Intermittent Potterton? Flashing red LED? PCB Fault finding

[geoff@cetltd]

please dont tell subject author about puma pcb's that go on fire.

Never had that, but have had a fan sieze on an ideal elan which kept trying to spin it, melted the relay and set the board alight.

Common problem on the Stel 7A/B board

As for Pumas, I hve hundreds of pcbs where a wedge 2" by 1/2 " has completely burned away

 

[Agile]

So Chris would say you add a wedge 2" x ½" of car body filler?

What do you do when a 2p 3w switch by Palazzo from Torino burns up?

Tony

 

[Gasguru]

Anyone worked on Grundig TV's from the 70's ? Circuit boards had more burn holes than a swiss cheese.

 

[geoff@cetltd]

"So Chris would say you add a wedge 2" x ½" of car body filler? "

Yes, I have serious doubts about CR ... 10 minutes to recondition a fan indeed !

"What do you do when a 2p 3w switch by Palazzo from Torino burns up? "

Swear profusely in Italian ...

 

[rikkitikki]

This is an old thread but here is my 2 cents anyhow. There are enough of these potterton suprima bangers, er I mean boilers, on their last legs. Just want to give hope to anyone facing a hefty pcb repair bill

My boiler had been doing the random lock-out routine. I mean random as in go on holiday for two weeks leaving the heating timer off. Come home to boiler in lock-out mode and pump running non-stop wasting electricity.

Soooo, following the advice on this thread:

removed pcb
checked for dry joints with magnifying glass
and found at least 10 suspect dry joints

It must be emphasized that without a magnifying glass it is really difficult to spot dry joints. The solder fractures are barely visible even then.

Re-worked all the solder joints on the PCB plug connectors anyway.
Then re-worked all the suspect component joints.
Just to be sure I then re-worked some joints that seemed to have insufficient solder.

So the big question...How are intermittent faults tested after a repair attempt?

If 4 weeks go by without a lock-out I will be fairly optimistic.

Watch this space.....

 

[daverogers123]

I find many of these problems are caused by the control board, microscopic cracks in the solder joints causing connection issues particularly where the board connectors are soldered on, and especially where high currents are switched (like the output power to the pump, which if it doesn't get power will cause an overheat condition)

And PCB subjected to temperature cycling is prone to joint cracking, particularly now after lead was banned from solder in 2007. making joints more brittle.

I've found that 9 out 10 boards faults can be repaired by re-soldering the joints.

Dave Rogers