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simpson analog meter wont zero up

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Bmerboy98

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My simpson meter ..its a 260 (yellow case) analog meter

doesn't zero up on ohms function ,,the needle reading stays towards the center of the scale and cant be zeroed up on the ohms function..batteries, fuses have been replaced ..

the needle goes to zero on voltage scales

could be a resistor? but i have no idea which one to replace to correct this

Meters are used to teach children and i have several with this problem so help would be greatly appreciated



thanks
 
Post a schematic; it could be an open resistor or bad solder joint.
 
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My simpson meter ..its a 260 analog meter

I know one of the list guys (many perhaps?) is the proud owner of a Simpson 260. Perhaps he'll chime in...

You say you replaced the battery. Did you actually measure to make sure it was good?
 
im going to try another d battery tomorow...

the problem is that the needle reads to abt 1/3 of the scale and stays there on any ohms scale
 
My simpson meter ..its a 260 (yellow case) analog meter

doesn't zero up on ohms function ,,the needle reading stays towards the center of the scale and cant be zeroed up on the ohms function..batteries, fuses have been replaced ..

the needle goes to zero on voltage scales

could be a resistor? but i have no idea which one to replace to correct this

Meters are used to teach children and i have several with this problem so help would be greatly appreciated



thanks


Check the resistor in series with the Ohms zero trim pot, sounds like it has changed value. You might be able to experiment and find the correct value. Or measure it on a good meter. These two resistors are the only ones that docent change when you change resistor ranges, so it stands to reason that it might be the problem.
 
Hi Bmerboy98,

There seem to be a lot of versions of the Simpson 260
but I found one with a yellow case and there's a
schematic at page 32 of the manual.

on1aag.
 

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  • 260-8Ximan.pdf
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Did you change both batteries? On some of the older Simpsons, the 9V battery is very similar in size and shape to a "C" cell. You may have to adapt the connections to the modern 9V battery
 
According the schematic the same battery is used for the Rx1 and Rx100 scale, so see if you also have zeroing trouble on the Rx100 scale.
Does the meter work on other ranges?
The 1.5v batt. neg. goes to the meter movement negative through R2. I'd first look at the value of R16. This 11 ohm resistor corresponds to the center reading of 12 ohms.
The only other resistors involved in Rx1 are R17-R21. If you take readings in this network we can probably troubleshoot it down to a single resistor.

With a 50 uA meter at 250mV the movement itself is 5kohm.
 
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Every Simpson Analog Meter that had this symptom was the same problem.

Bad batteries!..double check the batteries.....both of them!

If those are OK, did a student perhaps mess with the meter zero adjust. It is the plastic, slotted screw in the center of the lower part of the meter movement itself. My son mesed with mine once many years ago drove mu nuts for about an hour.

If these don't fix the problem, time to open it up and check it against the schematic.
 
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