Troubleshoot M92A Multimeter

haseeb · 30th May 2008, 05:45 AM

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 · 30th May 2008, 11:32 AM

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

oshifis · 30th May 2008, 12:05 PM

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 · 30th May 2008, 04:06 PM

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 · 3rd June 2008, 01:49 AM

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 ...

oshifis · 3rd June 2008, 06:19 AM

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 · 3rd June 2008, 06:26 AM

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 · 3rd June 2008, 09:27 AM

Guys thanks for the suggessions and inputs.

I will post once after my findings and troubleshoot.

Regards,
Haseeb

haseeb · 4th June 2008, 04:55 AM

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 · 4th June 2008, 07:54 AM

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

4th June 2008, 07:54 AM	#10
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	silly I know , but - did you checked the fuse ( if any is present inside ) ? __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

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30th May 2008, 11:32 AM	#2
Mooly diyAudio Member Join Date: Sep 2007	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

30th May 2008, 12:05 PM	#3
oshifis diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	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.

30th May 2008, 04:06 PM	#4
Minion diyAudio Member Join Date: May 2006	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

3rd June 2008, 01:49 AM	#5
haseeb diyAudio Member Join Date: Feb 2008	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 ...

3rd June 2008, 06:19 AM	#6
oshifis diyAudio Member Join Date: Mar 2004 Location: Budapest, Hungary	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.

3rd June 2008, 06:26 AM	#7
Mooly diyAudio Member Join Date: Sep 2007	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.

3rd June 2008, 09:27 AM	#8
haseeb diyAudio Member Join Date: Feb 2008	Guys thanks for the suggessions and inputs. I will post once after my findings and troubleshoot. Regards, Haseeb

4th June 2008, 04:55 AM	#9
haseeb diyAudio Member Join Date: Feb 2008	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

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