Hi all,
I have a company made water level controller which has malfunctioned and wouldn't run the pump when water level goes low.. I guess its a broken logic.. The problem is that all the IC's have been covered by the company with a black substance to avoid local service or copying. I managed to clear 3 of the 4 chips and they were LM324, which I guess is used for the over and under voltage cutoff, a 4066 and CD4093. the 4th chip had its print peeled of with the paint and it is unable to identify.. Its a 14 pin, ST make and of the remaining details it is something like 4X9XN.. First I thought it would be 4093 but all the 4 chips on this device are from 4 different manufacturers.. the overhead tank and water souce level lines Common, Low, High and Dry Run all lead to this chip..Is there anyway to identify it??

 

Hello,

It is not the circuit with the chips you name, but has similar function.
http://forum.allaboutcircuits.com/showthread.php?t=24005

Greetings,
Bertus

 

Ill post the ckt as soon as I trace it out..

 

I tried many times to trace the circuit but I keep on messing over lines. Here's the image of the board and the print side flipped to match.. would this help??

Component Side

Above is the Track Side

These are the connections.

All the sensors are probes immersed in water. Resistive to say.
These are some details corresponding to the component side figure

1,2 - 12v 2A Transformer
3,4 - Buzzer & Warning LED
5 - Ground for LED
6,7 - 9v Double Pole Relay
8 - Motor On LED
9 - Power On LED
Q1 - BC547
Q2 - Something Like 639
Q3 - BC547

 

Is there an ST ewuivalent for that device??