Protek 506 Voltage Measurement Problem

[mustafayilmaz]

Hello,

I don't use Protek 506 very often. There was no overload situation on the device.

When I wanted to take a measurement the other day, I realized that the measurement was incorrect. I corrected the commutator and tried again. It did not measure AC voltage. It appeared as 0.000V.

I disassembled the device and cleaned the comitator legs. It gave accurate measurements for a short while. Afterwards, I see extremely volatile values. The voltage, which should normally be 10.5, appears to vary around 11~13 over time. I think it changes slightly when the device shakes.

It shows values around 40~45 C in the temp level.

At the mV level, when the probes are short-circuited, it is 0mV. When the probes are open-circuited, the voltage increases within a few seconds and appears as OL.

It makes incorrect measurements at Temp, ACV, DCV and mV levels.

In addition, the diode stage is working properly, but when the probes are idle, they are close to the required values, but the voltage value on the screen is not stable.

I did not see any defective material. But ZD15 shows 0.5~0.6V diode voltage in both directions.

[mustafayilmaz]

The measuring device now makes accurate measurements. I think there was a lack of contact somewhere.

The problem at this mV level still persists. Will it be fixed if I change the reference voltage?

When the probes are idle, a voltage of around 300-400 mV occurs. It's like a capacitor charging and eventually the screen says OL.