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Aging electrolux RM 4505 Could i make a new pcu


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I hear that my dear ol' fridge (c yr2000) is now obsolete. The pcu has packed up (again)...Pity..the replacement cost £300 only 3 years ago. Mine does not recognise mains so only runs on gas or 12v. Not the end if the world but inconvenient.


New pcu not available.. new fridges certainly - but £1,500 at least. I wonder how many of these fridges still exist? Me wonders about possibility of manufacturing a pcu.


The device is coated in shellac.. to stop moisture getting in ..and inquisitive people like me. But you tube says a heat gun melts shellac. So maybe I'll have a go?


Is it worth it? If I discover the inner secrets will it benefit mankind.. or at least those who have RM 4505s


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I had a similar experience many years ago with my RM6505 fridge in a 2004 motorhome which is still in use !

I suspect the fridge (auto 3 way) is similar to yours. The fridge suddenly would not work on mains electricity. I was put off by the conformal coating on the pcb - so purchased a new pcb for about £110 I recall.

I did subsequently dig around through the coating and identified the problem as a 240v relay failing. So maybe this is your problem as well ?

Good luck - ps fridge ran perfectly on new pcb and is still in use now !

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Unless you have previous experience of designing and etching PCBs, the answer to your question is probably no. You would have to access all of the PCB components to identify them and reverse engineer the circuit. Not an easy task.


The coating is unlikely to be shellac, which is a varnish made by disolving flakes of resin in alcohol. However as Silicongyro alludes the coating is probably some sort of synthetic resin, which may not melt easily. Application of high temperatures from a heat gun could possibly cause further damage.



Assuming that it is the PCB, and not the 240V element that is faulty, you would have nothing to loose by attempting a repair instead of a rebuild? Again Silicongyro has suggested the 240v relay as a possible cause. It would be much easier to eliminate that possibility, before embarking on such an ambitious course of action.




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Some conformal coatings are designed to be reworkable and so you may not need to remove the coating before resoldering. Do this in a well ventilated area though as the fumes are not pleasant. You would need to clean off the surrounding area with IPA or similar to get a reliable solder joint.

A board 20 years old will have probably been made with tin/lead solder rather than lead free. If you use your soldering equipment professionaly, don't contaminate your soldering tips etc. and use the appropriate tip temperature.


If I have a particularly old board to repair, I usually look out for dry joints on large components and connectors, dried out electrolytic capacitors (sometimes have signs of bulging cans) and mechanical switches and relays.


Obvious signs of burning/overheating can be a good indicator but the fault may be somewhere else.




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  • 2 months later...

This guy and his company are very good at electronics repairs for Fanmasters, Cascade, Truma PCB repairs, etc. see :



If he knows the RM 4505 PCB is no longer available he may start a new line in repairing them or supplying remanufactured, just as he has for the Carver, etc.


Then again he might not, but maybe worth a try?






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