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Thread: Rangehood circuit board
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3rd Oct 2017, 04:33 PM #1Most Valued Member
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Rangehood circuit board
Hi all, this circuit board is out of a glem rangehood and the parts are no longer available.
The only thing that I can see that might be the problem is the transformer PT-6329A, looking underneath the board looks like it has been a bit hot.
Neither the lights nor the fan work so I am guessing that this transformer powers the other components on the board, I have had a look on the net
for one of these with no success.
An easy solution will be to fit another switch and wire it straight to the fan but l would rather avoid this if possible.
Does anyone know of an alternative transformer that I could buy from somewhere?
Or have any other ideas what to do?
cheers shed
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3rd Oct 2017, 05:49 PM #2Pink 10EE owner
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I found this image
http://radiomehanik.ru/images/produc...ges/1738_1.gif
Would two buck converters work? Adjust to the required voltage? Although they output DC.Gold, the colour of choice for the discerning person.
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3rd Oct 2017, 08:06 PM #3Most Valued Member
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Buy a new rangehood.
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3rd Oct 2017, 10:03 PM #4I break stuff...
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Not sure that a DC output would pose a problem in this case, if those 4 diodes directly under the transformer in the last pic are doing what I think they are - it looks like they might be doing some rectification, which is then smoothed by the two caps below them?
Hopefully one of the electronics gurus will be along shortly to confirm or deny that theory...
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4th Oct 2017, 03:01 PM #5Most Valued Member
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Shed,
I would confirm whether the transformer has failed before trying to source a new one. In my experience they very rarely fail. The heat discolouration looks quite normal to me. It's more likely to be one of the semiconductors (labelled U or Q on the circuit board) or a capacitor.
Is this a variable speed rangehood? I can't understand why a rangehood needs such a complex control circuit.Chris
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4th Oct 2017, 03:48 PM #6
Agree that discoloration looks normal.
The label on the side indicates 230 - 11 volt, a competent technician would be able to put a multimeter on the circuit and confirm if the transformer is working or if it is a fault somewhere else in the board.
If you do not have the skills training to work on the equipment I would suggest you engage the services of a technician as it requires working safely with mains voltages.
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4th Oct 2017, 04:08 PM #7Philomath in training
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Have you checked that the switch is actually functioning? I had one on a lamp go toes up the other day. Something about moving parts and voltage means they can fail after a time.
Michael
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4th Oct 2017, 07:47 PM #8Most Valued Member
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Thanks for the replies and hints fella's,
I think l will put some juice into it and measure the output voltage from the transformer as Chris and droog suggested.
Chris I hope you are right about "the semiconductors (labelled U or Q on the circuit board)" they would be easy to replace,
spoze if I replace them all I might get lucky
Michael it has 4 momentary switches with a light in them, it has 3 for the 3 speed fan and 1 for the lights that shine on the pots.
I checked the power to the board before pulling out, juice was going to it but nothing at all worked, not even the little lights in the switch buttons.
If anyone else has got any clues then spit it out please.
thanks, shed
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4th Oct 2017, 08:02 PM #9
Found reference here:
https://www.elektroda.pl/rtvforum/topic2659539.html
From the pictures on that site it appears there is an inbuilt fuse or thermal cutout in that model transformer, it may be housed in the lower skirt around the transformer.
If you have volts to the primary side and none on the secondary side do a continuity test on the primary. If no continuity check if you can locate the fuse / cutout and check the continuity on that.
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4th Oct 2017, 08:10 PM #10Most Valued Member
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5th Oct 2017, 04:17 PM #11Most Valued Member
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Not a bad days wages
droog gets the elephant stamp, yay droog
the picies tell the story, l went and got another part from the local Jaycay shop, the problem was a 115 deg x 2 amp thermo fuse and as you can see it
was very sneakily hidden behind the blue tape, the closest part that Jaycar had was a 133 degrees x 10 amp, the bloke in there reckoned that the fuse
works by heat and not by the amps drawn through it so l banged it in there.
Soldering that hair was a challenge for this shaky old welders dog.....l have put the board back where it came from so now l just need my young bloke
to get back up in the roof and switch it back on.
Thanks fella's, shed
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5th Oct 2017, 09:22 PM #12
Job well done.
Past experience tells me these are a common problem.
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22nd Oct 2017, 02:02 AM #13
Hi Shed,
Sorry to be late on this one, I'm catching up on posts at the moment.
Those thermal fuses are designed not to reset after they have activated. Whilst the one you have used to replace the faulty one will work, the transformer will get a great deal hotter than it would normally. The flat box type fuse are designed to be mounted in as close a contact as possible to the heat source, ie the transformer primary winding, whilst the one that you show in your pictures is designed to be clamped to the heat source, such as the heater plate in a coffee machine or electric smoothing iron.
Somewhere I have a number of the box type fuse, if I can find them I will post back here and let you know. I don't remember what the operating temperature of them is, but I used to use them on similar transformers, 240 volts input, 6-0-6 volts or 9-0-9 volts output at 250 ma.Best Regards:
Baron J.
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22nd Oct 2017, 10:28 AM #14Most Valued Member
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Thank you Baron, l thought that the tranformer may be faulty if it gets hot enough to blow that fuse, or was the fuse faulty?
It is working fine now so l think that l will just let it go and if it stuffs up again l will remove it and l will get a better transformer and mount it external to the board.
Cheers, shed
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22nd Oct 2017, 10:56 AM #15
I have replaced many of those thermal fuses with no other faults elsewhere in the circuitry, it is common for them to fail even when used in conditions for what the original designer intended.
The transformer manufacturer put them in as a fail safe for their transformer to cover themselves from warranty point of view, the designer of the overall circuit in which it is used also provided protection with a fuse on the circuit board, if the transformer develops a fault it would also be protected by the fuse on the board.
If I was repairing the board for my own use I would not be concerned by removal of the thermal fuse. I am not advising to do that as it would void warranty etc, etc,
Any external transformer will most likely not be fitted with a thermal fuse and you would still void warranty etc,etc.
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