repairing the DT830B digital multimeter

[kavish]

can any body help me..when i using multimeter a kind of spark have been seen inside. when i opened the case i found that two SMD registor are damaged. what can i do to repair it . i have dt830d DMM

 

[JimB]

Kavish,
Post your question ONCE.
Not three times.

JimB

 

[kavish]

Kavish,
Post your question ONCE.
Not three times.

JimB

sry sir..that was my mistake..

 

[absf]

Take a good & clear picture and mark the resistors which were sparked .....

Allen

 

[kavish]

Take a good & clear picture and mark the resistors which were sparked .....

Allen

 

[kavish]

Kavish,
Post your question ONCE.
Not three times.

JimB

 

[absf]

I believe the 2 blown resistors are R7 and R8 in the schematic attached.

I guess you must have measured high voltage using the mA current range OR you are measuring voltage using the 10A and COM inputs. That's why the fuse is blown off instantly. In the fuse position you can solder a piece of fine copper wire e.g. 32 SWG. Put back the battery and see if the LCD still able to display anything. If not, I guess the 7106 chip is toasted and it's not worth your effort repairing it.

If the LCD does show something then test it with the DC and Ohm range and see if it works correctly. Only then replace R17 and R18, probably 1Ω and 9Ω resistors.

Allen

 

[kavish]

I believe the 2 blown resistors are R7 and R8 in the schematic attached.

View attachment 91268

I guess you must have measured high voltage using the mA current range OR you are measuring voltage using the 10A and COM inputs. That's why the fuse is blown off instantly. In the fuse position you can solder a piece of fine copper wire e.g. 32 SWG. Put back the battery and see if the LCD still able to display anything. If not, I guess the 7106 chip is toasted and it's not worth your effort repairing it.

If the LCD does show something then test it with the DC and Ohm range and see if it works correctly. Only then replace R17 and R18, probably 1Ω and 9Ω resistors.

Allen

thanks for your help sir ,
but even the fuse it not there the multimeter is in working condition but when i measured a 1.2v dc battery with multimeter it shows abt 9.4v . and same when i measuerd 1k reg. i shows abt 58 or someting ,hence my MMR is not working properly. i dont know wats going on..!! (i have not installed fuse and reg.17 and 18 yet.).!

 

[kavish]

what is the value of r17 and r18 in above multimeter...?

 

[kavish]

I believe the 2 blown resistors are R7 and R8 in the schematic attached.

View attachment 91268

I guess you must have measured high voltage using the mA current range OR you are measuring voltage using the 10A and COM inputs. That's why the fuse is blown off instantly. In the fuse position you can solder a piece of fine copper wire e.g. 32 SWG. Put back the battery and see if the LCD still able to display anything. If not, I guess the 7106 chip is toasted and it's not worth your effort repairing it.

If the LCD does show something then test it with the DC and Ohm range and see if it works correctly. Only then replace R17 and R18, probably 1Ω and 9Ω resistors.

Allen

thanks for your help sir ,
but even the fuse it not there the multimeter is in working condition but when i measured a 1.2v dc battery with multimeter it shows abt 9.4v . and same when i measuerd 1k reg. i shows abt 58 or someting ,hence my MMR is not working properly. i dont know wats going on..!! (i have not installed fuse and reg.17 and 18 yet.).!

 

[JimB]

when i using multimeter a kind of spark have been seen inside.

What were you doing when the spark was seen inside?

By best guess is that your meter is now scrap, beyond economical repair, and should be replaced by a new one which works.

JimB

 

[kavish]

What were you doing when the spark was seen inside?

By best guess is that your meter is now scrap, beyond economical repair, and should be replaced by a new one which works.

JimB

i was measuring voltage by mistake i switch the knob over resistance range..

 

[Tony Stewart]

did you try to adjust the trimpot?

It seems to be rotated to the end or past it.

Does the chip get warm? then it's toast.