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The great "can't fix that" racket


Nick Jones

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10 hours ago, JohnD said:

My appliance god is called Bosch and his other name is tumble dryer.  Yesterday I went to empty it, and found the clothes a bit damp.   OK, there was a towel in there, so turn it back on for another ten minutes.  Fine, it sprang into life, but then stopped as soon as my finger left the 'Start' button.   It no longer latches to 'on'.

The dryer could be twenty years old!  Never given trouble before (there I've really jinxed it)   So parts, like a new switch, may not be easy to find, but I have enquiries out withhtwo Bosch parts suppliers, one of whom has even responded with a request for the machine's details.

So, hopeful.   Anyone know of a Parts supplier to ask?

John

John, I have found everything needed for appliance repairs on good old ebay.

If you have the machine model number or whatever you will find the part is (probably) used by loads of other makes/models. I try to buy OEM stuff where possible. 

20 minutes ago, mpbarrett said:


If it lasts for >5 years then the annual cost is not too bad.....
 

I may have said before, in the student houses I look after, I tend to buy the cheap machines, but with a 5yr cover plan. Not looked recently, but the total was £300 for many years. However, out of the 10? places I look after, I think we have only had 2 claims in 30 years. One of which was at 4 1/2yrs, and they couldn't repair so gave us the machine cost back. (new one was delivered, they dented it on one side, so gave a 25% discount... result for us) 

It is rare for a machine to last less than 8 years, tumble dryers seem to last indefinately but require the occasional bearing change (under £10)

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@JohnD I use a few sites for white goods and general spares for house hold appliances in no particular order and no connection with any.

espares.co.uk

spares4boschuk.co.uk

ransomspares.co.uk

partscentre.co.uk

hope you find what you’re looking for 

cheers John 

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OK, Tumble dryer Pt IV A New Hope.

I've got the dryer out from under the work surface, the top off, and access to the switch.  Multimeter says the switch works!   Three wires to the switch, all white with brown (must mean something) that go to a small circuit board, that holds:

a Relay Which works when I press the switch - I can see it move

two resistors (Brown/?/?/black and Black/Light brown/Dark brown/Red)

a capacitor

and a ?transistor (small metal, can, four terminals)

The board looks a bit hot (browned) around the resistors, but not charred, and one of them has the barrel crackled, and the colour coding bands unreadable (?? above).   I  assume that this resistor and so board has failed, or else the relay, although it clicks and moves?  Pics below.

I suppose I must find someone who can repair the board!

John

 

dryer circ board back.jpg

dryer circ board front.jpg

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Ey-up!    While I've been posting my woes here, I've been to "Just Answers", a website on appliance problems, that puts you in contact with technicians (it says here).    Their techie disabused me of the fancy that I could get into the dryer from the front, so that I persevered in getting it out from under the work surface.   Then he informed me that 'Bosch' dryers were not made by that firm but by "White Knight"  so making parts search on eBay easier.    He then confirmed that the problem wasn't the switch but the circuit board and located one for me!   Few quid and it'll be here in a few days.  Bingo!

Had to pay a small fee to use the "Just Answers" service, but for this amateur engineer it was good value!

John

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I guess the switch itself doesn’t latch? In which case it relies on the relay to latch.

That it apparently doesn’t might be because

- although it moves it doesn’t actually complete the circuit(s) because the contacts are burned.

- there’s a fault elsewhere preventing it (by design) from latching as a safety measure. This might be because there’s a door switch that’s not showing closed or an overheat switch that’s tripped and not reset.

That board hasn’t got much on it. The mystery object is a bridge rectifier I think, though no idea why. There must be some sort of timer too, is there another board or a mechanical one?

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2 hours ago, JohnD said:

and a ?transistor (small metal, can, four terminals)

Item on the board marked W01 with the label next to it BR1 - a bridge rectifier, there to convert AC to DC. Capacitor is likely there to smooth the output of that to "better" DC. Can't quite figure out the orientations of the front/back of the PCBs though to work the circuit out. It's too late and I'm tired.

 

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Hi,
the PCB is AC-powered. The twin resistors are acting as volt-droppers for the DC relay.
The cap & bridge are to convert the AC for use with the DC relay.
The board is dead because you have two dry joints on the relay contacts; fix them with a soldering iron.
Cheers,

Iain.

PS. The relay coil is 48VDC. The 1K resistors look stressed but are functional. It is just the two dry joints that are stopping it from working. Connect the two adjacent Lucas connectors together & it will work without the relay. 

Edited by spitfire6
PS
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Wonderful! Complete information.  I have ordered a replacement board, rather than adding solderingbto my skill set! Yes, Nick there is a mechanical timer elsewhere on the front of the machine.

Going to see tomorrow if my local laundrette offers drying, as I'll have two loads.   

John

Edited by JohnD
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My interpretation, trying to transfer labels etc. to the circuit side of the pcb.

T2 - AC Live in
T3 - Switched AC neutral
T1 - AC live switched output

AC live from T2 feeds one side of the switched relay contacts AND then into the rectifier via R1/R2 in parallel, dropping the voltage that the rectifier gets as input. 
With no neutral at the BR1, there's no DC output from the BR. But if the switched neutral is applied at T3 - bingo we have DC at the coil terminals of the relay - resulting in AC Live at T1. 
C1 smooths the rectified AC to something closer to DC to keep the relay coils happier.

I could be wrong though. I'm not an expert. If you want me to re-flow the board for you @JohnD - PM me and post it to me. Then you have a spare.

dryer.png.eeaef03d7a9e235c68462f7e49ec439c.png

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Gosh! And Gosh, again!  For expertise and help there is nowhere like Sideways! Thank you, YS!   I have a replacement on its way, so I won't trouble you for now.    If, like rhe switch, this board proves not to be the problem, I will return here to the Common Room.of Sideways University, and the Dept. of Household Appliances!

John

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4 hours ago, yorkshire_spam said:

My interpretation, trying to transfer labels etc. to the circuit side of the pcb.

T2 - AC Live in
T3 - Switched AC neutral
T1 - AC live switched output

AC live from T2 feeds one side of the switched relay contacts AND then into the rectifier via R1/R2 in parallel, dropping the voltage that the rectifier gets as input. 
With no neutral at the BR1, there's no DC output from the BR. But if the switched neutral is applied at T3 - bingo we have DC at the coil terminals of the relay - resulting in AC Live at T1. 
C1 smooths the rectified AC to something closer to DC to keep the relay coils happier.

I could be wrong though. I'm not an expert. If you want me to re-flow the board for you @JohnD - PM me and post it to me. Then you have a spare.

dryer.png.eeaef03d7a9e235c68462f7e49ec439c.png

Nice effort, well done. 

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On 10/14/2024 at 9:11 PM, Nick Jones said:

So just to prove that the appliance gods are ever-vigilant and always listening (just like Alexa, Siri et al), I am being punished for suggesting Henry might be invincible.

Our skip-rescue Henry stopped mid flow today. Apparently just stopped as if switched off and could not be revived.

Investigation led to this IMG_6695.jpeg

Cable drum contacts snapped off on the neutral side.

You can see one of the snapped contacts lying loose top right - dunno where it’s mate is….

Should look like bottom left.

Parts are available. I’ve opted for the genuine contact set at a princely £8 delivered….

Dead contact set and it’s apparently undamaged sibling.

IMG_6704.jpeg

Both renewed

IMG_6702.jpeg

Henry lives again!

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Well done, Nick!  And another blow to the Machines, my replacement circuit board arrived today, five minutes to fit, longer to reassemble the dryer and stuff it back under the work surface, and laundry services are resumed!

One in the eye for Planned Obsolescence!

Thanks for all the advice!

John

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Twice I have replaced motors (using OE Numatic) in Henry hoovers at the hotel where my second job is.

 

Bizarrely, in the kitchen there is a hot water tap set too far back, thereby meaning the water doesn't drop into
the well of the sink.
To permanently fix this problem, I offered to move the tap (supplying the parts) for £12 plus VAT
but this was rejected for being too expensive :ermm:

They have a washing machine desperately needing drum bearings but I don't think I will bother tendering a price ...?

 

 

Ian

  • Haha 2
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