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Re: F&P GW709AU
Fringe,
Be aware that the control board for the GW and IW series appears to be different. The capacitor I found open circuit on our IW709 had no effect on the frequency of the fill circuit, it was there to decouple the clock from the microprocessor. Ours was open circuit, so no fill clock. I replaced it with a 0.1uF (a guess, as the original was not marked) and it is working to this day. (Experimenting with different values had no effect on the fill clock frequency).
As far as I can see, if you are getting a pulse train at the uP pin that varies with air pressure, then the fill circuit is working.
Good Luck.
-Rob.
Re: IW709 Fills up then Error 39
Actually, mucking around with the older controller board has shown that the capacitor is only there for decoupling. The circuit clock speed is around 78kHz and reduces in frequency as the bowl fills.
BTW they were tested on the bench by just applying +5V to the board.
Both control boards now work after removing the offending little bugger(s) and replacintg them with 0.1uF caps.
There must be quite a few of this particular controller with these possible faults on them out there, if I got two. 🙄
– Rob.
Re: IW709 Fills up then Error 39
Well, I think I’ve solved it. I reverse engineered the fill circuit on the main board and replaced a surface mount capacitor, it’s on a test wash cycle now. For those interested in the technical gory details – read on…
The fill circuit consists of a small coil with a ferrite slug pushed up and down by the fill tube air pressure as the water level changes. This coil forms an active part of an oscillator circuit based on a 74C04 IC. Basically the capacitor in this circuit went open. Instead of oscillating, the output was +5V. The problem then became identifying the value of the capacitor, it was an SMD part with no markings.
I assumed most of the other SMD caps scattered around the board were most likely 0.1uF decoupling capacitors, this one was a little larger so I chose a 0.22uf and it seems to have done the trick! ( 😯 ).
Wash cycle is finishing up now, and so am I (it’s 11.30pm local time).I kept the controller board from the original job three years ago and the fault is identical, the same capacitor is stuffed. It’s going to be fixed and piut back into my spare parts ‘stock’. I won’t even tell you what F&P diswasher parts I have stashed away for our dishdrawer!
– Rob. (Hoping that posting this doesn’t invoke Murphy and his law!!) 😉
