http://www.zen22142.zen.co.uk/Prac/repair_cap.htm

 

"As a capacitor ages, its electrolytic series resistance (ESR) increases. If the capacitor forms part of a power supply then higher ESR results in worse smoothing and the ripple voltage increases. Higher levels of ripple will be heard as "Hum" at line frequency. Line frequency is 50Hz for UK and Europe and 60Hz in North America."

 

I suspect that the advice contained in the last paragraph of this article probably applies to the dysfunction in my kit, as well as a lot of others.

 

I take it that the manufacturers are limiting the life-time of domestic consumer electricals by the simple act of installing short-lifed capacitors i.e. same as it was 10-12 years ago with motherboards.

 

And, I further presume that if delivered power output becomes increasing unstable with age, then presumably, as an added bonus,  all the other components down-line, i.e. in my case the magnetron and quartz bulb are damaged before the power supply unit does its party piece and expires.

 

 

Nick

 

12 years ago, there was a bunch of caps made to a recipie which it is alledged was stollen from a competitor, which they got wrong.

The ones that died on motherboards were usually 2200uF and when made the company had got the recipie wrong resulting in the final cap not meeting the spec they claimed.

 

Hence change them and all was good again.

 

Nothing to do with deliberate design, but actually faulty parts.

Our Philips 5100 microwave oven is coming up to its 30th anniversary.

Consumer law is your friend if under 6 years. But then I thought you'd know that Nick.

If it doesn't sound right and is smoking, why are you still using it?

Weirdly,its more or less functioning normally now, i.e. no humming. crackling or smoke, that is, as long as I don't select the grill and combination at maximum power i.e. an input power of over 2Kw.

 

I've now established that its only the  pre-programmed "One-key-to-hit" Baked potatoe program that relies on maximum power and that produces the symptoms.

 

If  I use the  self-programming keys to select the grill and microwave in combination and restrict microwave power to medium, then all is well.

 

So, I suspect its the top-end of the power circuit that's either faulty in design or the components have gone faulty. I think I may try and replace the power smoothing unit in slower time - I've got a stack of existing repair stuff to do at the moment and, with current hospital appointments, more than enough other commitments to keep me busy. It will have to wait.

 

Nick

For help on diagnosis ,try http://www.ukwhitegoods.co.uk/forumsphpbb3/

Forum run by white goods engineers to help us consumers. There's also a section on what they consider a decent buy. As for invertor technology - how do you thing the magnetron ( thing that produces microwaves ) gets the extremely high voltages needed to work? Can't remember the figure, but I seem to remember it's in order of Kilo(=1000's) of volts.

One thing to look out for in any new microwave, is something like a stainless interior. During use, the food cooking gives off steam. In enameled interiors, the steam condenses and if door closed immediately after use, this turns to water and corrodes the enamel,leading to buzzing as microwaves strike conductive surfaces, short out and burn off yet more enamel.. Cure is to leave door open to allow steam to escape. OR, buy one with stainless interior.

The cooking compartment is stainless, the chassis will just be covered in wisp thickness mild steel primer (If you're lucky) and the inside of the shell case will probably be bare steel.

 

You are right . A steam/cooking oil mix may well be at the root of this, because the vent behind the quartz bulb also leads into the electronics compartment, as of course, does the wave guide tunnel. Faulty design.

 

So, if I disassemble and repair this thing, I fully anticipate a comprenensive clean of the electronic cabin before doing anything else.

 

Nick

At one time John Lewis were selling Panasonic microwaves. Interesting to know whether they still do and whether they offer the extended warranty - the price of that might give a clue as to which components gone.

 

Postscript

 

Ah Hah !  In the sort of price range of my current model , new stuff bought thru JL gets a 2 years Panasonic warranty + optional John Lewis extended warranty for £29:-

 

http://www.johnlewis.com/panasonic-nn-cf778sbpq-combination-microwave-stainless-steel/p230927436

 

 

Nick

Edited 10 August, 201510 yr by Clunkclick