank: Super Contributor
timestamp: September 26, 2017, 07:51:25 pm
content: Quote from: joshcarr on September 22, 2017, 06:41:40 pmYou do realize that the two fuses inside your meter ONLY affect the proper operation of the current readings. With blown fuses, the current readings will always be zero. Volts and ohms are not affected by the blown fuses.When you say zero for everything, do you mean volts and ohms too?Q1. What do you get when you measure a fresh AA cell? Something like 1.5 or 1.6VDC or 0?Q2. What does the lcd display show when you turn the switch to resistance? Does it show 0L or 0? that is, open circuit or zero ohms?

author: joshcarr
author_rank: Contributor
timestamp: September 27, 2017, 01:52:57 am
content: mrf245 there's a picture further up the thread. Nothing looks burned to me. retired caps yes I understand that, which is why I've been doing everything with the fuses bridged, effectively bypassing them and eliminating them as a potential source of the issue. It reads zero for everything. Every setting is a solid zero no matter what I connect or change. Including resistance. I think something driving the LCD screen got fried or stuck in a loop or something.

author: mrf245
author_rank: Regular Contributor
timestamp: September 27, 2017, 03:07:42 am
content: OK I see photo. At Resistance shows zero is strange. Normally is 1.when power on, use your finger to press or touch components surround main IC, is reading zero changing?Maybe main IC dead or crystal issue.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 27, 2017, 05:44:05 am
content: A 0 ohm resistance reading does not bode well. It should read open circuit. My guess is that the main IC is dead. Time to get another.

author: joshcarr
author_rank: Contributor
timestamp: September 27, 2017, 10:30:02 pm
content: Yeah that's what I figured. New one is on the way. Thanks guys.