Hi all,

Thanks for reading.

I have a VERY old Gas fire which works/worked fine.

The PCB for the on switch suddenly stopped working.

The resistor (pictured R1), I think, has packed in because if I bridge the gap between the 2 points, then it stays permanently on. (bypasses the switch)

I cannot get a new part for this relic, so I will try to change the resistor.

Can anyone please advise what resistor I need? I have no idea.

Thanks in advance.

 

I would say 1210 ohms 1% , (1.21K)
If you have multimeter, test it on Ohms.

 

The resistor (pictured R1), I think, has packed in because if I bridge the gap between the 2 points, then it stays permanently on. (bypasses the switch)

That is not necessarily true.

Most likely, it is the button that has failed. With the board not powered, measure the resistance across the switch, pressed and not pressed.

 

resistor looks ok and in low power circuit like this, it is extremely unlikely for it to fail but - multimeter can confirm that.
i also agree with BobTPH that it is much more likely that button has failed.

 

Thanks, I'm not massively technical, but I do have a multi meter.

I have done what you say and without the switch pressed, it reads 0.

Then pressed, it spikes.

I did the same with the resistor, and it seems to hold a steady number.

(assuming I set the multi meter up correctly.

I also plugged it back in live to re-test. When using my thumb to bridge the resistor, it turns on. Then press the "on" button it turned off the fire.

Removing my thumb from the resistor broke the circuit again so there was no power at all.

Thanks

 

Test it on Ohms , post a picture of your multimeter so we can tell you what setting to use.

 

Test it on Ohms , post a picture of your multimeter so we can tell you what setting to use.

Great thanks.

This is what I had it set on.

 

ok measure the resistor on that range and it should say 1200 ohms or1.2K, try it on the 20K range as well.

 

ok measure the resistor on that range and it should say 1200 ohms or1.2K, try it on the 20K range as well.

Awesome thanks.
It read a solid 1.200

What would suggest the resister is faulty? Or the Switch as BobTPH suggests

 

resistor looks ok and in low power circuit like this, it is extremely unlikely for it to fail but - multimeter can confirm that.
i also agree with BobTPH that it is much more likely that button has failed.

How do I test the button with the multi meter?

It spikes upon initial contact then settles at 0 button pressed or not

 

same way, when you press the button it will read zero,and open circuit 1(OL) when left alone.

OR you can use the Diode function and when you press the switch it will beep and show zero,

 

same way, when you press the button it will read zero,and open circuit 1(OL) when left alone.

OR you can use the Diode function and when you press the switch it will beep and show zero,

Ok thanks,
I tested the Switch the same way.

Reads 1 without being pressed.

I press the button and it then decreases to 0.00

Does this suggest both the resistor and Switch are OK?

 

Yes switch is good, did you measure the resistor on the 2K range and it reads 1200?

 

Yes switch is good, did you measure the resistor on the 2K range and it reads 1200?

Correct I did this too.

2k range read 1200

 

The fault appears to be somewhere else.
Is the photo showing the full size of the board?
What other components or boards are there to see?

 

The fault appears to be somewhere else.
Is the photo showing the full size of the board?
What other components or boards are there to see?

That's the whole board with 4 wires connecting to it from the plug.

I've tested again and it only works when I put my thump over the resistor.

Let me try to video it

 

Video link below.

 

The resistor is just a series limit for the led, there must be another problem with it?

 

The resistor is just a series limit for the led, there must be another problem with it?

It's beyond my capable mind lol.

The only way to get the fire to work is by doing the thumb trick.

Is there a more permanent solution rather than my thumb?

 

post good photos of the PCB front and back so we can check how they are connected. also check if there is a break in PCB tracks if the PCB was bent (button pressed too hard). that would explain your workaround where you are pressing on the bottom side of the board (tracks side). this bends the board back and broken tracks make the contact. the same would happen if resistor is not soldered correctly (cold joint). this is fixed by touching up all pads with soldering iron. broken tracks can be cured by adding wire in parallel (connecting pads that are on same track).