Brymen BM235 InEr issue - Page 1
Forum section: electronics / testgear

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 11:52:23 am
content: Hello! I have a Brymen BM235 multimeter that worked very well for over 5 years, but as of lately I keep getting InEr error and beep from multimeter even when the probes are not connected. I saw here some threads where it says that is an issue with the firmware, where if you put the switch in Auto LoZ and then quickly move it to another position, the message InEr appears for a second. Mine does this also but the InEr message appears even if i move the switch from Off position to Volts or Ohms. It stays for a second and that's it. I thought it's a problem with the traces on the board and opened it up and checked. The board was a little dirty, I cleaned it with alcohol and greased the traces. I put the board back and after powering it up, I had InEr error message displayed on every position of the switch, with the probes disconnected. After a few cycles of power up and shut down, the error disappeared and hasn't come up since then. I made a photo of the board and uploaded it here. You can see there are two traces that have the green paint washed off of them. Could this be the problem and if it is, how can I fix it?Thank you.

author: sonpul
author_rank: Regular Contributor
timestamp: July 28, 2024, 12:45:09 pm
content: If you put the selector on A ; mA or uA is also displayed by InEr? If yes, then you need to check the sockets, in them the contact is divided into two independent parts, a short circuit or leakage is possible.

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 01:31:11 pm
content: Thank you for the reply. The InEr message and beep was present on all positions of the switch, but like I said, after a few On/Off switches, it went back to normal. I also cleaned the sockets and checked them for short-circuit and they are fine. The multimeter works now and the issue didn't manifest itself. But I wonder what caused the issue and maybe there are users here that had this problem and find a fix for it.

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 01:37:09 pm
content: This is a closeup of the traces where the green paint is faded

author: Fungus
author_rank: Super Contributor
timestamp: July 28, 2024, 03:16:45 pm
content: Quote from: Sebaxtian on July 28, 2024, 01:37:09 pmCalling joesmith...Are they they really relying on solder mask to prevent the switch from making contact? That doesn't seem believable to me.

author: ebastler
author_rank: Super Contributor
timestamp: July 28, 2024, 03:27:14 pm
content: Quote from: Fungus on July 28, 2024, 03:16:45 pmMaybe it does not matter whether or not the switch contacts the trace in that position, since other contacts remain open? They could easily have routed the connecting trace differently if this were critical.What has me wondering more is that lonesome piece of trace on the inner circle at. approx. the 8 'o clock position, which is apparently not connected to anything. Did that tear off from the main trace at some point?Edit: Annotated picture added. The trace fragment in the black circle is the one that has me wondering.

author: TomKatt
author_rank: Frequent Contributor
timestamp: July 28, 2024, 03:42:15 pm
content: Quote from: ebastler on July 28, 2024, 03:27:14 pmIsn’t that a few via holes to the other side?

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 03:52:45 pm
content: That piece seems is in the right place, doesn't wiggle or anything and I didn't found any loose pieces when I took the multimeter apart. Hopefully this issue is not present in the BM789 version, because I just order it, exactly prior to this one giving out errors. Maybe this is a sign...

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 03:55:50 pm
content: That small piece doesn't have a connection/hole to the other layer of the board

author: ebastler
author_rank: Super Contributor
timestamp: July 28, 2024, 03:59:32 pm
content: Ok, that lonely piece of trace is also visible in Dave's teardown (6:34 timestamp):But the marks on the green soldermask are much less pronounced, if they are present at all.

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 04:34:39 pm
content: Quote from: ebastler on July 28, 2024, 03:59:32 pmMaybe it hasn't been used as much as mine.

author: Fungus
author_rank: Super Contributor
timestamp: July 28, 2024, 04:56:30 pm
content: Quote from: ebastler on July 28, 2024, 03:27:14 pmI guess not. The switches make contact between adjacent tracks so if both contacts touch the same track, that's OK and if there's nothing to the side then that's OK too. Contact pairs circled below.It just looks bad...

author: floobydust
author_rank: Super Contributor
timestamp: July 28, 2024, 05:13:47 pm
content: OP I would clean the inside of the banana jacks. Jack detect is a high impedance circuit using the half-shells and any leakage currents there between them will give troubles.I use IPA on a Q-tip and stuff it in there, give it a spin to clean out crud, then let it dry out. One of yours (V?) looks black at the top compared to the others, so might be grease or oxide something from your test leads contaminating them.The two-pin header to the jack board has the mA, A jack detect signal. Make sure it's clean on the jack board as well.The Brymen rotary switch I think is a poor design. It shows amateur PCB layout and the wiper is cave man tech, I think they could do much better. It also shows in new models if you look at the traces there, a few mistakes.

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 05:43:12 pm
content: Quote from: floobydust on July 28, 2024, 05:13:47 pmI already cleaned the banana jacks with IPA and checked the continuity on the split banana jacks, and it was ok.

author: floobydust
author_rank: Super Contributor
timestamp: July 28, 2024, 05:55:16 pm
content: It seemed to get worse after you took it apart and cleaned it, then got better, is that right? I think it just needed to dry off, some IPA has added water.What lube did you use on the rotary switch? That topic will start another war here. How did the rotor wipers look, I use a paper swipe to clean it.I thought they used mineral oil on the PCB. I use DeOxit F5 with PPE with no problems, although it has little lubricant in it.Grease is a bit much - lithium salts conduct a little, silicone grease reacts with nearby components.I thought the BM235 has had issues with the rotary switch needing a spacer, and the input jacks might crack. Not sure but just to alert that it could be a mechanical problem.

author: Sebaxtian
author_rank: Newbie
timestamp: July 28, 2024, 06:05:59 pm
content: Quote from: floobydust on July 28, 2024, 05:55:16 pmAfter the cleaning, the board had enough time to dry, more than half an hour, so I think that wasn’t a problem. To grease the traces I used some grease from the rotary switch, I took a bit from there and spread it on the board, I used just a bit.

author: J-R
author_rank: Super Contributor
timestamp: July 28, 2024, 08:39:28 pm
content: Based on the information provided, my 2 cents is that this was only an input jack contamination issue. The bottom of the jack can collect quite a bit of environmental junk as well as metal shavings, and the delay after cleaning seems reasonable. Further flushing/cleaning might be a good idea. And of course both the A and mA uA jacks are able to contribute to the issue.Are those traces partially worn through or is it just the coating?I'm firmly in the add lubricant to contacts camp after taking apart a few DMMs and seeing the shocking amount of wear and metal dust. I used SuperLube a couple times and never had any issues, but now I think I've settled on CRC 2-26.Either way, I just apply tiny amounts to only the wear points and it really smooths the selector operation. My perspective is I'd rather have to clean dried gunk off a board 20 years from now instead of trying to recreate worn contacts/traces.

author: TnF
author_rank: Contributor
timestamp: April 29, 2025, 07:06:28 am
content: BIG STORY short, mine, a BM319s (which is similar in construction to BM235) i had from 2016, just randomly developed "InEr" in a ranges a few days ago. I disassembled, didn't find anything, cleaned the jacks multiple times, followed the jack detection trace and didn't find any issues.Reading the comments from the recent Dave's video regarding little residual flux from manufacturing getting conductive with time, i put it inside my resin 3d print washer full of Isopropyl alcohol, 15min wash each side, then used a hairdryer on hot, problem FIXED!Just leaving this here for others to find if they get the same problem.

author: Kean
author_rank: Unknown
timestamp: April 29, 2025, 07:19:26 am
content: I have recently seen this issue intermittently on one of my three BM235's.The LCD was also randomly fading in & out and the error went away again after I touched the batteries, so I suspect it is time to change them even if no low battery indication.Interestingly it is also the last one I bought which also probably gets the least use, so that also makes me suspect the batteries as the other two I use more have certainly had new batteries recently.If it keeps happening with new batteries then I'll certainly try washing the PCB as well, and re-lubricating the switch contacts.

author: TnF
author_rank: Contributor
timestamp: April 29, 2025, 09:01:09 am
content: Quote from: Kean on April 29, 2025, 07:19:26 amI did try that during my troubleshooting with fresh new alkaline batteries (so proper 1.5V*2), no difference in my case. I always keep the meter at home, and in fact i did use it just fine just a week before. The theory is that the detection circuit is very sensitive and if a thin layer of flux re-crystalizes and is conductive enough it will not be visible by naked eye. That would be the only simple logical reason the wash fixed it. Also it's been a 3 days since i've fixed it, and re-checked operation is normal still, so the problem didn't re-occur after.

author: Kean
author_rank: Unknown
timestamp: April 29, 2025, 09:51:32 am
content: Well I went to use that BM235 again and I got an immediate InErr and dim display, then the DMM died completely!I checked the batteries and they were at 1.56V. I think I must have changed them when it first happened earlier this month. Anyway, I tried another set of batteries just in case, and then cleaned the battery contacts (no visible corrosion) and PCB battery contacts. Neither helped.I noticed that a bit of pressure near the display sometimes made it power on for a moment, and sometimes after putting the back on again with selector on V that I could get a short burst of life. I then noticed that the battery contact springs were splayed out just a bit, so I bent them back straight and after reassembly it is working again. Apparently the slightly splayed battery contacts were not reliably making contact, and depending on slight pressure or bumping the case it would sometimes work, sometimes not.So something extra to keep an eye out for, especially if seeing the InErr message along with a dim display but good batteries.

author: Antrus
author_rank: Contributor
timestamp: April 30, 2025, 03:13:24 pm
content: I wonder if Fluke had such widespread problems? Is it so difficult to choose the right flux?

author: bingo600
author_rank: Super Contributor
timestamp: April 30, 2025, 04:52:55 pm
content: My 257 won't display DC Voltage.The BAR display just fluctuates, and no voltage is shown..If i switch range, it starts to show 0.0v , but still no real voltage will be shownEverything else seems to workIt showed after 3..4 months of no use.It hasn't seen much use , but is some years old.I can't be sure if it didn't have discharged batteries at some point.Never seen such an issue on my other meters.I'll NOT be buying Brymen again.

author: J-R
author_rank: Super Contributor
timestamp: May 01, 2025, 12:02:07 am
content: Definitely worth opening up the BM257 to check for any damage, cracked solder joints, flaky selector contacts, battery corrosion, etc. and etc.There are plenty of happy Brymen customers, but also you have to consider these units to be mostly disposable, since they are not economically repairable and also contain proprietary ICs flashed at the factory.