Franke electronic cooker hood

Hi all,

I'm an eternal lurker on the site, having had many questions answered by lots of the great posts on here. I have now however hit a brick wall with my latest problem.

I installed Franke Opera FOP906XS cooker hood in my kitchen a couple of years ago, and it's just developed a problem.

This is the model: http://www.franke.com/content/kitch...handbook/file.res/opera_FOP906XS_HANDBOOK.pdf

It is a complex unit with an electronic control for the lights and multiple speeds.

Now, when i turn the unit off with the control on the front, it makes a loud resonating sound.

I've taken it to pieces, and the source of the sound is the motor continuing to rotate very slowly. The led speed display indicates the fan should be off, but it feels like there is some voltage leaking through to the motor when it is in this state.

The unit comprises of several parts (the attached linked doc has an exploded diagram and circuit diagram of the unit): Motor, transformer, electronic control unit, button and LED display module.

I have a feeling the issue is with the electronic control module, but can't be sure. A replacement one of these is almost £200. I don't want to order one of these, fit it, and find the problem still exists.

Has anyone seen a similar problem in this or a similar design hood? Appreciate it's not a common unit, but wondering if my diagnosis of the symptoms are right or if anyone has any other ideas.

Here's a video of the dismantled unit making the noise...

https://www.youtube.com/watch?v=7Kn_YxvTsxQ

I've renovated my whole house top to bottom, and not had a trade out for anything apart from the gas installation and consumer unit replacement, so I can't bear to get an engineer out for a problem I am sure I can sort myself. Any ideas welcomed!

Cheers
Ady

Can't see the vid - it's private.

I've made the video public, you should be able to see it now.

Cheers
Ady

adeyw said:

It is a complex unit with an electronic control for the lights and multiple speeds.

Click to expand...

Why do they do that?

Does it need electronic control?

Lights - on or off. Simple switch.

Fan - slow/medium/fast - tapped windings, simple switch.

The led speed display indicates the fan should be off

Click to expand...

Why does anybody need a LED speed display? What vital function would they be unable to perform properly without it?

I have looked at the instructions and video but it tells one very little it could be inverter control or simpler brushed motor and much simpler control the number of wires connected to motor means either could be used.

Inverter control means very cheap motor can be used with variable speed however with set speeds it does seem as BAS says a bit of over kill.

However saying that my desk top has a three phase motor cooling the CPU with a little built in circuit to convert DC to 3 phase AC so can't rule out inverter control however the capacitor on motor points to single phase with different configuration of windings to change speed.

Likely using FET's to switch windings and likely a resistor feeding the FET has gone higher than it should.

The FET works opposite to Bi-polar transistor in that it needs current to stop current flow rather than voltage to start current flow.

If you are lucky you may see a burnt resistor but the problem is the resistor may have over heated because the FET is faulty so you can end up chasing ones tail.

With no circuit diagram really you have just two options one is measure everything and try to re-wire with simple switches or the other is new board. Even with new board again it could be a fault with motor over loading FET which has in turn damaged to board again tail chasing.

At price of board compared with price of cooker extractors if it were mine likely I would replace whole unit for a new one rather than trying to repair as so easy to end up throwing good money after bad.