Finally , i can take out selector with lock cone-shaped . Selector switch stack with 3 item , copper blade, linear switch for AC DC Ohm , and Base Plastic Cover with External Retaining Rings. Correct way to take apart it's push down plastic with copper blade to release cone-shaped lock nut.
replacing lots of original parts with new ones may result in losses in precision.
instead, simply inserting a Constant-Current-Source with Enable-Switch seems more suitable.
btw, for led selecting, I use this kind of 'led tester' :
Yes, when meter sold out from factory , i am sure its have gap between copper spring selector and linear switch for AC DC Ohm . But The firts owner MF10 take apart and when recontruction dont remember make a gap . If switch dont have gap when turn round nut to lock , its will be lock and very hard to take apart !
I think gap around 2mm its correct . can make gap by plastic rule with slot have 6mm wide.
replacing lots of original parts with new ones may result in losses in preci ...
Led tester its only example for easy understand about test semiconductor N-P join . With 3v we can easy see larger angle of pointer , and read resistor in two-way , Resistor in Forward Bias Anh Reverse Bias.
Its a same like IV curver diode
I allway prefer analog meter have high voltage like
3+9V ( MF47F change to 3v)
1.5+ 15V ( MF10 - MF35)
1.5+ 15V + 15V ( MF 96 VP )
3 + 22.5V ( Hioki As-100d )
With high voltage and small current in x100k range , we have higher resolution in LI ( 1ua/ line / 50 line face meter )
Im totally complete agree event 22.5v its fade diagnostic because leak current will increase when increase voltage test ( good conditon like 1N4007 have 1-10ua leak when test over 1000v reverse bias ). But in case its good componant , if componant failure i think can easy see with resolution around 1uA / Div when reverse bias
chihaxinh 发表于 2024-1-17 09:41
Led tester its only example for easy understand about test semiconductor N-P join . With 3v we can ...
led tester is an application of constant current source (CCS), with maximum voltage of 9V.
using it with a voltmeter, it is possible to drive loads up to 9V with limited current.
besides possible over voltage damages, a 9V CCS looks better than 3V one.
this comes the idea that adding a CCS to the original voltmeter.
unlike led tester, any maximum voltage above 3V is acceptable.
Almost of Chinese 1.5v analogue meter have the scale of not being read Li/Lv easily.some of American 1.5v analogue meter have the scale which read Li/Lv easily
I finish modifier following your guide .
Step 1 : prepare 3 resistor - 33K 47K 10K
prepare one pot wirewound 10k replace orginal 12K
Change following schematic below . And have problem when short Red - Black probe in Ohm mode - MOving of pointer very strong - and cannot turn to zero ohm ! This is problem . How to fix that
I dont have battery 3v in hand , so i temporary using 14500 lithium battery in case.
Note: I recheck schematic so problem like i missing one more battery 15v . In this case schematic using 2 battery 15v - total 30V for 100k and 3V for below 100k
IP卡
狗仔卡
发表于 2024-1-16 22:48:54
，我没有拆得这么彻底。
显身卡
楼主
。
