Fluke 325 clamp meter DC amps not working - need schematic or service manual

[srmahaffy]

I bought a used Fluke 325 Clamp meter, and the DC amp setting displays -113 amps without being connected to anything. It will also not zero out. Any help is appreciated. Looking for schematic, service manual, or pics of PCB front and back. Also, when inspecting my meter, I notice five missing parts that are capacitors and resistors, but I don’t know if they are not there because of the PCB being used for other models of clamp meters. Any help is most appreciated!!!

[m k]

How are other modes measuring?

[HighVoltage]

If AC current measurement is working and DC current is not, I would start the with the Hall sensor and its circuit.

[srmahaffy]

Thank you for your inputs it is appreciated!
Where is the Hall effect sensor? How do I check that?

Here are the modes of the meter that work:
Resistance
Capacitance
AC voltage
DC voltage

What doesn’t work:
AC current
DC current
DC current zero
(Maybe) frequency

Also, I want to mention when I received the meter, the display was installed upside down, which was an easy fix to rotate 180 degrees. It was also missing a screw that holds the upper part of the housing together, (no big deal). I had a spare fluke screw that I purchased on eBay, which worked fine. The calibration decal cover is missing also.

Question: Does anyone know how to check the ribbon cable end that connects to the clamp end of the meter?

I’ll post some pics

[srmahaffy]

Pic 1

[srmahaffy]

Pic 2

[srmahaffy]

Pic 3

[srmahaffy]

Pic 4

[srmahaffy]

Pic 5

[m k]

Have you checked inside the clamp that all parts are present and correctly positioned?
It seems that previous assembler has had some problems.

Hall effect sensor is an active component so it must be powered.
AC side can be just a transformer.
No idea what else can be connected to those 8 pins, maybe a cable connected loop.

[srmahaffy]

Hi M K,
I didn’t open up the clamp part of the meter, as it seems like the case is glued together (??)
Any thoughts about that? I’m not experienced with clamp meters, but have repaired a few other Fluke meters, like an 87V, 87Iii, and a minor repair on a 233.

I want to share with everyone that someone on eBay sent me a pic today of the back view of a 325 PCB with the selector switch assembly still on, and my 325 looks the same as far as that view. Theirs also had the same missing parts as mine that I can see.

[m k]

SIP sensor can also be incorrectly oriented.

Since the range is 400A clamp connection should have 2 voltages.
When you disconnect the clamp one voltage should disappear, that is probably hall effect input.

You can then test the circuit with simple voltage divider and see different values.

A sensor example
https://www.allegromicro.com/en/products/sense/linear-and-angular-position/linear-position-sensor-ics/a1324-5-6