Sorry for the multiple posts, but more ideas coming to me now after a little break.
Does your meter show 0L or open circuit with probes removed in following scenarios?
1) manual 400 ohm range
2) manual 4k ohm range
3) manual 40k ohm range
4) manual 400k ohm range
5) manual 4M ohm range
6) manual 40M ohm range
I will check al these things wednesday or thursday, I have a pretty tough exam thursday
so I will see when I have time !
I will check al these things wednesday or thursday, I have a pretty tough exam thursday so I will see when I have time !
Okay. Good luck on your exam. Maybe after a couple day break, the answer to this problem will become obvious to me or someone else reading this thread. Posting your findings on Friday is good as well.
It seems that there is a short between R7 and R8(?). What happens if you separate them?
Argh! too slow
It seems that there is a short between R7 and R8(?). What happens if you separate them?
Argh! too slow
At least your photo shows a better angle than mine. BTW, if even that doesn't solve the problem, it is a representation of CEM Instruments assembly quality. Or lack of it.
Hmm, it could be nothing, but R7 and R8 in your picture look like they are touching? Circled in red.
If they are touching, separate them slightly. I don't think this will solve the ohms problem, however.
I alo noticed and seperated them but no improvement
Can you replicate the two readings in this thread
https://www.eevblog.com/forum/repair/fluke-89-iv-powers-up-measures-nothing/msg956417/#msg956417
I only need pictures #2 (1354) and #3 (1355) replicated. Your Dad's Fluke = Fluke 77 III and your Velleman = 187.
Here are my measurements:
RANGE FLUKE
auto 148k1
0,145V
0,22mA
000,0R 38k26
0,369V
0,23mA
0,000k 38k26
0,369V
0,22mA
00,00k 18k49
0,145V
0,05mA
000,0k 7k51
0,020V
0,02mA
0,000M 5k9
0,002V
0,01mA
00,00M 5k73
0,2mV
0,01mA
Can we also get a picture of the pcb with the LCD removed? It looks like you need to remove the 4 screws to release the LCD. With all the bodges, let's see if there is anything interesting there?
Here is a high quality picture :
I did remove the LCD and boy is it a mess
! I tought some solderpoints were bad, but this takes the cake
.
Might as well clean it up a little,€5 Velleman to the to the rescue
!
Well it isn't perfect, but a lot cleaner than before, sadly the problem isn't gone
What a mess!
The yellow cable looks very strange. They cut the GND plane and replaced it with the wire. It seems they had a offset voltage to compensate. Can you check if the cable at the damaged place is a) still insulated and b) still conductive from one end to the other?
What a mess!
The yellow cable looks very strange. They cut the GND plane and replaced it with the wire. It seems they had a offset voltage to compensate. Can you check if the cable at the damaged place is a) still insulated and b) still conductive from one end to the other?
As bad as that cable looks, its still okay
Wow. I've never seen a mess that bad even inside a Hazard Fraught freebie.
This is a complete stab in the dark, but if you look around the board you should find some transistors, usually NPN, with the B-C terminals shorted. These are used as voltage clamps in various places by taking advantage of the reverse avalanche property of the E-B junction. Check their B-E junctions and make sure they act like diodes. Keep in mind you may find transistors in normal configuration, or dual-diode arrays also in SOT-23 packages, ignore them.
Don't get caught up with this awesomely-manufactured meter and forget to study for the exam.
Don't get caught up with this awesomely-manufactured meter and forget to study for the exam.
I couldn't really concentrate knowing that my poor little meter is waiting for some troubleshooting
This is a complete stab in the dark, but if you look around the board you should find some transistors, usually NPN, with the B-C terminals shorted. These are used as voltage clamps in various places by taking advantage of the reverse avalanche property of the E-B junction. Check their B-E junctions and make sure they act like diodes. Keep in mind you may find transistors in normal configuration, or dual-diode arrays also in SOT-23 packages, ignore them.
I will certainly give this a shot
When you have time, I would like to get some more data points.
We know the meter doesn't show open circuit, but does show 0.0 when the probes are shorted. If you have a decade resistor box or some resistors, I would like to try one resistor for each range.
For example, measure a 100 ohm resistor in the 400 ohm range, a 1k ohm resistor in the 4k ohm range, etc. It doesn't have to be 100 ohm, just something between 1 and 399 ohm.