Potterton Suprima 50L

[Jeff Layman]

Gone into lockout. Almost certainly the PCB, but according to the picture here (middle of page - right hand) we already have an upgraded replacement board. But I don't know how long it's been in the boiler.

Anyone replaced a PCB on a 50L, and had issues with the new board? I see they are available from several sources for £200 - 250 (cheaper on ebay, I know), and I haven't yet checked to see what Baxi would cost to come and fit it, and deal with any other faults which may have caused problems for the PCB.

[ARW]

You need

And Geoff that owns it will give you advice as to possible causes of failure.

[Tim Lamb]

Also, go over the circuit board looking for dry joints. Particularly where the supply is connected. Best with a magnifying glass.

>

[Jeff Layman]

Thanks for the tip, although I see that they sell reconditioned PCBs. Those on offer for the Suprima 50L are AFAICT, old-type boards which have been superseded by a newer design (5111603 - see ).

[Jeff Layman]

Good tip. I'm thinking about doing that in the next couple of days. Can't see that I've got anything to lose by it. We were thinking of getting a new kitchen in a couple of years, and a new boiler might be a bit of a tight fit in the current cupboard. If we can keep the Suprima going in the interim, that might solve a small problem.

[Andrew Gabriel]

There's a diagnostic sequence to go through to narrow down a fault. You haven't given anywhere near enough detail if you were looking for suggestions. In particular, at what point in the startup sequence (or running) does it lockout? There are plenty of things other than the PCB which can fail.

[Jeff Layman]

Lockout is at stage 1. The power is on, the green light flashes, clicking occurs, but no flame or pump activity. Eventually the green turns to red after several tries at lighting. Then it tries again after a few seconds, and continues that cycle. Sometimes it actually stops with the red light on and stays in that condition. Interestingly, the service manual I have (as paper and downloaded) refers to a previous layout where there were two separate leds to show the operating condition. Our boiler has only one where the colour of the led changes with the operating state (see photos in my OP link). I have the customer instructions for that one-led system, but not the fault diagnosis. It is possible to work between the two but it doesn't make life easy!

Our boiler service guy came yesterday, tried testing a few things (pressure switch in particular) and said that with the known problems with the Suprima PCB, it was more than likely to be that. Interestingly he said it would be cheaper to call out Baxi-Potterton to effect a repair, as they had a fixed-price service deal which covered, he thought, up to four faults. I haven't called them yet to see what they charge (our service guy thought it was £300!...), as I thought it worthwhile asking here for any ideas first.

[Jeff Layman]

(see my OP for background)

I decided to follow the detailed fault-finding process in the manual, and if that didn't help have a look at the PCB. In fact, I had a look at the PCB a lot earlier than I intended due to the idiotic design of the Suprima.

One of the first things the manual suggested was to check the fuse on the PCB. When I discovered where it was, I found it was not accessible without dismantling the electronics section of the boiler! See here:

It took a while to work out how to get the box containing the PCB out of the metal case around part of it. Suffice it to say that I haven't found a box held on by a potentiometer nut alone for a very long time. Once out, I could get to the fuse. A simple black plastic holder, so press gently and turn to release...and the case cracked in half (pretty neatly, I should add). A short search for some star bits to get the PCB box cover off, and out it came. First thing was to get the fuse holder back together with some epoxy. It should have been straightforward, but the holder was distorted. Anyway, now repaired it held the fuse properly. The fuse tested ok.

The PCB is complicated and full of surface mount devices and is at least double sided. I had a quick look with a loupe but all the components and wiring seemed ok. There were no obvious cracks or discolouration. Many of the solder joints were shiny, while others were dull, but nothing appeared to be loose. In any case, my soldering skills do not extend to SMDs. For those interested, photos of both sides of the PCB are here:

I reassembled everything, and turned the boiler on to find it still not working. Although not locked out (led not red), the led just flashed green and a relay clicked. A flashing green led is supposed to indicate "boiler temperature control satisfied". Worst of all, the damn programmer display had disappeared even though I didn't need to touch it or its connections! It is still possible to see it operating as the water heating and CH leds work on it, but no time shows.

So I think I'll have to call for professional help before I do any more damage...

[Vir Campestris]

Like CET, mentioned up-thread. I've used them, and been happy.

Andy