Thermostat

Wirsbo Thermostat

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My friend has 5-6 Wisrbo 80465 thermostat broken.

I looked one.

It has all kind of electronics inside.

I started to draw a schematic diagram.

It was like this.

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I put +24VDC to pin 2
I put to pin 3 LED + 470R resitor to show when load is on and other end to pin 4.
I put ground to pin 4.

When I measured it , I found that double SMD-diode D3 was broken.

I replaced diode, which was marked A7W with similar BAS70 diode.

It started to work.

Wirsbo.jpgWirsbo1.jpg

My friend give me a three broken thermostats more.

All have broken diode D3, BAS70.
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At July 2018 I got three other thermostat, same make, which were also broken.

One has all the diodes broken and R13 open, and IC1 broken. Maybe it has got 230V power?

Other has D3 and D1 open. D4 was shorted.

The last has IC1 open power circuit at pin 4, the PCB circuit was some how open, also D4 was little, but only little short circuit.
It eats power.

I changed to all diodes to better quality type.

Pekka OH3GDO

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