Boiler PCB Repairs

[GB]

We have an old Geminox boiler. Spare PCBs are not available. Is there anyone who can refurbish these boards?

Otherwise, we need a new boiler, which won't happen for nearly a month.

[Andy Burns]

I assume you've asked Geoff?

[T i m]

A big thumbs up for Geoff. I took a boiler PCB over to him a few years back and he sorted it quickly and efficiently. ;-)

Cheers, T i m

[GB]

Thanks, Andy and Tim. Geoff seems like just who I need. Even better, I'm in N London, and Watford is only a half hour drive.

I've got a guy coming in the morning to diagnose the fault on the boiler, and I'm 99% sure that he'll say it needs a new (unobtainable) PCB. If Geoff can fettle the old one instead, that'll do nicely.

[Andy Burns]

Dunno if he can fix brands that he doesn't mention though, is Gem related to Geminox? Best to give him a phone call ...

[T i m]

The only reasons he might not be able to that I can think of is if it contains components that he can't get or doesn't have a test jig to suit etc?

That said, he's also pretty sharp at spotting (and fixing) dry joints, not an uncommon cause of issues on these things as I understand.

I agree with the call before moving though (and I think he only works with appointments)?

Cheers, T i m

[ARW]

Ask him for a guided tour of his factory if you are into that sort of thing. It's not big but it is interesting.

Also ask him if he has ever set fire to his jumper:-)

we were both pissed up that night.

[Brian Reay]

If you haven't done so already and know how to, it is probably worth checking for dry joints and touching up any that look doubtful etc. Older PCBs in all kinds of things in the domestic (and other) area(s) can be 'magnets' for dry joint pox ;-)

Likewise, a visual check for cracks in the PCB and/or tracks- you can bridge cracks in copper track with wire and solder.

[GB]

It managed to blow a 3 amp fuse in the mains supply. I've replaced that, and I've checked that power is reaching the mains switch on the front PCB. I've stopped there, and I'll let the expert have a look tomorrow.

I'm hoping he'll isolate which of the PCBs is at fault. I assume there's a PSU in there somewhere, but it's not particularly obvious where. It's a 1998 boiler, so would duff capacitors be a possible issue?

[ARW]

He is not the CEO of a multi national company with a waiting list to see him!

It's Geoff.

[Dave W]

When I was doing domestic TV development, a frequent problem (mainly in other manufacturers) was metal components which held a lot of heat, and took longer for the solder to set. If they were moved too soon in the solder bath, probably with vibration, a crack would form all round the solder blob. The PCB worked fine initially but the crack comes apart after some time.

This happenef to me recently on a power transistor with thick leads. I must have knocked it untintentionally rendering the radio mysteriously dead. Eventually I found the transistor just flopping about in the PCB.

[alan_m]

And if re-soldering DON'T use lead free - use 60/40 tin/lead with an integral flux. The flux will have been washed from the PCB during manufacture so if applying a soldering iron you need more flux, either from new solder or from something such as a flux pen.

[Brian Gaff (Sofa 2)]

Don't let the bloke coming round sabotage it though so he can flog you a new boiler. Brian

[GB]

I went over this morning and met Geoff. He gives the really strong impression he knows exactly what he's doing.

I mentioned Adam's name, and he didn't throw me out. :)

[Brian Reay]

Fair enough, I just thought I'd mention it.

As for the capacitors etc, could be but there are other things- including secondary damage if a cap has gone bad.

Unless stressed etc, semiconductors are generally long lived, ditto most other things. Caps are the exception. Plus, manufacturers tend to penny pinch and use cheap capacitors.

The 'PSU' may be a simple as a Cap in series with a diode and another C and a resistor, perhaps a zener. A lot of domestic items forego a transformer or switch mode based PSU and just have a simple 'dropper', rectifier and some smoothing. They may throw in regulator like a 78XY series if they are in a generous mood.

[Dave Plowman (News)]

That's just because it's almost Xmas. ;-)

[The Natural Philosopher]

Ther problem is electrolytics . To get decent capacity these are wet electrlyte aluminium oxide layer polarised shit. They dry out and develop high onteral resiatance and lose capacitance.

Semiconductors DO age. The doping drifts. This happens faster at high temps so power devidces like diodes and switched mode stuff has a finite life - probably no more than 30 years MTBF.

[ARW]

He is a very smart bloke, brain wise not dress sense!

So can he fix it?

[GB]

He says yes. Waiting for some components that he should get in on Thursday.

[Dave Plowman (News)]

And I thought you once worked in electronics.

Plenty early solid state electronic devices still working at well over 50 years old. If they were well designed in the first place.