The dreaded 'buzzing' problem

Ok I have researched this forum and established that I have this quite common fault. Resolution seems to be replacement of the two pump pcbs and some kind soul on here gave details of an internet company who supply them. Before I spend the best end of £150 can I ask - is this a job for a non-techie? I have previously changed the pcb in my Potterton Suprima Boiler (with the aid of a simpleton guide) and it has worked perfectly since. Are any special tools required? Is there a basic guide for the non-professional or can someone who has done this job offer step by step advice? Finally whilst the buzzing is horrible, the system appears to be working fine - is any long term or more serious harm being done by leaving it alone? (apart of course from the danger to my own health from my wife getting on at me night and day to get it sorted! haha) Any help would be very much appreciated.

really simple wire for wire change over if you replaced the potterton board this is a breeze, see if you can confirm which board is faulty before buying both as its very rare they would both go, get the unit buzzing each board carries a relay the largest part on each board usually says omron on it gently push each relay with a biro end or lolly stick to hear a sound difference this will confirm which board is faulty, just be careful and dont touch anything else !! when removing either old board beware of the pegs that hold the board in place as they do become brittle and have a tendancy to snap off.
good luck with that.
regards
mark
THERMAL SOLUTIONS
www.gledhill-repair.co.uk

Mark, thanks for that, Des

What are the name of the pcb's and where can i perchase them from please? anyone?

I picked up from this forum the following information but have yet to purchase so can't yet confirm availability from the stated company.
website ; keeptheheaton.com (under menu for Gledhill Spares)
Pump Drive PCB ; XB104 (order No 114447) £59.61
Pump Delay Timer PCB ; XB041 (order No 107383 £59.95
Add VAT to these prices and approx £6 for post & packing.

Good Luck
Des

Ok, plucked up a bit of courage and took off the cover on the Boilermate 2. Identified that the board that is buzzing is the uppermost of the two. I'm gonna kick off by replacing this one and see how it goes. However, I don't know which one this is called - Pump Drive PCB or Pump Delay Timer PCB? Can anybody help me with this please. Thanks Des

Ah found a picture on EBay so its the Pump Drive PCB.

http://shop.ebay.co.uk/i.html?_nkw=pump+drive+pcb+for+boilermate+&_sacat=0&_trksid=p3286.m270.l1313&_odkw=pump+drive+pcb+for+boilermate+2&_osacat=0

This seems to be a new item at nearly half the price that others are selling. Anybody got any views about its suitability? Thanks Des

will be fine.
mark.
www.gledhill-repair.co.uk

Cheers Mark. Part purchased off EBay. I'll post again when job is done to advise how it went (for anybody else out there of non-techie ability with similar issues) Des

New PCB arrived and fitted in 5 minutes! Bliss - no more buzzing and everything seems to be working as should. Very simple fitting procedure:
Power off at consumer board
Undo 4 screws and pull off white Thermo knob plus its washer behind
Take off front cover, leave attached to earth wire and carefully stand it aside
Disconnect 4 wires from numbered block having first coded with tags/pen. (Note one wire is just a loop from
terminal 2 to 3)
Carefully prise old PCB off plastic securing pegs - gentle squeeze with small pliers whilst pulling board forward seemed to do the trick.
Refitting new PCB is simply the reverse procedure
I'm no techie and this was very easy even for me.

told ya
mark.
www.gledhill-repair.co.uk

Mark, top man. Many thanks for the help and advice. Regards Des

Jut a note on the real cause of the problem here. The circuit boards use a cheap and relatively crude (but effective) power supply to convert the 240v AC mains to 12V DC or so for the relay control. Critical to this power supply are smoothing capacitors, which contain a liquid electrolyte (hence electrolytic capacitors). Now the supplied capacitors are only rated to operate at up to around 40 degrees. Using them on a circuit board attached to a tank of water at 60 degrees significantly shortens their life. When they dry up and stop storing charge, they are no longer able to smooth the 50Hz from the mains - the buzzing is the effect of switching the relay on and off 50 times a second when the pump fires.
So by all means replace the whole board, but expect it to fail again within a similar timeframe. Alternatively find someone who knows how to wield a soldering iron and get them to replace all the electrolytics on both boards with high temperature ones from Maplin. I did mine for a couple of quid.

Jakd - I've bought a new board to tide me over for the moment - I'm having this problem with the delay timer.

The only problem I've had is isolating which caps to replace.
C3 I presume should be replaced.
C1 I presume should be replaced.
the question I have is should D1 and D2 replaced, and are there any I've missed?

and what value capacitors/diodes should be used. Casing values aren't all too clear on the caps.

I replaced the relay, thinking it might have been that causing the problem, but now stumbled across this forum which tells me otherwise.
Thanks in advance,
Anthony

OK, so I've been doing some work on the board this morning.

Replaced both capacitors. Have not tested the board yet as at work.

Jakd - perhaps your board is different to mine. All my capacitors are rated to work to 85 degrees.
Interestingly, I did an in-situe test on the diodes (D1 and D2). It is very possible, being that they directly connect with the relay, that they are causing the problem. The reading is infinite in one direction and '0' in the other. It may be that they are short circuited or I'm picking up a false reading as they are connected to the relay and I'm reading the value off the coil.

So...

I will test the Diodes today off the board and revert, but for reference the values of the Capacitors are as follows:

C1 = 63v / 22uF
C3 = 16v / 22uF

Technically, you can replace the capacitor with a cap of higher uF value, but the same voltage.

If they're now using caps rated to 85 degrees than that's good, but I suspect they'll still dry out eventually. How old is it? If you're getting the buzzing then I am pretty sure it's the capacitors. I doubt the zenner diodes have gone short circuit - this would put high voltages on to the board which would fry it. You can use a slightly higher value capacitor, but don't go too high or it will draw too much current and that will fry the diodes