A more reliable replacement for Brymen BM869S?

[andrejr]

I've had the Brymen BM869S since 2016, bought on the recommendation of this very forum, and it's served me well. I used it very carefully, for low voltages mostly 99% of the time, and was quite satisfied.

However, recently, anything AC (voltage, frequency, current mA and A) stopped working, and I need to find a replacement. I used practically all of the meter's functions, some to a lesser extent (% for 4-20mA I used maybe twice).

What would be a worthy replacement? I don't mind if it's a bit more expensive, and I would be very happy if it was physically smaller (my main complaint for the 869s, except for the newly found unreliability).

[coromonadalix]

surely something happened to render this meter unreliable .... in ac  not dc ?  your story seem incomplete ?

since it still work in dc ...


well you have the 7xx series  who came out ...

[andrejr]

It's a true RMS meter, with an AD636 RMS-to-DC converter. I'm guessing that either that died, or the surrounding circuitry (passives + tl062s). But, you know, that's very hard to fix when you don't have a working meter to do it, right? Besides, that chip's no longer produced, so I can only buy it for ~25eur on shady Ebay listings, who knows what I'll get. I guess I'll try fixing it, when I get another, more reliable, meter.

As for what killed it, zero clue. I was diagnosing some old audio mixer, quite low voltage (+-18V, +48V phantom, 230V supply), just checking voltages (not currents). The meter worked fine. The next day I wanted to continue, and the meter was dead. It was never exposed to any abuse, just low voltage stuff with an occasional SMPS PSU diagnostic, way below its max ratings. I rarely used the current modes (maybe 10 times total) and never came even close to blowing fuses. I have a strong feeling that the meter dying is purely because of its inherent faults (when you search online, I'm not the first with this issue), and in no way because of a hard life or plain misuse. I used the meter once or twice a month, really.

[KungFuJosh]

I know this sounds dumb, but... Have you checked the fuses?

[andrejr]

Of course I did, with my shitty little yellow meter I got in elementary school 20 years ago that somehow still works. Both fuses are completely fine. No scorched or overheating (I have an IR camera) components inside either, and a new battery doesn't help.

[KungFuJosh]

Have you tried banging it against the table or a wall?

[andrejr]

Have you tried banging it against the table or a wall?

Hah, of course I did. Also freezing the insides w/ computer duster upside down. Didn't help.

[KungFuJosh]

Percussive maintenance! Hit it harder! 😉

[andrejr]

Btw this is what happens when you switch it to any AC mode with nothing connected (actually, whatever you connect), it goes through the ranges and ends up in O.L. Also, DC measurements are quite slow.

https://imgur.com/a/RyZX1iG

[pope]

Have you tried banging it against the table or a wall?

Hah, of course I did. Also freezing the insides w/ computer duster upside down. Didn't help.

I can;t be of any help but it's the first time hearing about freezing the insides. What's the reason behind it?

[andrejr]

Finding broken solder joints and / or bond wire joints through thermal shock; also works for cracks in resistors and similar. Of course, helps detect thermal effects of any kind.

[KungFuJosh]

Did you test the fuses for continuity, or did you also check resistance value? Have you checked the fusible resistors?

[mwb1100]

I used practically all of the meter's functions, some to a lesser extent (% for 4-20mA I used maybe twice).

If you use nearly all of the functions on the BM869s you might want to consider buying another in spite of the 6 year lifespan for this particular one.  Even buying a second  (maybe even third)  BM869s will be less of an outlay than one  similarly spec'ed Fluke.

But if the experience has soured you on Brymen, you might look at Fluke 287/289 if the display isn't too slow for your tastes.  Hioki meters seem to be to be well regarded here (though I have no experience with them).  The DT4281/DT4282 appear to have a similar feature set to the BM869s. 

[Fungus]

Did you test the fuses for continuity, or did you also check resistance value? Have you checked the fusible resistors?

Fuses won't affect voltage in any way.

[joeqsmith]

I've had the Brymen BM869S since 2016, bought on the recommendation of this very forum, and it's served me well. I used it very carefully, for low voltages mostly 99% of the time, and was quite satisfied.

However, recently, anything AC (voltage, frequency, current mA and A) stopped working, and I need to find a replacement. I used practically all of the meter's functions, some to a lesser extent (% for 4-20mA I used maybe twice).

What would be a worthy replacement? I don't mind if it's a bit more expensive, and I would be very happy if it was physically smaller (my main complaint for the 869s, except for the newly found unreliability).

That's too bad.  I bought my first one in 2015.  Brymen provided me a second one in 2018 that I have used for several destructive tests.  I'm still frequently using both meters.   I've looked for something brand new that I like more than the BM869s but haven't come across anything yet.  Keep us posted on what you end up with. 
 

[KungFuJosh]

Did you test the fuses for continuity, or did you also check resistance value? Have you checked the fusible resistors?

Fuses won't affect voltage in any way.

They will if they're bad.

[joeqsmith]

Did you test the fuses for continuity, or did you also check resistance value? Have you checked the fusible resistors?

Fuses won't affect voltage in any way.

They will if they're bad.

Why?

[KungFuJosh]

Did you test the fuses for continuity, or did you also check resistance value? Have you checked the fusible resistors?

Fuses won't affect voltage in any way.

They will if they're bad.

Why?

Possibly related from the manual:

If the instrument voltage-resistance input terminal has subjected to high voltage transient (caused by lightning or switching surge to the system) by accident or abnormal conditions of operation, the series fusible resistors will be blown off (become high impedance) like fuses to protect the user and the instrument. Most measuring functions through this terminal will then be open circuit. The series fusible resistors and the sparkgaps (or varistors) should then be replaced by qualified technician.

I've seen a couple handheld meters with fuses that weren't exactly blown that did weird stuff that sounds similar to what he described. I know it's rare and weird, but weirder things have happened. Okay, it was the same meter twice, but it was still the fuses.

[bdunham7]

Even if you expand the term "fuses" to include the surge resistors, I don't think that there are any in this meter that would blow and cause only an AC problem let alone the type of AC problem we're looking at here.  A problem in the TRMS converter circuit does seem pretty likely, although perhaps there is some way a switch contact could cause this.

The AD636 is only obsolete in the TO-100 package and is still available in the CDIP variety AFAIK for about $50.  The choice of TO-100 here seems pretty bizarre as there are much higher precision--and older--designs using the CDIP variety.  Do the later model 869S use a different TRMS converter?  It's probably not cost effective to replace the AD636 as they're expensive, that may not be the problem and even if it is, there are no available calibration instructions for this meter and recalibration would most certainly be required.

As far as replacing it, if you want that same or better feature set for a good price it might make sense just to buy a new one of the same model. 

[J-R]

I completely recommend pulling this apart and inspecting everything.  PCB, switch contacts, etc..  Apply a voltage to the input and trace it as far as you can.  Check the converter supply voltage and input/output.  What have you to lose at this point?

Side note, the calibration procedure is known for the BM869s:  https://web.archive.org/web/20241001203742/https://www.jackenhack.com/calibrating-brymen-bm-series-multimeter/
However, you'd obviously need a bit of additional equipment, so I'm just posting this for completeness.

Brymen reliability is not really the issue here, it's the warranty.  To keep costs and corporate liabilities down, coverage is limited.  For the price point, it's a popular trade-off for buyers.


The BM789 doesn't have the dual display or computer interface, but otherwise is probably considered an equal of sorts to the BM869s, just different in some areas.

Also, it seems Fungus is too tired to join in, so I'll just do him a favor and point out that he'd suggest the BM859s.

Ultimately, if you really liked all of the aspects of the BM869s, then I echo the sentiment of just getting another one.  You could keep the broken one as a parts unit.  Fuses, input jacks, display, rubber case, etc. could all be handy to have some decades down the road.

[bdunham7]

A few general follow-up points:

Great seeing someone has figure out the calibration procedure, but the meter has 4 internal physical adjustments, 3 capacitive trimmers and 1 trimpot and I think they are all involved with either the TRMS conversion circuit or the AC input dividers.  The trimpot is likely the TRMS converter scale offset trim.  I suppose that part could be figured out as well.  Actually, upon reflection that's probably a job for me if anyone needs help with that. 

Apparently the AD636JHZ (TO-100 hermetic package) is still available at some level, just not through normal distributors anymore.  There are thousands available but not in quantities of one or two--Rochester wants about $350 shipped for a 10-pack.  Based on recent teardown photos it appears that Brymen is still using that package even today.

[joeqsmith]

If the instrument voltage-resistance input terminal has subjected to high voltage transient (caused by lightning or switching surge to the system) by accident or abnormal conditions of operation, the series fusible resistors will be blown off (become high impedance) like fuses to protect the user and the instrument. Most measuring functions through this terminal will then be open circuit. The series fusible resistors and the sparkgaps (or varistors) should then be replaced by qualified technician.

Carefully read your post.  These are not fuses but fusible resistors. As the manual suggests, once they open, not only would ACV be effected but also DCV and pretty much every thing else.  Consider the amount of transients I have ran on the BM869s, I have never damaged the resistors mentioned.   The talk about lightning or surge being a possible cause.  Also, how other parts should be replaced if these were damaged.     Also note, these resistors are not in series with the current inputs.

[andrejr]

I looked into the Hiokis and they seem like an especially bad deal: only 3 years of warranty, double the price of Brymen. Brymen has 1 year of warranty.

I could maybe get a used Fluke for 400, but who knows if the warranty is transferrable and how much of it is left.

[andrejr]

I completely recommend pulling this apart and inspecting everything.  PCB, switch contacts, etc..  Apply a voltage to the input and trace it as far as you can.  Check the converter supply voltage and input/output.  What have you to lose at this point?

Side note, the calibration procedure is known for the BM869s:  https://web.archive.org/web/20241001203742/https://www.jackenhack.com/calibrating-brymen-bm-series-multimeter/
However, you'd obviously need a bit of additional equipment, so I'm just posting this for completeness.

Brymen reliability is not really the issue here, it's the warranty.  To keep costs and corporate liabilities down, coverage is limited.  For the price point, it's a popular trade-off for buyers.


The BM789 doesn't have the dual display or computer interface, but otherwise is probably considered an equal of sorts to the BM869s, just different in some areas.

Also, it seems Fungus is too tired to join in, so I'll just do him a favor and point out that he'd suggest the BM859s.

Ultimately, if you really liked all of the aspects of the BM869s, then I echo the sentiment of just getting another one.  You could keep the broken one as a parts unit.  Fuses, input jacks, display, rubber case, etc. could all be handy to have some decades down the road.

I did all I could do with a shitty yellow meter, but I stopped myself before I wasted any more time, because I'm a grownup now. Since it's not the switch or anything, it's a circuit problem, and I know I can't really fix that.

Why? Because if I do, I'll have to cal it, and I don't have any calibration equipment, nor friends with a PPM fetish and metrology equipment. I don't plan to pick up a metrology hobby. I also live in Slovenia, a small country with a very small market - this means that any "specialist" services like calibration or similar are more expensive than, say, in LA or NY or London, for what's likely terrible service. Calibrating the meter would likely be more expensive than buying a new one.

Summing all this up, I think that just buying another 869 is probably the fiscally soundest decision, even though I hate the fact I'm buying a known-unreliable meter.

[Fungus]

I looked into the Hiokis and they seem like an especially bad deal: only 3 years of warranty, double the price of Brymen. Brymen has 1 year of warranty.

Hioki are one of the best brands.

I could maybe get a used Fluke for 400, but who knows if the warranty is transferrable and how much of it is left.

I don't get how you can think Hioki is expensive but a $400 used Fluke is good value. They're both in the "luxury" class and not good bang per buck.

You could get two Brymens for that much money.

I don't know why your meter failed but Brymen's as reliable as any other brand, even Fluke.

... it seems Fungus is too tired to join in, so I'll just do him a favor and point out that he'd suggest the BM859s.

BM857s - I'll take the simplified selector dial over the temperature measurement. 

These are Brymen's "industrial" meters and they're quite a lot smaller then the BM869. More boxy and square. The screen isn't as exposed. If you want something really small though you'll have to go with something like the BM235, I don't know if it meets your needs.

They don't have dual display but having that on 100% of the time seems like clutter to me. Your AC is very unlikely to be anything else than 50/60Hz anyway. The rest of the specs aren't very different than the BM869s.