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Problem with multimeter DT9205A

Automatics

Oct 3, 2021
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Oct 3, 2021
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The problem is when it is on continuity mode on the display shows reading 393 beeper still works but I cant test leds. On 20kΩ/200kΩ display shows 2.40/02.4. The problems appear when accidentally when it was on continuity mode my dad used it in a 220 AC curcuit. I opened it but didn't saw any obvious damages. Any idea how can I fix it or what is wrong with it. Thanks!
 

Automatics

Oct 3, 2021
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Oct 3, 2021
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Yeah I know I can buy new one cheap but I was wondering if someone had an idea what could be
 

Allen Bong

Dec 5, 2014
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Dec 5, 2014
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Here is the schematic of your digital meter meter...

Since you said that your dad connected the probe to AC on the continuity test mode, I'd check all the components connected to point "J" like ptc1 and ptc2, 900K and 100K resistors etc.. IC2b and IC2c (LM324) are probably also gone as well.

dt9205a_excel_multimeter_sch.jpg
 

Riyadh1959

Oct 22, 2021
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Oct 22, 2021
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Hi every one

The problem is when it is on continuity mode on the display shows reading 180 beeper still works but I cant test leds. On 20kΩ/200kΩ display shows 2.40/02.4 . Any idea how can I fix it or what is wrong with it. Thanks!
 

73's de Edd

Aug 21, 2015
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Riyadh1959 . . . . . . is you also being . . . . . . Automatics . . . . . . .or has he permanently left the arena . . . . .along with Elvis ?
 

73's de Edd

Aug 21, 2015
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We know that . . .that's understandable, BECAUSE the diode test function has BLOWN UP ancillary parts within it and 240mv is borderline of being able to light up even the lowest threshold of LED . . . the RED LED.
Come back with the requested functionality and accuracy test of the voltmeter portion of the unit.
 

Automatics

Oct 3, 2021
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Oct 3, 2021
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Try the voltmeter functions and see how accurate they are.
The AC is ok it shows accurate, the DC is accurate as well. The ohms readings are off whithout anything connected it shows 2.34K and on continuity it shows 399 whitout to be connected to anything but it beeps when it is shorted
 

73's de Edd

Aug 21, 2015
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The problems appear when accidentally when it was on continuity mode my dad used it in a 220 AC curcuit. I opened it but didn't SEE any obvious damages.
I fully suspect, that with the meter being set down on a low ohms test function, such that the rotary switching done by the dial, was setting down near and engaging the R7-R6-R5 divider resistors . . . . that the bottom left corners Q1 . . . 2N9014 . . . . was also ZAPPED with that OVER voltage , so change it out.
If physically having room enough, a conventional short leaded . . . . . those ends bent into L's . . . . . TO-92 cased version could be used .
Or actually, any generic 2N3900-2222-4400 series transistors as subs , as its actually being used in a diode function.
 
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