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80 HP 912UL will not start

in 912 / 914 Technical Questions 10 years ago

  • Re: 80 HP 912UL will not start

    by » 9 years ago

    Mark & Daniel,

    I have a circuit diagram that I have drawn from disassembling a faulty unit. I have done a double-sided PCB layout and a parts list. I have also found the faults in this particular unit.

    It took me considerable time and effort to obtain this information and I am slightly nervous about giving this knowledge away so that others reading this forum can profit from my hard work.

    That said I am happy to share with the Rotax community to allow owners to save themselves some money.

    Not everyone is going to be able to repair these as some specialist skills and equipment will be required and very few will have a test fixture to verify the amplitude thresholds of the timing switch-over points and the impedance limits of the ignition disable circuit.

    I do not know what the rules are regarding this type of repair. I guess they will vary from country to country. There may be liability issues for anyone repairing one of these units who cannot demonstrate that they followed some kind of process similar to the manufacturer. Even then the cost of defending any legal action would probably kill you financially.

    In many ways it would be cheaper and safer just to build new units. I reckon the cost would be less than 100USD each.

    I will ponder what best to do and let you know.

    Kevin
      
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  • Re: 80 HP 912UL will not start

    by » 9 years ago

    Hi Kevin

    We have done exactly the same thing. The difference is we are not trying to repair faulty modules. We aim to improve the unit to overspec the parts and improve the reliability of the modules. The intention was not to market them to the world but to be able to replace faulty units amongst the group of flyers we have here down under. I am fully aware of the legal responsibilities and what can happen so obviously we don't want to open that can of worms. The replacement cost of the modules here is outrageous and as you say even with upgraded components about 100 bucks to make one for yourself. A few of us have been deeply involved in the electronics game here for decades and have a lot of experience in design and manufacturing so doing layouts and getting boards made is a no brainer. I just want to check that we do have the schematic correct. The one we have done is for the non softstart version. Its funny that the softstart versions do not seem to fail infact we have been scouring australia and also overseas and don't seem to be able to find anyone with a dead one.
    My rotax has the sofstart version which also has different parts installed on the engine to allow it to be used but it would be nice to make a unit that can be selected to be either non softstart or softstart versions.

    Please email me direct and I can send you what we have done. The schematic is done in Eagle 6.6 format a sharing of information would help everyone I would think. We are looking at NOT mounting the units on the engine as it is not a good place for it with heat and vibration especially seeing the electrolytics in the unit are only 85 deg which I find astounding to design it like that especially where it is mounted.

    Mark
      
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  • Re: 80 HP 912UL will not start

    by » 9 years ago

    The non softstart units are made by Ducati I am told but not confirmed as there is nothing written on my modules in the aircraft that the softstart versions are made by Motorini but have not confirmed this

    Mark
      
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  • Re: 80 HP 912UL will not start

    by » 9 years ago

    I received information yesterday that suggests there may be a pair of faulty modules incorporating the soft start circuit.

    Ironically the problem doesn't seem to be with the two electrolytics (which I suspected) but with the SMT components on the back of the board. There is an interesting mix of MELF and chip passives. The layout is very primitive and as a professional I would say not very good for a part requiring high availability.

    It would be easy to upgrade some of the parts but without having access to the production test specification there would be a certain amount of work that would have to be done to determine the test limits.

    I'll send you an email.

    Kevin
      
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  • Re: 80 HP 912UL will not start

    by » 9 years ago

    Hi Guys,

    I just joined this forum having read a lot about this module problem.

    I have an 80hp circa 2006 and hey guess what!! Here in the UK we are suffering the same issues with modules of around this age.

    So as an electronics engineer myself I thought I'd see if I could find the fix. As noted though, they're potted up and pretty much impossible to figure out without a lot of hard work..

    Did you guys ever figure it out? the Carmo electronics guys in the Netherlands are cutting out the back, doing 'something' on the back of the PCB and then re-potting it... though I haven't figured out exact what it is that they do, it sounds simple! Rumour is of replacing capacitors, but I don't know how true this is. I was wondering if the main 'discharge' cap is getting weak but then it's difficult to see how they could replace this in the small amount of space available on the back.. Maybe it's just a cracked ceramic capacitor end cap...

    Please share your thoughts. A group of us are quite keen to figure out a DIY fix, as Rotax seem to be ripping us off with the cost of new modules!

    Thanks
    Andy
      
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