potterton lynx problem

[puzzledplumber]

The fault is now fixed. In fact it was 2 unrelated faults, which is why the combination of them appeared so puzzling. Having changed the sequence and modulating boards without any luck, I also changed the distribution board. This removed the fault whereby the high flame light came on without any combustion. However the fan was still not rotating, and consequently no ignition sequence. Checking the DHW limit thermostat revealed an open circuit at the plug that goes onto the distribution board. However the fault was not the stat, but the crimp between the lead and the terminal in the plug. It seems that it was not crimped very well and when I pulled the plug out of the board when I first started the fault finding exercise, the last bit of continuity broke which gave rise to the open circuit. Repairing the terminal with a soldering iron fixed the problem and DHW and CH are now working perfectly.

To answer a couple of questions that were asked earlier, I wanted the circuit diagrams to try and find why the high flame light was on with no combustion. With the information in the manual it is difficult to trace the fault path, but with a proper circuit diagram it would have been quite easy. And secondly I am located in Essex.

Thanks to all who have replied with constructive suggestions, they have been much appreciated.

PP

 

[Agile]

Thanks for telling us that.

Do you know why the distribution PCB was giving a wrong indication?

The badly crimped connection just shows how useful it is to test components at the point of connection to the pcb rather than at the omponent itself.

Do I take it that you have a local pcb repairer in Essex?

The only ones I was aware of were NW London, Watford and Sutton Coldfield!

Tony

 

[geoff@cetltd]

Adlink have an (independent) outlet over there

If I remember I'll look and see if I can see what's going on with the 407685 tomorrow

 

[Softus]

When I said "again" I meant that again across all the postings which you make you only disect and comment without saying anything relevant to to original topic.

I certainly do that with some topics, but no more often than you do.

Its obvious to everyone else, without me having to say it, that I am giving advice to help my industry colleague fix the boiler and I have no intention of charging for that.

I'm sure you're a nice guy really Agile, but you come across as such a pompous fart sometimes - I don't believe that it's obvious to "everyone", but even if it is, am I not entitled to make a mistake?

If that's what I've done then I apologise for misinterpreting what you wrote and for distracting anyone who's been distracted.

 

[geoff@cetltd]

Adlink have an (independent) outlet over there

If I remember I'll look and see if I can see what's going on with the 407685 tomorrow

OK, I've had a look

The High flame LED connects directly to pins 23/24 of the 407686 between the rail (via a resistor) and Q3 transistor via traking on the 407685. It also connects to the low flame LED on the 407685 via a diode which goes to common.

The only mechanism by which I can see that the high flame on fault would be due to the 407685 is if the diode had gone short circuit , barring sillies like tracking due to water damage etc)

I have never come across this fault in X thousand boards that I've repaired

 

[puzzledplumber]

Raden
I like my faults to be different. Thanks for the info. I will have a look at it in the next day or so, just for interests sake (and possibly having another working board).

Agile
The supplier where I bought it said that they didn't repair them themselves, but sent them off to someone. I had another look at the board to see if there were any clues and have just seen a sticker on it that says.........Adlink with a London phone number, so no new board repairers I'm afraid. I hasten to add that the reconditioned board was in perfect working order.

 

[geoff@cetltd]

Raden
I like my faults to be different. Thanks for the info. I will have a look at it in the next day or so, just for interests sake (and possibly having another working board).
quote]

1N4007

Yeah, they're just a shop selling Adlink recon stuff

crap it is ...

well, I have to say that

 

[Agile]

Totally independently the various information I receive suggests that that firm of reconditioners does not have the facilities to properly test anything other than the simplest pcbs.

The real worry comes over insurance. Pcb turns gas on during the night and the house explodes! Does the reconditioner have any insurance to cover that?

Tony

jakata possible today wed!

 

[geoff@cetltd]

Totally independently the various information I receive suggests that that firm of reconditioners does not have the facilities to properly test anything other than the simplest pcbs.

The real worry comes over insurance. Pcb turns gas on during the night and the house explodes! Does the reconditioner have any insurance to cover that?
quote]

The 407685 really is a simple pcb. I have recently heard quite bad things about Adlink's testing facilities which have been backed up by John (who used towork for them)

I would not let a pcb oput of CET unless I was sure it was propeerly tested and correct components used, as simple as that (with the exception of something straightforward where e.g. a fitter has blown the gas valve resistor on a vaillant pcb)

I have £2,000,000 insurance to cover such eventualities, but if correctly repaired with the right components it's not an issue

 

[Agile]

I heard several years ago about their lack of proper testing facilities.

Worst that they just change a list of common failure components on common boards and if that does not fix them they do not have the expertise to identify anything further so they are abandoned.

Now what about the microprocessor controlled pcbs with SM components? I have encountered several logic faults which only affect operation in specific operational combinations.

On one visit I tested the boiler and could not find any fault. The lady showed me what combination of usage prompted the fault.

A common failure on several different models is on heating that it gets up to temperature on CH but never comes back on again. Perhaps a too long anticycling delay?

Tony

 

[puzzledplumber]

Raden

Have finally got round to looking at the board. I put the faulty board back in and checked the bits you said, but nothing was found wrong. I presume that the diode you were referring to was D12. That checks out ok with the DMM.

The bit of the circuit that you mentioned was at the indicator end and I think that the problem must be at the start of the circuitry as the fault that is giving the high flame light permanently on is inhibiting the normal demand and ignition sequence.

Agile

Interesting comments re the insurance aspect, unfortunately not one that I am really qualified to answer. Also I have no knowledge about how good or bad the aformentioned reconditioning firm is although I would find it difficult to believe that a firm that makes a living from reconditioning electronic equipment would not have suitable test equipment to repair them. Looking at the boards, they do not seem to be that complex and to make a suitable test set would not take too long. Also the board that I got from them worked perfectly.

However regarding reconditioned boards in general, the fact that they have been reconditoned does not necessarily make then less reliable. Electronic circuit reliability generally follows what is often termed a bathtub curve whereby there is a (relatively) high failure rate in the first few hours of operation (the "tap" end of the curve) and then the failure rate tails off and is very low for many hours until the equipment approachs the the far end of the bathtub where the failure rate steadily increases. I would imagine that for the electro-mechanical items on the board e.g. relays, the rules are different, but for the majority of the circuit that will apply. In general there is no reason why a properly repaired board should be any less reliable than a brand new one and may even be better.

 

[geoff@cetltd]

"Raden

Have finally got round to looking at the board. I put the faulty board back in and checked the bits you said, but nothing was found wrong. I presume that the diode you were referring to was D12. That checks out ok with the DMM.

The bit of the circuit that you mentioned was at the indicator end and I think that the problem must be at the start of the circuitry as the fault that is giving the high flame light permanently on is inhibiting the normal demand and ignition sequence. "

Well, I checked the possible paths and that's all there is. Without having the pcbs to test I can't diagnose it any further


"Agile

Interesting comments re the insurance aspect, unfortunately not one that I am really qualified to answer. Also I have no knowledge about how good or bad the aformentioned reconditioning firm is although I would find it difficult to believe that a firm that makes a living from reconditioning electronic equipment would not have suitable test equipment to repair them. Looking at the boards, they do not seem to be that complex and to make a suitable test set would not take too long. Also the board that I got from them worked perfectly.

However regarding reconditioned boards in general, the fact that they have been reconditoned does not necessarily make then less reliable. Electronic circuit reliability generally follows what is often termed a bathtub curve whereby there is a (relatively) high failure rate in the first few hours of operation (the "tap" end of the curve) and then the failure rate tails off and is very low for many hours until the equipment approachs the the far end of the bathtub where the failure rate steadily increases. I would imagine that for the electro-mechanical items on the board e.g. relays, the rules are different, but for the majority of the circuit that will apply. In general there is no reason why a properly repaired board should be any less reliable than a brand new one and may even be better."

well said - at least someone has a clue, just the wrong source of parts

 

[puzzledplumber]

It may be the wrong source of parts, but unfortunately it is the only one I have. If I can find time I will investigate further in the next week or so and report further if I can find anything wrong. Thanks for your interest

 

[geoff@cetltd]

If you can drop them into A10 boiler spares on the cambridge roundabout, I can have a look at them for you

Or where are you ?

 

[puzzledplumber]

I quite often have to go from Essex to Luton (your premises would seem to be just a slight detour-have checked your address using yellow pages and multi-map), so if I have no luck after I next have a look at the board then I may well take you up on your offer. Will let you know. Many thanks.