Looking for boiler control board schematic...

[SteveD CB500K0]

A bit of a long shot this, but...

I have an Ideal Classic LX FF270 central heating boiler which cycles every 10 seconds. I have tried fault-finding all the various sensors but have come to the conclusion that it must be a degraded component on the control pcb.

I can fault-find the pcb if I can find a schematic (circuit diagram) anywhere. I have the Installation Guide which shows pin-outs etc but need to trace the various lock-out logic circuits.

Alternatively, I can get an exchange pcb for about £40 (or a new one for about £140)

Anyone?

Steve

[Woodside]

Has that boiler got the pcb board or does it have the later control box usually grey or orange?

[SteveD CB500K0]

It has the pcb. It is fixed (badly) to the bottom section of the boiler (the one that folds down).

[Woodside]

If your sure it's the pcb for £40 I'd be tempted to get a new one or at least a tried and tested unit..
I do a lot of work for a firm in Reigate who are ideal approved Installers if you want his number I can pm it to you.....
But I'm pretty sure he would just advise a new pcb to...
Not many people these day attempt pcb repairs ...
What exactly are the symptoms....I'm sure you have tested this but do you have atleast 220v on the boiler switch live?

[AshimotoK0]

Is it like the one attached Steve? Ideal are in Hull and yonks ago I took that board and added diagnostics to it  and went in there to try to sell them the design but I got the 'not invented here syndrome'. I did trace out the circuit but my CAD file is long gone. It's only got one chip, which is a 741 style op-amp for the flame ionisation detector. The capacitor for the power supply is only 400v rated not the proper X1 type normally used  for a 'reactive dropper' so I would suspect that and also the DPDT relay contacts onthe two relays. Dry joints is an obvious one too which I am sure you have looked at, particularly around the power resistors. The flame detecor circuit is the only item of domestic gear that I have encountered that must have the L&N correct way round to operate properly. The boards used to be made by IMI Pactrol. Or is it not this PCB Steve?

How about this? http://www.ebay.co.uk/itm/Ideal-PCB-25-/231489398928?pt=LH_DefaultDomain_3&hash=item35e5d7e890

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[SteveD CB500K0]

God you guys are good...   remind me, this is a bike forum right?? 

Yes Ash, it is that board, although mine is caked in dust and grime.

I'll keep an eye out for a replacement.

I have replaced the fan twice in the last 10 years. Looking at the most recent one (£85 vs £150 for OEM), I estimate that there's about £3-worth of cheap motor and £2-worth of tin. Someone makes money on this stuff...

Steve

BTW: it is not an "LX" model, just a normal FF270. A bit of confusion with the labelling (more cheap labour no doubt)

[royhall]

Steve. When you say the boiler cycles, does it run through its entire sequence and actually fire up. If it does fire, does the boiler pipework get very hot then the boiler shuts down. If this is the scenario, the boiler is okay and the pump has packed up. Will need a bit more info to diagnose that problem correctly before you part with your hard earned. Cheers Roy.

[mike the bike]

It look very old tech; a single 741 and relays.  That's a trip down memory lane.

[royhall]

Just a thought!! You are all Gas Safe Registered aren't you. 

[AshimotoK0]

God you guys are good...   remind me, this is a bike forum right?? 
Steve

Yea suppose you right Steve ... but you have the ultimate powers of censorship !! 

 Those cast iron old boilers are great BTW.' Ideal Standard Boilers'  had a problem  that they lasted too long and were easily fixable. They had a patent out on that flame detection circuit using a 741 op-amp! If you need any relays to fix it etc I probably have some if you have the spec. of them or the capacitor. The reactive dropper capacitor is a dodgy component in my view and I told em so at the time ..didn't go down well. At the time I had bought an outdoor PIR lamp for about 12 quid and even the Chinese had the sense to put a proper 'X' rated cappy in their product but Ideal (well Pactrol, as they designed it)  penny-pinched by using a standard el-cheapo one in a safety critical assembly. My mate's  who have a plastic injection moulding  company in Hull, now mould all sorts of plastic replacement parts for them (manifolds, flue parts etc.) ..... will stick with my cast iron one thanks. Roy's correct it may not even be the PCB...if the bug*ers had taken me up on  my diagnostic addition back in '97 you would have had an error code LCD , displaying the cause of  fault !!

"Got a problem with my old boiler mate ...and I don't mean the wife    "

[royhall]

Your dead right Ash. I have been a commercial heating engineer for 25 years, and boiler diagnostics were the best thing ever invented in the heating world. Saved me many a wasted hour.

[SteveD CB500K0]

Symptoms:

1. Boiler starts normally and runs for about 10 seconds.
2. Cuts out and SG1 flashes (and clicks) for about three seconds.
3. Boiler fires and runs for about 10 seconds.
4. Goto 2


It does this constantly, although when it is on all day (ie at weekends) the 10 seconds stretches to two or three minutes at a time.

I have replaced the fan and tested the air pressure switch.

I can fix electrics/electronics, but if it is a gas sensor or valve I will have to get someone in...

Steve

[royhall]

Steve. Is the boiler firing up and getting hot.

If your getting SG1 you need to check the burner electrodes and leads for damage and correct gap, make sure the porcelain part is not cracked and shorting to the case. The gap will be approximately the thickness of a pound coin (doesn't need to be perfect).

If that's all okay, your probably safe to change the PCB. I would have had one of those a while ago unfortunately I don't keep secondhand parts for boilers over 10 years old or you could have had it for free.

EBay is a good bet, there's a guy on there that does exchange units fairly cheap.

Cheers Roy.

[AshimotoK0]

You never reported back on your boiler Steve. How did you get on with it ? Or have you frozen your nuts off 

I just found this in my loft.. it was the prototype I made for Stelrad. It also had a microcontroller daughter board that fitted onto the 8 pin header on the RHS that had an LCD with the diagnostics on it.

Anyway the relays, ignition transformer and spark gap, etc , etc  were all standard Ideal issue and apart from demoing it were never used so could yield parts if you want it (free to you of course).

Ash [ Guests cannot view attachments ]