Digital Multimeter Repaired
Some days ago I got unhappy because my Digital Multimeter (DMM) suddenly stopped working. What was the complaint? It did not switch on. I own an Analog Multimeter, but I prefer the DMM.
As you can see it’s a DT9205A, and it was bought from the HUNTER store in my country last year. I talked to a colleague who has a similar (same model) and his DMM had happened the same situation a some time ago, he told me he had exchanged the switch button for the Data hold button.
I said to him: no, I’m going to repair the switch button. So I began to disarm my DMM, 3 screws in the back cover plus one in the battery cover.
Next step was to separate the PCB, only 6 screws.
As I do not have a handy de-soldering tool I used a traditional method in my country to extract the switch from the PCB: the injection needle (look at the photos below). In other words, heating the solder point and push down the needle to separate the tin from the tip of the component
Why did not I use a vacuum de-soldering pump? Because the rails of this area in the PCB were very thin and I was afraid of destroying them.
Look at the result then.
The switch was extracted from the PCB.
It was disarmed into pieces, for clean and lubricates it. Finally it was armed again. Look at the photos below.
All the contacts (fixed and mobile ones) were cleaned with a piece of paper and lubricated with “3 in 1” lubricating oil.
When the switch was re-soldered in the PCB and the device was armed, look at the result when it was switched on.
I tested my DMM in the different scales and for showing some of these tests; I took photos when I was testing the resistors supplied with my Blue ESR Meter: 82 Ω and 5.6 Ohm for alignment.
I could not deny I was very happy now; my own DMM was safe and done now.
This article was prepared for you by Humberto Rodriguez, one of our ‘Master Authors’ from Cuba.
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Anwar Shiekh
March 6, 2015 at 10:00 pm
I often find it is enough to spray some silicone oil into the offending switch.
Humberto
March 6, 2015 at 11:59 pm
Yes, I had done this some months ago, so it was time to repair the Switch Button.
Renato P. Estopace
March 10, 2015 at 7:21 am
Thanks for the very informative post, i have the same type of meter also but problem is erroneous reading on ohms X1 scale, a few months ago I have set it to this range but have accidentally measured a voltage reading. I am still troubleshooting for the possible problem. More power Sir.
Merlin Marquardt
March 6, 2015 at 10:31 pm
Very good.
Humberto
March 7, 2015 at 12:29 am
Thanks Merlin
Andre Gopee
March 6, 2015 at 10:39 pm
Good Job Humberto... another one saved for the trash. Keep up the good work. By the way nice technique with the needle.
Humberto
March 7, 2015 at 12:47 am
Thanks, the needle technique is very commom in my country. I learned it exactly in 1988, and I've been using it from then.
Anthony
March 7, 2015 at 2:05 am
Thanks for sharing this story and the photos Humberto. Very helpful !
Robert Calk
March 7, 2015 at 2:31 am
Good job Humberto. That is a poorly built DMM and I wouldn't trust it with much voltage or current.
Humberto
March 9, 2015 at 7:41 pm
Hi Robert, I know you are right. I'm saving money to buy a UNI-T one, do you or anyone here know about this brand?
Robert Calk
March 10, 2015 at 10:50 am
Some of them are built poorly also. I heard that the Uni-T 139C is built well, if I remember right. You can ask on forums and see which are built well and good for electronics.
Robert Calk
March 10, 2015 at 7:11 pm
I just bought a UT 139C from Frankie at his Ebay store here -
http://www.ebay.com/itm/Uni-T-UT139C-True-RMS-Digital-Multimeter-with-Temperature-NCV-Backlight-/171213085325
I need another DMM anyway, so I will let you know how well it is built.
Robert Calk
March 21, 2015 at 5:01 am
I just received the DMM today. It is a very well built meter for $50US. The NCV(non-contact voltage) is pretty handy also. It has good ceramic fuses and input protection. Also, you can change the batteries(2 AA's)without removing the whole back off of it.
Nice meter for the price.
Robert Calk
March 27, 2015 at 5:14 pm
Hi Humberto,
The meter also has a great latching continuity tester. I was really shocked at how good it is. Mine outputs a nice clean voltage of 1.002V that could be used for a voltage reference for checking other meters on the quick. It also defaults to DC. The only thing I don't like about my Fluke 87V is that it defaults to AC.
mahmoud_tajpour
March 7, 2015 at 4:07 am
you did very good technique with needle.
Humberto
March 9, 2015 at 8:56 pm
Thanks
Mark
March 7, 2015 at 6:02 am
Hey Humberto,
Thanks for your article.
I wish my multimeter is that easy to repair! I damaged it the other day and am a little unsure about where to start as I don't have a schematic.
Robert Calk
March 11, 2015 at 11:58 am
I would start with any wiring connections making sure they are good and the wires also. Then check for bad solder joints and broken PCB traces. Then start checking components starting with any transistors, caps, diodes, and resistors.
Gerald
March 7, 2015 at 10:40 am
Nice job Humberto. I find the needle technique really cool...
Cheers,
Gerald
Humberto
March 10, 2015 at 7:17 pm
Thanks Mr. Gerald. I've been reading your articles and they are really interesting with scientific explanations. Have a good day.
Yogesh Panchal
March 7, 2015 at 1:06 pm
Dear Humberto,
Nice fix, can you make a video about injection needle using for this process and share it on blog? or just explain what is the process.
Robert Calk
March 7, 2015 at 9:46 pm
I agree with Yogesh - that would be a good article.
Humberto
March 10, 2015 at 7:06 pm
Ok, I'll prepare a video asap with detailed explanation
Biruk aweke
March 7, 2015 at 2:39 pm
very nice MR.and thanks for sharing.
Yogesh Panchal
March 8, 2015 at 10:41 pm
Dear Humberto,
Please provide us injection needle SIZE / NO. if available.
Lee
March 9, 2015 at 12:54 am
Very interesting that Needle Technique, never heard of it 🙂
Do you have various needles diameters each de-soldering job ?
tawanda
March 9, 2015 at 4:18 pm
thanks man
Tito
March 10, 2015 at 1:12 am
Good job Humberto,I had also the same problem with the cheap China DMM.
sam montero
March 11, 2015 at 11:55 pm
hi
I already have a sanwa dvm. but still I bought the same model as yours. The reason is that its cheap and I could mesure capacitance with it.
Also if ever I make a mistake and destroyed it, no problem. This also has a problem with the switch. I was able to get a replacement but the pins is not an exact configuration and have to rewire the clading.
Sam
mike retz
March 17, 2015 at 3:17 pm
VERY SATISFIED
Khanh
December 25, 2015 at 5:36 pm
Please help me, my dt9205a didn't work in AC voltage and capacitor meters
Would you like to show me how to fit it, thank you so much!
rajkumar
April 28, 2016 at 12:28 am
i have dt9205a+ multimeter. the display of the meter is broken and does not work. is it possible to change the display?
if yes please tell me where can i buy the display.
otim brian
January 7, 2017 at 10:53 pm
my dt9205a is nt reading capacitance yet its new.wat could be de problem
Mina
March 12, 2017 at 11:42 pm
i have a problem with my dt9205a
display -1 all time and i don't know what i do to fix this problem please help me
Muti
December 4, 2017 at 2:14 am
Dear Humberto,
Hope you are healty and enjoying. I am opened my DT9205A (the same as in this article) but I loosened all screws. The results now I don't know correct positions of six copper brushes under the selection switch. Can you help? I need some one to show pictures of working selector switch with correct copper brushes underneath. Wish I read your great article before opening mine. Thanking you in advance. Hoping for some reply soon.
Muti
December 5, 2017 at 1:05 am
Kindly also send pictures of selector switch copper slider brushes.
I am also checking this page in Hope of reply. Thank you.
mehdi
October 25, 2018 at 8:58 am
hi
i have a DMM like above pic named dt9250a but the selectors pins going to pieces and being apart and know selectors don't work for me please sent me a photo of bake of selector for resorting those pins and placing pins correctly so I need a photo of bake of selector for viewing the arrangements of selector pins.
with best regards
Mehdi
Adeleye Ayodeji
December 9, 2022 at 8:17 pm
I like your idea and the way of approach
Adeleye Ayodeji
December 9, 2022 at 8:22 pm
I have similar multimeter like your own, the problem with it is that it doesn't give correct measurements both in resistance, voltage etc,even in all ranges.Pls what can l do