Troubleshoot M92A Multimeter

[haseeb]

Hi Guys,

Is there any body who knows about the multimeter Model M92A.

I am having a problem with ma functionality of my multimeter.

Any body has the schematics for this model.

I am attaching the device picture the right side device in the picture is my model.

Regards,
Haseeb

 

[Mooly]

Hi,
If it's just the ma range I would guess at either an internal fuse, open circuit shunt resistors or open circuit print in that order.
What have you been measuring

 

[lcsaszar]

These little bastards can be very easily destroyed by meausuring voltage when the DMM is in resistance setting. Fortunately, replacing the 7106 chip generally cures the problem.

 

[Minion]

Also in case you didn"t know , some multimeters have the Probes going into different holes for the Ma Function.... At least mine does...


Cheers

 

[haseeb]

Thanks guys for responding.

I was actually measuring the tail current in the input stage of my power amp project.

I checked the fuse and it is fine.

mooly: can you please eloborate "open circuit shunt resistors "


oshifis : I did not check what chips my multimeter has but I'll check and try to replace, if it is the same.

oshifs , will my Ampere fuctionality still be available?, if 7106 chip gets blown ...

 

[lcsaszar]

Haseeb,

If only the mA is wrong, but resistance and voltage is OK, then the chip is good. Maybe one of the current sensing precision resistors is broken. You need another DMM to measure them one by one.

BTW, the 7106 chip (originally coming from Intersil as ICL7106) has many different names with the same pinout and functionality. They are interchangeable, regardless what is printed on them. Maxim also produces it.

 

[Mooly]

Hi,
A DVM is really just a millivolt-meter. When you measure current you are actually measuring the volt drop across a known resistor- the shunt resistor - and there will be a few of these selected by the function switch, depending on what range you are on.
See www.kitsrus.com/pdf/7106.pdf for a data sheet.
If all other ranges work I would have thought the 7106 would be O.K.

 

[haseeb]

Guys thanks for the suggessions and inputs.

I will post once after my findings and troubleshoot.

Regards,
Haseeb

 

[haseeb]

Guys,

I could not figure out the fault in my device.

Every thing looks fine, I did not dare to do RND on this because only problem with my device is ma functionality else every thing is fine Ampere,ohm,volts etc.

I tried to figure out the pcb components routed through the ma connector,but the traces were rounted almost all board.

decided to keep quit until I loose all the functionality of my meter.

Regards,
Haseeb

 

[Zen Mod]

silly I know , but - did you checked the fuse ( if any is present inside ) ?

 

[haseeb]

Fuse do exists and it is just fine.

 

[lcsaszar]

Maybe this description is of any use for you. Refer to Fig.4 and top of page 26 (Amps Section troubleshooting).

http://www.cleanfuelcellenergy.com/m-2666k.pdf

 

[haseeb]

Hi oshifis,

Thanks lot for the doc.

My meter looks similar ,I have to cross check with the doc and get back to you.

Thanks for the efforts.

Regards,
Haseeb