Author Topic: HIOKI Analog Multimeter M-230A, need help with restoration & resistor values  (Read 4459 times)

0 Members and 1 Guest are viewing this topic.

Offline zaokaTopic starter

  • Frequent Contributor
  • **
  • Posts: 379
  • Country: us
This is HIOKI M-230A analog multimeter, one of the best meters at that time, discontinued about 35 years ago. It has burned resistors in x1 and x10 OHM ranges.

I contacted HIOKI in Japan and they only had schematic without resistor values...

If somebody has this model or its user manual I would love to get these values and to fix it for my collection.
 

Offline grenert

  • Frequent Contributor
  • **
  • Posts: 449
Could you calculate it from values for other ranges?  Use a resistor substitution box and try different value to see what works.
 

Offline zaokaTopic starter

  • Frequent Contributor
  • **
  • Posts: 379
  • Country: us
How?

R21, 25 and 26 are defective.

R21 is probably 14R, its value measure 13.54R (I can see brown, yellow on resistor)
R26 is burned, however, it measures 8.54R, this is that big resistor with wire on it.

So the question is what is the value of R25?

Other resistors are the following:

R18 = 94.9K
R19 = 5.00K
R20 = 200R
R22 = 3.53K
R23 = 7.41K
R24 = 749R
R27 = 26K
VR5 = 10K
B2 = 9V battery
 

Offline SeanB

  • Super Contributor
  • ***
  • Posts: 16386
  • Country: za
Post the scematic, then we can get probable values for the CBB resistors. For the cooked well one try to read the resistance from the remaining cap to the carbon film in the middle, try to get it at the middle of the spiral for each half. That will then give an idea of the value of the complete unit. Tip for reading the carbon it to take a piece of copper wire 2.5mm and sand the one end to form a flat surface to better contact the carbon film.
 

Offline zaokaTopic starter

  • Frequent Contributor
  • **
  • Posts: 379
  • Country: us
I posted schematic, here it is again...

Tried reading resistor, it does not ready anything, its completely burned.. it is that resistor at the bottom of the picture.
 

Offline grenert

  • Frequent Contributor
  • **
  • Posts: 449
Since the lower ohms ranges just have smaller resistors to send more current through, a ballpark estimate for R25 would be about 75 ohms, about ten times less than the resistor for the X100 range.
 

Offline zaokaTopic starter

  • Frequent Contributor
  • **
  • Posts: 379
  • Country: us
Installed 75R and it works, its not perfectly accurate, however, it needs calibration first.

Now I have to take it a part and clean everything including selector switch contacts and replace some wires that corroded.

If anybody come across this model please take a picture of the board and post so we know the real values that HIOKI used.

 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf