BM235 defective?

[retiredcaps]

I measured the voltage on the BM235 Diode function as 3.25V and on the Ohms function as 1.7V.

@Dr.Joe, Are you getting these voltage readings from the BM235 using another DMM? 

In addition, does capacitance work at all say measuring a 1000uF capacitor?

[retiredcaps]

@Dr.Joe. One more thing.  Does temperature work?

[retiredcaps]

R25 looks a bit weird and i can't get a solid measurement for it. Jumps around a lot, but that could be my cheapie DMM.
Edit: could the unstable measurement be because im measuring in circuit?

In Dave's video, R25 is marked as 103 which is a 10k ohm resistor.  If your measurement is not stable, it possible that other components are affecting the reading (like C25)

[retiredcaps]

R32 (next to the big 10megohm resistor) looks a lot like R25, but measures &stable at 49.8kOhms.

What is the marking on R32?

edit: Found some high resolution photos from Dave at

https://www.flickr.com/photos/eevblog/24180623623/sizes/o/

R32 is 223, a 22k ohm resistor.

[Dr.Joe]

@retiredcaps:

Temperature does work, i can' test the other functions right now because i want to keep the soldering on this thing to a minimum.

As far as i can tell, R32 and R25 have no markings on them. All the other resistors do.

R32 is definitely not 22k on my meter.

[BurningTantalum]

OK Kean- Silly me... You got me there !
Dr Joe- Now I see...

BT

[Dr.Joe]

Backside looks okay, so does the range switch.

I think i will replace R25 and R32 with the values from Daves picture and Video. 

[retiredcaps]

I think i will replace R25 and R32 with the values from Daves picture and Video. 

Before you change those resistors, what about those voltage measurements in post #25 and capacitance?  The more we know what works and doesn't work will narrow down the problem.

[Dr.Joe]

Sorry, i was out of counry  on a business trip.

@retiredcaps: sure.

Continuity works, and i can measure a stable 1.628V between the input jack. It just doesn't display a ohms value

Temperature works as well at a stable 0.908V.

Capacitance doesnt work at all, when i put any capacitor across the probes, the meter switches to "----nF" and has 1.4mV across the probes.

Diode Tester does not work, but has stable 3.104V between the probes.

Edit: So far, i have only resoldered L3, all the other beads check out fine. R25 and R32 look a bit weird. i have not resolderd or reflowed those.

Now Ohms: Doesn't work, and the weird part is: Voltage across the probes starts at around 60mV, then goes up to about 350mV, then my cheap DMM (4000 Count i presume?) autoranges, and i get the reading of about 1,47V for a fraction of a second, before it starts at 60mV again. this whole cycle takes about a second.

Edit: A/mA DC range also not working. Shows O.L on both ranges with about 100mA going through the meter.

[PedroDaGr8]

Forgive me if I am stepping on toes but is Dave not taking care of this? Are you just trying to fix it for fun? Not implying that Dave is intending to avoid his duties, just curious on why all the work when an RMA might be more appropriate.

[Dr.Joe]

Dave has been well aware of this, in fact I contacted him before I opened this thread.

if this was a 5 minute fix like the other one in his video, it would have been stupid to send it back to Australia, let Dave repair it and let him pay for return shipping. Also, i don't want to pay custom twice for the same product. avoiding that is a bit of a headache with german customs.

[jitter]

Forgive me if I am stepping on toes but is Dave not taking care of this? Are you just trying to fix it for fun? Not implying that Dave is intending to avoid his duties, just curious on why all the work when an RMA might be more appropriate.

Perhaps the "Waranty void when seal broken"-seal is broken? 

Edit:

Dave has been well aware of this, in fact I contacted him before I opened this thread.

if this was a 5 minute fix like the other one in his video, it would have been stupid to send it back to Australia, let Dave repair it and let him pay for return shipping. Also, i don't want to pay custom twice for the same product. avoiding that is a bit of a headache with german customs.

Good reasons and good to know it's with permission...

[retiredcaps]

Now Ohms: Doesn't work, and the weird part is: Voltage across the probes starts at around 60mV, then goes up to about 350mV, then my cheap DMM (4000 Count i presume?) autoranges, and i get the reading of about 1,47V for a fraction of a second, before it starts at 60mV again. this whole cycle takes about a second.

Edit: A/mA DC range also not working. Shows O.L on both ranges with about 100mA going through the meter.

Hmm, the results above, in addition, with all the other data so far does not bode well.  I'm thinking something is wrong with the main IC, but I still may be missing something?  All your input protection checks out okay.

Let me think this for a bit longer.

PS. Wrt to your cheap DMM, put it into manual range mode (4V) and then it shouldn't have to autorange and might work faster to get a more accurate reading. Maybe retest with it in manual range?

[retiredcaps]

Right now, I don't have any more ideas, but I will re-read and re-analyze all the data again.  I might have missed something really obvious?

If there are no more suggestions from members, you may need to contact Dave and get a replacement meter.  You may want to wait until Sunday night to make a final decision. Maybe during the weekend, some other members can offer help or have more time to look at this?

I don't know how Dave handles the return costs and shipping charges.  Good luck with customs (again).  I know it can be frustrating.

It is funny how it can pass calibration, but fail immediately after being shipped.  I mean, some of the functions don't even work at all like current.

[ez24]

It is funny how it can pass calibration, but fail immediately after being shipped.  I mean, some of the functions don't even work at all like current.

It is a physical problem - right?  So being shipped will break something lose.  Not funny but physics, right?  What I wonder is what does future mold changes mean.  Does this mean when the current molds wear out?

[imidis]

looking at the pics, how does the solder join on Q9 look? I notice it's a little crooked and looks like the solder is a little sparse.

[retiredcaps]

It is a physical problem - right?  So being shipped will break something lose.  Not funny but physics, right? 

I don't know if it is phyiscal or not.  OP has already resoldered L3.  There could be another dodgy soldered component? Micro crack on the pcb?

OP says DCV, continuity and temperature work fine, but ohms, capacitance and current does not.  While continuity works, OP says there is no reading on the screen, just 0L.

[retiredcaps]

Not funny but physics, right?

On a lighter and completely true note, I have no idea how I passed that year long course in University. 

[kolbep]

Maybe that inductor that you resoldered has some damage inside still.
Just bridge across it to see if that does anything.

[Kleinstein]

+ 1 to bridging L3 for a test. Form Daves repair thread is seem there is a mechanical weakness in the area of L3 and L2. So it's likely not bad soldering, but just the mechanical load that causes the solder to fail. It's well possible the part itself has a micro-crack and soldering did not really fix it.

For passing calibration, the damage might well occur during shipping, from vibration or temperature.

It's rather unlikely, but the broken part could have defeated some input protection, so that there is a slight chance to have a follow up error, maybe from ESD. A partial reverse engineering of that area might exclude this.