Potterton Lynx 2 PCB problems

[Strik9]

Hi Guys,

I have a Potterton Lynx 2 boiler that has just developed a problem.

My Ex heard the boiler turn on the other morning and then made a buzzing sound and switched off...... Fuse on PCB blew.

I changed the fuse and set boiler to 24hr operation and noticed the loud buzzing.

When the boiler is in demand for either HW or CH the boiler makes a buzzing sound and does not wish to operate.

I have tracked the buzzing down to a rapidly switching relay (black case, lower relay on PCB). On closer inspection of the relay with black case removed, you can see the switching and arcing of the relay.....

If pressure is applied to the relay arm and forced to make the circuit, the boiler operates as normal...

Does anyone know if this is repairable????


Cheers....

PS... A quick response would be good cos it's freezing in here!!!!!

 

[Agile]

It sounds to me as if the pcb supply circuit is not being adequately smoothed.

If you really are competent with electronics you could try replacing the smoothing capacitor.

Tony

 

[Strik9]

Upon closer inspection of the PCB I can see that there are 2 resistors that have had some overheating issues. I guess C7 would be the smoothing capacitor, as it is sitting right next to the transformer?

I have just found a reconditioned PCB (guaranteed for 1 year) on the net for £35, I may just go for a full replacement, at least then I have some spares... not that I trust them any!

At this price do you think it's worth it?

Cheers.

 

[geoff@cetltd]

That's not me, I charge £40+, so I can't advise

 

[Agile]

"""Upon closer inspection of the PCB I can see that there are 2 resistors that have had some overheating issues. I guess C7 would be the smoothing capacitor, as it is sitting right next to the transformer."""

We cannot afford to make guesses when repairing boilers!

I think that you will find that C7 is the spark generator storage capacitor and the "transformer" beside it is the ignition coil.

You might be better off replacing the large 2200 ­µF 63v capacitor towards the top of the board.

Before you solder it in place you could test my assumption by placing it in parallel with the existing one and see if it cures the fault. Make sure you observe the polarity.

Tony

 

[geoff@cetltd]

"""""""""""""""""Upon closer inspection of the PCB I can see that there are 2 resistors that have had some overheating issues.""""""""""""""""""""""""""

let me guess R1 and R5 ?- the metal oxide ones ... different from the rest because they ... get hot

"""""""" guess C7 would be the smoothing capacitor, as it is sitting right next to the transformer.""" We cannot afford to make guesses when repairing boilers!

I think that you will find that C7 is the spark generator storage capacitor and the "transformer" beside it is the ignition coil. """""""""""""""22

Absolutely correct

"""""""""You might be better off replacing the large 2200 ­µF 63v capacitor towards the top of the board. """"""""""""""""""22

I doubt it - If there was a problem there (smoothing the O/P from the voltage regulator) nothing would be working properly

 

[Agile]

Perhaps not, but can you come up with a better suggestion of what may have failed?

A shorted bridge diode would be even less likely to allow the rest of the circuit to quasi work.

Tony

 

[Strik9]

Well here's a new one for ya...

Replaced the PCB with the reconditioned PCB which looks to be in really good shape... no dry joints what so ever. No tell tale signs of any overheating issues.

Made all the conections, turned on the power with the boiler off, no demand, switched boiler to on.... I can hear the relays click into position. Timer is clicking away...

Call for CH and the 2A fuse blows.... not too sure if I saw a flash near the connections to the gas valve...

What's your opinions on this one?

Cheers

 

[Agile]

I think that you should have called a competent boiler engineer in the beginning to properly diagnose the fault.

Did you ever measure the resistance of the pump and gas valve coils?

Tony

 

[Strik9]

I think that you should have called a competent boiler engineer in the beginning to properly diagnose the fault.

Did you ever measure the resistance of the pump and gas valve coils?

Tony

Well you're probably right.... I should have called a competent engineer.

Anyhow... What sort of figures are we looking at for a correctly functioning coil?

Ok.... let's see if we can get to the root of this problem...

I have checked the Gas Valve and it is not that which causes the fuse to blow.

I have checked the Fan and it is not that which causes the fuse to blow.

I have checked that the pump is running freely and it is.

I have connected every connector apart from PL1 whose colours are:

>Black
>Black
>Black
>
>White

All appears to function until this connector is affixed to the PCB. When there is a demand for Hot Water or Central Heating the fuse blows.


TIA.

 

[Strik9]

Opened up the electrical box on the side of the pump and noticed that it was quite moist in there???

It smells really bad too, quite like cat or mouse pee!!!! Gonna test it on a live spur to see if it blows a fuse!

 

[geoff@cetltd]

Well here's a new one for ya...

Replaced the PCB with the reconditioned PCB which looks to be in really good shape... no dry joints what so ever. No tell tale signs of any overheating issues.

If it was from CET, you can phone up for support

 

[Strik9]

Gonna test it on a live spur to see if it blows a fuse!

Fuse blew whilst testing on a spur...
Pump Goosed!!!
PCB Goosed
Water Pressure switch goosed too....

Gonna have a new boiler before long!

 

[Agile]

You should have had a new boiler a long time ago!

 

[Strik9]

You should have had a new boiler a long time ago!

Yep a very true statement indeed... I'll leave that up to my EX and she can decide if she wants to spend in excess of £700 just before Xmas to have a new boiler fitted!!!

Up until now it's cost about £144 for all the parts. Fingers crossed, it'll take her up to the warmer months and she can get a new one then.

Thanks for your help and patience... We'll see how the new gear fairs. I'll probably be back on here posting by the end of the day with more tales of woe!

Merry Christmas All