Extech 505 falling apart - Page 1
Forum section: electronics / testgear

author: elettroluis
author_rank: Contributor
timestamp: November 26, 2018, 10:36:01 pm
content: Hi thereSome years ago I bought an Extech 505. First thing I noticed was the fact the test leads were requiring some effort to be inserted.I thought maybe that was because it was supposed to be an IP67 (waterproof) instrument. Well "they certainly thought of that and it's normal" I thought.OK. I treated it well, I have seldomly used it since 90% of the time I use an ancient Fluke which is working flawlessly from the day I bought it or a more recent Brymen.Today when I inserted a test lead in the COM, the internal cylinder collapsed.I opened it up and what I saw ... I never saw before.All 4 the plastic cylinders containing the 4 metal ones are BROKEN IN TWO. All 4.Please see the images.I never hammered the test leads inside, I have used it with care like I ever did with all my gear in my life, but honestly this time my first thought when I opened it was to throw it out of the window in disgust.Also the rotary selector never worked well after 6 months from the date of purchase.Never had a multimeter falling to pieces like this in my life.Any suggestions to fix it in some way ?Thanks.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 26, 2018, 10:50:18 pm
content: Wow! Not a cheap meter either. You have other meters, time to just let it go.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: November 26, 2018, 10:57:46 pm
content: I just wonder: is the shunt supposed to look like this? It looks like it was ripped apart by alien metal mites and soldered together again.

author: edpalmer42
author_rank: Super Contributor
timestamp: November 26, 2018, 11:09:42 pm
content: Whatever you used to glue the cylinders back together wouldn't be strong enough to take the forces that caused the break in the first case. Maybe find some tough plastic rods that you could glue onto the inside of the back of the meter that would push against the four nuts. Or plastic cylinders that would press fit onto the nuts and push against the back. That way, any forces would be transferred to the back which would either be on the bench or in your hand. So, the repaired parts wouldn't have to absorb those forces.I also noticed that weird shunt. Hell of a way to adjust it - cut it part way through with wire cutters?? Multiple times???Ed

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 27, 2018, 12:48:03 am
content: It looks as if the metal connecting strips are just a bit to long for the plastic cylinders.That would put stress on them causing them to eventually tear.Can you easily press them back in place?If you can find a proper glue for the plastic used then you could glue them back together.Then add some washers or bend the connecting strips a bit so they exert less force.Or drill out the existing cylinders to make room for new panel mount sockets.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 27, 2018, 02:48:24 am
content: Wow, I never saw that one coming. I used epoxy on my rotary switch to repair the plastic. Roughed it up with some sand paper first. These, being right at the front and of the meter, I'm not so sure it would be a good idea to even try and repair it. I had a case that may have worked that I recycled the plastic or I could have sent it to you.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 27, 2018, 06:03:57 am
content: Quote from: elettroluis on November 26, 2018, 10:36:01 pmDid you buy your meter before or after seeing Dave's $99 shootout? The build quality, or lack of it, is consistent with what others have reported.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 27, 2018, 06:07:03 am
content: Quote from: 0xdeadbeef on November 26, 2018, 10:57:46 pmYes, that is a representative sample from CEM Instruments.See other examples athttps://www.eevblog.com/forum/testgear/teardown-extech-ex570-my-first-but-also-last-extech/http://mrmodemhead.com/blog/gallery/craftsman-82003/

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2018, 07:30:51 am
content: Quote from: 0xdeadbeef on November 26, 2018, 10:57:46 pmYep, that's the calibration. They make them so then the resistance is a bit low then "bite" them with cuttters, increasing the resistance until it meets spec.

author: Terry01
author_rank: Frequent Contributor
timestamp: November 27, 2018, 04:43:35 pm
content: I had a EX505 that I ended up selling as I got better meters. I really liked it as a meter but it was quite a bit off on most ranges. It was a weird meter for sure!If I remember correctly temperature and uA were the only two things it measured accurately and the rest of the ranges were off anything from a bit to miles! It never broke though.I did burst a couple fuses in it measuring on the wrong ranges and stuff but it held strong!Hope you get yours fixed buddy.

author: TurboTom
author_rank: Super Contributor
timestamp: November 27, 2018, 05:27:15 pm
content: Quote from: retiredcaps on November 27, 2018, 06:07:03 amIn CEM's defense I've got to say that theOEM DT-989 (by PeakTech)is of fairly decent build quality which has also been confirmed in Mike's teardown video:Mike's teardown video.So at least certain models appear not to be pestered by the proverbial "CEM crap quality"... Maybe, they improved their quality control recently?

author: joeqsmith
author_rank: Super Contributor
timestamp: November 27, 2018, 06:11:40 pm
content: My daily meter for the last seven years has been an Extech EX540 which is a re-branded CEM DT9939.It is calibrated (Not Aligned!!) annually. Last year I brought it home to show how far it was out. I loaned it out once to a person who managed to turn the knob past the dead stop which is why I had to epoxy it back together. Beyond people blowing a few fuses in it as well, I havn't had any troubles with it.That said I bought one that I think someone had previously bought for a review and returned it. It was missing screws. Someone damaged the cable for the RF link. I doubt this was CEM's handy work.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: November 27, 2018, 06:24:56 pm
content: Errm, OK, if this is true, it seems like a somewhat down-to-earth approach to calibration. I guess the solder on top means they cut off a bit too much then...Quote from: Fungus on November 27, 2018, 07:30:51 am

author: joeqsmith
author_rank: Super Contributor
timestamp: November 27, 2018, 06:28:43 pm
content: It's true. Seen similar crimps on several meters I have looked at. You can see them under the tape on several of these.https://youtu.be/ne4Ls2mPF-s

author: elettroluis
author_rank: Contributor
timestamp: November 27, 2018, 08:18:28 pm
content: Hi guys, thank you for the replies.Quote from: GreyWoolfe on November 26, 2018, 10:50:18 pmNot particularly cheap, no, and nothing like that ever happened to me even with cheap meters.Quote from: edpalmer42 on November 26, 2018, 11:09:42 pmThanks for the suggestion: I thought about something like that, it's not easy because the contour of the plastic shell is very irregular. Where there are the upper two holes for the leads there is the battery compartment, where there are the two lower holes there is a sloping profile (see the picture) so it's quite difficult to shape whatever you want to put inside to follow that profile with a tight fit.For now I glued back the 4 plastic cylinders, now I'm doing some experiments with various stuff (high density insulation material which can be bent and shaped, plastic rods, etc.)Quote from: Terry01 on November 27, 2018, 04:43:35 pmI don't have high hopes but I'm gonna to give it a try.Quote from: retiredcaps on November 27, 2018, 06:03:57 amI didn't see the video at all, thank you for the link.This passage is really making me laugh considering what just happened to mine:https://youtu.be/n3WGaiYF2sk?t=2360Maybe something happened to just some units when they cooked the plastic and it's not representative of every unit... but... the PCB broken track in Dave's video is not representative, my broken input jacks are not representative... uhm.... I have some legitimate doubts now.Quote from: joeqsmith on November 27, 2018, 02:48:24 amThat would have been awesome, thank you for the thought anywayPS: about the shunt, some have already answered. I wasn't 100% sure but that was my idea too. I saw BIG shunts where some metal was literally sawed off to get to the right resistance. So I thought this was something like that.If I can get something out of this broken mess I'll post an update.

author: edpalmer42
author_rank: Super Contributor
timestamp: November 27, 2018, 08:40:07 pm
content: Can you buy epoxy putty in Italy? Here in North America it's available at every hardware store. Use it to fill the area inside the back, push everything together, then take it apart and let the epoxy cure. Should give you a perfect fit. If necessary, put something like plastic food wrap over the putty to keep it from sticking to the nuts.Ed

author: elettroluis
author_rank: Contributor
timestamp: November 27, 2018, 09:04:30 pm
content: Quote from: edpalmer42 on November 27, 2018, 08:40:07 pmUhmm... I'm not sure what it should be exactly. Is it a bi-component adhesive ? So you have two blobs to mix into a bigger blob an then apply or is it already ready to use ?As long as it's not going to glue all togetherDo you have a link of the product you have in mind ?

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2018, 09:08:25 pm
content: Quote from: elettroluis on November 27, 2018, 09:04:30 pmYes.

author: edpalmer42
author_rank: Super Contributor
timestamp: November 27, 2018, 09:38:50 pm
content: Quote from: elettroluis on November 27, 2018, 09:04:30 pmI just searched ebay.it for 'epoxy putty' and got 19 hits that ship from Italy. You'd probably get more if you used Italian instead of English. I don't think it would matter what brand you bought - you just want to fill up the empty space in the back so that the nuts will press on the epoxy. You could use regular epoxy if you set up a dam to keep the epoxy from flowing away from where you want it. I noticed that some epoxy putties are reinforced with steel. You obviously don't want to use one of those!!Ed

author: Fungus
author_rank: Super Contributor
timestamp: November 28, 2018, 07:32:58 am
content: Quote from: edpalmer42 on November 27, 2018, 09:38:50 pmHere in Spain it's called "masilla epoxi"Quote from: edpalmer42 on November 27, 2018, 09:38:50 pmYou can also reinforce it with fiberglass, eg.:https://www.ebay.es/itm/162587851817

author: joeqsmith
author_rank: Super Contributor
timestamp: November 28, 2018, 03:13:42 pm
content: Rough up the posts with the fiberglass and maybe use some shrink tube over that to tighten it down to the post while it cures? I may be thin enough to fit through the board. The leads on these do fit tight. Maybe the rubber got hard over the years, coupled with a little added persuasion.I did post about the two Extechs I have. It's amazing how inconsistent their manufacturing is.https://www.eevblog.com/forum/testgear/a-tale-of-two-meters/

author: elettroluis
author_rank: Contributor
timestamp: November 28, 2018, 03:20:46 pm
content: Well, I have "fixed" it.Thank you for all the suggestions, for now I tried with the things I had available at home, I'll consider the epoxy sarcophagus in case this will fail.First of all I glued back the cylinders, I used some glue in excess and then pressed hard to get a good match of the surfaces and fill the pockets of air with a very thin layer of glue, the excess just dropped outside.I used some hard (very hard, they were really hard to cut) plastic rollers I took from the mechanics of a VHS tape, I kept a lot of these plastic and metallic cylinders, because "I'm sure these could become useful one day or another".I made two of them sloping down to accommodate the respective slope in the shell, and I put two soft gummy feet on the top of the other two to get a perfect fit because it was difficult to reach that by just removing material from the two half rollers.I put the rollers on one at the time, tried the shell on, removed some material, repeated until ok. Then I moved to the next one.The diameter of the rollers was just slightly too tight to fit around the nuts, so I've used some hot air (a desoldering air gun) to help them fit.As long as I was doing this I cleaned up the rotary switch and resoldered 4 cold-looking joints.I tried inserting and removing the test leads 20 times and all seems to work well for now. It's even smoother than before for some reason.Well, this is probably not going to win a prize for the best repairing effort but it seems ok.I'll let you know here if this fails in time.Luis

author: joeqsmith
author_rank: Super Contributor
timestamp: November 28, 2018, 03:27:05 pm
content: Seems as good as anything else. Even if the glue cracks, the case should do a fine job holding things together.