Euronics Automatic Soap Dispenser Repair-1

 

 

 

 

 

Received 3 units of Automatic Soap Dispenser for not working problem., looking at the condition of the units, it seems like someone tried to repair it.

This unit is Battery operated using 4 nos. AA size battery, working on total 6vDC. In this unit Battery department access is in side.

So for inspection I pull down front cover.

First of all, Removed Battery & check each cell, found all are in good working Range.

Now time to take out the PCB & check.

PCB Connectors are Noted before pull out the PCB.

First checked 6v on Power supply wire. Showing 6v

 Then checked leaf switch for working. That is also Ok.

A limit switch is used here for safety. When the front cover is opened, the switch’s leaf is released and the circuit opens. Therefore, the machine will not start automatically while we are filling the soap bottle.

Leaf switch strip working: When the top cover is closed, the leaf switch strip engages and the circuit is activated (Turn ON) & start working on receiving signal from bottom IR sensor.

Here Power section is OK …. now time to inspect the PCB.

On testing Voltages on PCB I did not get any Voltages, checked wire continuity it is showing on top side but not on solder side ………what is wrong.

I found the reason behind not showing any voltage on the PCB while testing.

Reason is “CONFORMAL COATING” on the PCB.

When I flipped PCB solder side under the light, surface is shining.

It is not easy to scratch or remove this coating from solder joints & penetrating the test leads towards solder joint may damage the test probe points.

Here some investment in good tool will pay you back…. Few days back I purchased Micro Grinding Tool mainly used in Mobile repair.

Using this tool, I carefully scratched main solder joints where I take reading.

I checked the voltage at the switch; it reads 6V when the switch is pressed, indicating that the switch is functioning correctly. This voltage line leads to a component marked “V3” on the PCB; its first pin is grounded, the second reads 6V, and the third is at 3.3V. This component appears to be an LDO. The voltage feeds into the controller IC (HT48R05A-1). Since the markings on some parts were unclear, I downloaded the IC’s datasheet and found that pin 12 is VDD and pin 8 is VSS. Reading 3.3V at pin 12 is normal. As I lacked information regarding the microcontroller IC’s reference voltage, I decided to estimate it by tracing the circuit, using a magnifying glass for the task.

I found a faulty component marked R5 on the PCB; its code is 104, which means it is a 100KΩ resistor. Testing revealed that the resistor is open-circuit.

Upon inspection, I found that this resistor was connected to the IR sensor line, and the unit was not working because the IR sensor failed to activate; I replaced it with a resistor taken from a PCB in my scrap pile.

After replacing the faulty resistor, I turned the unit ON and it started working properly.

I cleaned the unit and reassembled everything; now it is time to fix the other unit.

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

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Note: You can check his previous repair articles on XPE COB Light Torch Repaired

 

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