CET Ltd : Suprima 80 boiler

[boxst]

Hello

I am having problems with my boiler and assumed that it was the PCB. A quick call to http://www.cetltd.com/ and the next day a refurbished circuit board turned up.

It doesn't solve my problem, but just I thought I would report on superb service.

Steve

 

[Agile]

You were hoping to save money by not using a professional to diagnose the problem and then using a repaired PCB.

Now you dont know if the repaired PCB is also faulty or if there is another fault!

Whilst DIYers can use repaired PCBs although if there was an explosion your home insurance might not cover you, professionals are not meant to use parts not approved by the manufacturers.

The PCB controls the operation of the gas valve and turning it on when it should be off could be very dangerous!

Tony

 

[ollski]

can't see how using a board refurbished to the original spec can be argued with, after all it is simply refurbished not modified. Although why you would bother using a refurbished board with a design fault seems a false economy.

If anyone is interested I have 20 used suprima boards in my shed waiting for refurbishment, just make me an offer.

 

[Agile]

If Potty were happy with them then they would approve them! In any case why do you really think they are "refurbished to the original spec".

As far as I am aware there is no single design fault. After all they work for a while dont they. They just seem highly unreliable and rarely last three years at the most. We took out a 2003 one yesterday.

I would offer £20 for your old boards! ( Thats for the lot not each! ) Just to play with not to refurbish! It frightens me when we fit replacements as we are expected to give a reasonable guarantee on our work. I reacted badly when one failed after seven months, I explained our dilemma and we fitted another for the cost of the part.

Tony

 

[ollski]

If Potty were happy with them then they would approve them! In any case why do you really think they are "refurbished to the original spec".

Tony

Hmmm hang on tony, can imagine that dilemma at baxip, "shall we approve these boards so folks can buy them from someone else at 50.00 or shall we keep insisting they are bought from us at 200.00 a piece.....hmmmmm"

I presume they are refurbished to original spec so as there are no legal implications, but I don't know for sure, and as for the design fault the sheer numbers of replacements and scorched boards would seem to point that way as it is not aproblem across the whole business.

 

[gazthepottertonengineer]

can't see how using a board refurbished to the original spec can be argued with, after all it is simply refurbished not modified. Although why you would bother using a refurbished board with a design fault seems a false economy.

If anyone is interested I have 20 used suprima boards in my shed waiting for refurbishment, just make me an offer.

Yes but the fact is they dont use he same components so how can it be to the same spec ????

And the fact still stands that the suprima did nothing for pottertons quality reputation like the Netaheat,Profile,Kingfisher etc took so long to create ?

 

[ChrisR]

I presume they are refurbished to original spec

but there IS NO SPEC AVAILABLE! It isn't just a question of eyeballing a board and putting in a new component. You would be assuming it will do the same job in that specific application, but you don't know what the job is. Some of the components on a Suprima board are potty-designed.

Potty claim that some of the compnents are no longer available which is why they redesigned the board. You never know, it might be true!

Also if safety section A blew and took component B with it, the board might "work" if B were replaced, but the safety section would be missing.

"Refurbished" means different things too. Puma boards often blow the solder in the corner, but the relay contacts are usually pretty black by then too, so who pays if they stick inside 3 months?

 

[ollski]

can't see how using a board refurbished to the original spec can be argued with, after all it is simply refurbished not modified. Although why you would bother using a refurbished board with a design fault seems a false economy.

If anyone is interested I have 20 used suprima boards in my shed waiting for refurbishment, just make me an offer.

Yes but the fact is they dont use he same components so how can it be to the same spec ????

I would imagine if the electronic component manufacturer be it philips, marconi or who ever advised one component was a direct replacement for another that is ok. Obviously not all boards are suitable for refurbishment but most are and to be honest with the history on this boiler I would prefer to shell out 50 notes for an old board which might be ok than 200 or more for a brand new board which might be ok.

 

[ChrisR]

COmponent manufacturers absolutely categorically do not advise that one of their products would replace someone else's! They make suggestions but it needs an electronic design engineer, who understands the operation of the circuit, to make the judgement.

You might have two resistors, same value, same power rating. But their temp coeffs and tolerances might be different, and more importantly their failure mode - whether they go high or low resistance, open or short completely. That's just a few parameters - the number for an active device like an op amp, comparator or transistor is far higher. A parameter which makes a component particularly suitable in one application may make it useless in another. The decision on a replacement would not typically be taken by anyone without an electronics degree.

It's always tempting to think someone else's job is simple!

 

[Agile]

I know somebody with connections with one of the other PCB repairers. Its pretty frightening what he told me.

The have a list of components for each pcb model which they change on every returned pcb. They test it on a simulated boiler, if it seems to work they sell if it doesn't they bin it as they dont have the expertise to fault find.

They have no specifications, even the boiler manufacturers often dont as many buy in ready designed PCBs.

As Chris says they have no ability to know if the repaired PCB performs all its functions or if some leser functions like on board frost protection are working.

Most dangerous of all the purchasor does not know how the board will respond in the case of a fault on another component. Many PCBs use components selected to fail open circuit if the current taken for example by the gas valve is excessive. These can be special fusible resistors or just a particular make which is known to fail o/c ! Replacing those resistors with any old resistor could cause it to catch fire!

Tony Glazier

 

[ollski]

points taken, my c&g in electronic engineering is a very distant 20 years ago and I don't proffess to have any knowledge or interest in it, but lets take away the theoretical problem that like for like parts are unavailable and work on the assumption that they only fix boards where the exact same component is available and general resoldering etc, is there still a problem here because I don't see it.

 

[ChrisR]

Sure! You often can't tell the make and model of a component by looking at it. Some don't even have generic type numbers on, so all you might know is that something is "a pnp transistor", "a capacitor" etc.
Another of course, though it doesn't apply to a Suprima pcb I expect, is that some things are adjusted on testing the board after manufacture to deal with differences between components.

I wonder how many people would recognise the Fusible Resistors on Suprima boards. I hadn't a clue about them until TG pointed them out.
Tricky to spot the zener diodes too.

DOes depend on complexity too - there aren't many mysteries on a Profile board!

 

[Paul Barker]

It would be very bad design practice to build in failure modes on the pcb to protect against failure of an extrenal part, because when we bought a new pcb it would also fail.

I can see no harm in getting a pcb working with better quality parts. If it interfaces with the boiler all is well.

Not that I'm saying a refurbished board is better, or isn't worse, but it's horses for courses.

Take a recent example Ideal Classic with electronic ignition fanned flue. Boiler not lighting, on examionation fan not coming on, a look at the pcb fan relay smokey colour on glass, tap fan relay with but of screwdriver boiler fires up. If I had the relay in my parts bits I would have changed it. Sent it to cet, new one was £35, probably not worth me searching the rs catalogue and firing up the souldering iron.

Clearly on this boiler the fan relay is a much used and soon worn part.

Question? Why not use a plug in relay with a standard relay base which we can change by plugging in?

 

[ChrisR]

"It would be very bad design practice to build in failure modes on the pcb to protect against failure of an external part, because when we bought a new pcb it would also fail.
"
Sure, but that isn't quite what I meant, if it's aimed at me. Some parts are certainly designed to fail safe. If you use a tantalum bead capacitor it will usually fail short, where a foil one will fail open. You wouldn't use a tant if it would mean taking out components on another board when it went.

Problem with relay base could be that someone would plug in one with the same connections, but inferior in some way, perhaps even if superior in others.

You can't always say component A is better in all respects than component B.
As I said, a lot of them will have a long list of relevant parameters, which is why it takes a true engineer to make the choice. He has to consider all the factors which he can work out from the circuit design, are relevant .

Something close would happen in plumbing when deciding what pump should replace some obsolete one. We could all write down 6 or 8 parameters which may or may not be important, with maybe a couple we'd have to find out about.
Peak head, peak flow, head/flow at different points in between, noise, duty, starting characteristic, power factor correction required, materials of construction, temperature rating, connector type, service interval, power requirements, self priming, priming plugs fitted, size, cost, availability and on and on. Then you might find an identical pump, just a bit higher head, so it must be better, right?? ?? Well it depends....!

Only a plumber with an idea of electrics (which may not be enough) can make an informed judgement about a replacement pump.

"If it interfaces with the boiler all is well. " But if you don't know everything about it, you can't judge.

A pump's a bit like an amplifier, but it's a damn site easier to choose a replacement pump.

 

[chrishutt]

But if you don't know everything about it, you can't judge.

But that leads us once again to "unknown unknowns". Nobody knows everything about anything. They might think they do, but since you cannot know what you don't know, you cannot conclude that you know everything.

The upshot of which is that all "judgements" must be made without knowing everything, in some degree of ignorance. The electronics engineer makes his best judgement about the specification, etc. of PCBs, but as we all know too well, mistakes are still made.