I have a fault in the spark generator circuit on a Potterton 407677 pcb and traced it to component SP1. Trouble is there are no identification marks on the component so can any readers identify this part ?

Chris, April 2016

My spare 407677 in front of me has a TF1 (transformer 1) the designation SP1 presumably stands for Spark 1 because there's only one of them on the circuit board.

My TF1 is marked E 3746/3 on the case - I have seen one on e-bay for just £2 they are commercially available (I think) - search on the 3746/3 number.

I think the letter E stands for EICHHOFF the manufacturer
http://tinyurl.com/goy54ud

Also known as T003-746/003

Good Luck..., April 2016

How do you know "SP1" is faulty if you don't know what it is?

Based on a quick Google Images search, "SP1" looks like a spark gap which will, until 100V or so (depending on spec) are applied, will show completely open circuit. Think Neon lamp.

WHat usually happens is there is a small reservoir capoacitor that is charged via a resistor from a couple of hundred volts (Rectified mains, possibly). Across the capacitor there will be a spark gap in series with the primary of the ignition transformer.

When the voltage across the capacitor reaches the striking voltage of the spark gap, the contents of the capacitor are dumped rapidly thru the primary of the ignition transformer until the voltage on the capacitor falls below the extinguishing voltage of the spark gap. The cycle repeats as long as power is applied.

I very much doubt SP1 is at fault, but you are welcome to check

this may help a bit:

http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler

http://kaijaks.co.uk/blog/nick/2009/03/01/boiler-pcb-407676

http://kaijaks.co.uk/blog/nick?disp=comments

http://www.euroboilerparts.co.uk/pc332-compatible-potterton-brprofile-prima-407677-40767701-1099-p.asp

All those were from a couple of minutes on Google

Anon, April 2016