extech 430 - Page 1
Forum section: electronics / general

author: adam_lumpkins
author_rank: Contributor
timestamp: July 09, 2011, 03:43:13 am
content: I just got an extech430 true rms, the capacitance function seems to be not working correctly, when in the capacitance mode and the probes on the bench, I get a reading of .18 nano farads. When i try to check a cap "NEW AND OLD" nothing..... now it did read one time on an ceramic cap. but if you leave the probes on a cap. it will read "LO" I need help !!!!!!

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 09, 2011, 06:40:47 am
content: Is this a new DMM or used ?

author: vtl
author_rank: Regular Contributor
timestamp: July 09, 2011, 06:59:55 am
content: Are you trying to measure a capacitor thats out of the cap range? According to the specs the maximum is only 100uF.Source:http://www.extech.com/instruments/resources/datasheets/EX400series.pdf

author: patb
author_rank: Regular Contributor
timestamp: July 09, 2011, 01:49:17 pm
content: I have exactly the same model. Its capacitor measurement feature iscomplete crap. It is very slow, unstable (measurement tends to rise slowly) and if you try to measure anything close to 100uF it will fail (it won't even bother to show 0L sometimes). I thought that my unit is just broken, but it seems that this is "normal".

author: adam_lumpkins
author_rank: Contributor
timestamp: July 09, 2011, 02:00:54 pm
content: It is brand new out of the box

author: adam_lumpkins
author_rank: Contributor
timestamp: July 09, 2011, 02:05:06 pm
content: VTL, I feel so stupid I think you nailed it I didn't look at the specs..... and yes that dose suck ass!!! I was looking forword to having that feature that had a large range

author: Unknown
author_rank: Unknown
timestamp: July 09, 2011, 02:27:44 pm
content: Quote from: adam_lumpkins on July 09, 2011, 03:43:13 amThis is probably the capacitance of the test leads, the value will probably decrease as the distance between the leads increases.I don't understand the obsession with measuring large value caps. Electrolytics are usually well marked, tolerance is rarely critical (stability sucks anyway), and rarely a useful measure of quality/condition. ESR is much more useful for the latter. About the only application I can think of is checking if you got counterfeit components from that dodgy distributor.Small caps are sometimes unmarked (SMD), may have to be matched to high accuracy (eg. in filters), and you may want to measure parasitic capacitance of wires.

author: adam_lumpkins
author_rank: Contributor
timestamp: July 09, 2011, 07:43:14 pm
content: So E.S.R is the way to go for high value caps.? It just pisses me off that the damn thing has the function and don't work!!! I tryed it on low value caps. because of the reply I got about the max range being 100uf and still nothing... The reason I want this is because i was trying to find a all in one meter. I do alot of repair work "vintage TVs" mostly..

author: Unknown
author_rank: Unknown
timestamp: July 09, 2011, 09:04:26 pm
content: Not so much for high value caps, but for electrolytics (and 99% of the >100uF caps are electrolytics). Equivalent series resistance tends to increase with age, and increased ESR makes them less effective as filtering caps. The ideal cap has zero ESR. In applications with large pulse currents (eg. switching power supplies), increased ESR means more heat, which speeds up the aging. Switchers tend to use low-ESR caps for that reason.None of the brand name DMM's incorporate ESR as far as I know. Some LCR meters do, and there are a few dedicated LCR meters (like the Bob Parker design).Maybe other people measure the capacitance of large caps all the time, but I don't see the point.

author: adam_lumpkins
author_rank: Contributor
timestamp: July 10, 2011, 12:23:31 am
content: thank you for the help!!!

author: patb
author_rank: Regular Contributor
timestamp: July 21, 2011, 10:28:36 am
content: I just wanted to share some bad news reagarding my 3-weeks old EX430. It is broken. Rotary switch is malfunctioning and DMM can now only measure V and u/m/A. No matter what you select on "green" scale it always switches to V mode. And no, it didn't fall from my desk. In fact I didn't use it for days. I have no idea what happened. What a crap.Anyway, it seems that Extech has some serious problems with QA. I remember Dave's test of EX505 (part of 100$ shootout) and they actually sold unit with broken PCB (patched with wire!). My confidence in Extech products has just started to vanish.

author: saturation
author_rank: Super Contributor
timestamp: July 21, 2011, 11:02:29 am
content: Sorry to hear. It would pay now to open it and check the rotary switch, maybe there is just some debris in the connectors. Take photos and post if you can.Quote from: patb on July 21, 2011, 10:28:36 am

author: patb
author_rank: Regular Contributor
timestamp: July 21, 2011, 11:51:29 am
content: Yeah, I've just opened it and took some photos. It seems that the problem is with upper contacts on the rotary switch (see last photos). Not only they seem to be broken (especially the one at the top - not really reliable construction imho), but they seem to be oxidized (not so shiny as the other ones). I am also concerned about all those screws that go directly into the plastic case. This will wear off very fast (I can feel it already).The good news is that after putting it all together it works again.My advice: avoid pushing rotary switch. It seems that this mechanism is rather fragile.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 21, 2011, 05:04:24 pm
content: Quote from: patb on July 21, 2011, 11:51:29 amI can not imagine how you can push one rotary switch, but this can be only me.Even so, if you had to push it, because you was thinking, that it would improve the contact of it with the PCB,this was a wrong idea, all that it needs are some fast motion,about 3-4 times forth-word and backward movements, and it will be fine.If you do have oxidized contacts, email Extech about the problem and report back in this thread with their answer.I would like to know if they will react with professionalism,and send back to you, one new range switch free of charge.

author: patb
author_rank: Regular Contributor
timestamp: July 21, 2011, 05:50:32 pm
content: Quote from: Kiriakos-GR on July 21, 2011, 05:04:24 pmHehe, no, I didn't push it to "solve" my problem. If you look at the picture above with the contacts you will notice that one part of the upper contact slipped from the plastic. It was probably caused by force applied to rotary switch (my guess). That's why I wrote advice to avoid "pushing" the switch. Just rotate it.Quote from: Kiriakos-GR on July 21, 2011, 05:04:24 pmMaybe I will. Especially if my DMM starts to behave badly again.Right now it works just fine.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 21, 2011, 10:49:17 pm
content: If there is an oxidized contact in there you should replace the range switch.Or else the contact will damage the PCB.About your pictures I can not see them, your files its too large for internet use.And at my current internet connection, I get charged by the bandwidth that I use.Next time make them 800X600.

author: Vancata
author_rank: Contributor
timestamp: April 29, 2014, 09:32:21 pm
content: Hey folks, can anyone give me a boost on that IC that i circled with red on the uploaded photo. Just want to repair the Hz and C measurment system on the multimeter, so i can have all properly working. The IC kidna smoked out and don't see any numbers. Was thinking it might be some opamp like the TL062 at the bottom (the other 8pin smd packet). Any ideas? Seems this is the first revision of the board, it have later one with kinda other IC's packets there.

author: kc9qvl
author_rank: Regular Contributor
timestamp: April 29, 2014, 10:14:31 pm
content: Any numbers on it. Hard to tell from picture but looks like has something on it.

author: Vancata
author_rank: Contributor
timestamp: April 30, 2014, 03:08:40 am
content: Quote from: kc9qvl on April 29, 2014, 10:14:31 pmActually this is not the real picture of the board. Just random one from the net, will upload mine, but it is 1:1 as this one. No part number is visible, the chip die made hole to the plastic cover of the IC. Can't see any marking even with the magnifying glass.edit: Well just cleaned it good and found out this was some kind of hard dirt and the IC is okey, seems i won't be able to repair the C and Hz ranges at all. Some more deep problem accure, will just check the few voltage regulators and will call it off.edit 2: Need some fixed voltage regulators datesheets: First one is "3A OK" and the other one "5A 57". Really don't know how to read this codes, just traced out one the regulators from the capacity and Hz common pad and measured and on the output pin it give short to ground, so i guess either its not a voltage regulator or i have short somewhere after it.

author: janoc
author_rank: Super Contributor
timestamp: April 30, 2014, 09:16:46 pm
content: Quote from: patb on July 21, 2011, 10:28:36 amI have two Extechs 470 and one has a similar problem with the range switch - when you press on the switch, the meter goes completely gaga and shows nonsense on the display. Actually, I think it isn't even the switch itself, because I took it apart, cleaned everything (the problem is intermittent), but the issue is still there. Probably a cold/cracked joint somewhere that manifests itself when pressure is appliedAlso meter new from the box, the seller sent me the other one which so far works (apart for the temperature range measuring high) for free as a replacement.Got a Brymen instead and the Extechs are collecting dust.

author: Vancata
author_rank: Contributor
timestamp: May 01, 2014, 05:37:19 am
content: Yeap, kinda found the same thing here. Seems its not the rotary switch but most like a cold joint appeared somewhere on the board. Might try the oven or just go for other meter for HV stuffs I'm testing.