Hello,

I'm building ICL 7107 digital voltmeter with 200mV full scale as Figure 12 (page 11) on http://www.intersil.com/data/fn/fn3082.pdf
Here is the problem I'm facing:
it shows random numbers, sometimes showing 1666, and it has no effects even when I try to calibrate by adjusting the potentiometer or shorting the inputs pins the values remain the same. Even the whole potentiometer is removed the value still stay there!
I have read through the datasheet and couldn't find any possible defects of the components that might have caused this.
I have tried to replace the 0.1 microfarad capacitor with 1 microfarad but the problem remains the same and I did check the connection trace.
So, I was wondering if you have any idea? and Thanks in advance, that really means a lot to me.

William

 

Make shure that all your common connected together. Do have a circuit you can share?

 

Take a picture of your circuit board or breadboard. May be we can help you spot the problems.

Allen

 

Those chips are easily blown up, I have a meter that uses them. I recall random numbers was the symptom of a blown IC.

 

Hello William,

I think also, that you have a dead IC.

These ICs are very sensitive to static electricity.

Normaly I don't care against static electricity to MOS-ICs, but after killing two of this voltmeter and counter ICs I really take care of proper handling and grounding during installation.

Regards

Rainer


PS: Sorry, if my English is not so good.