Fixing reclining chair

Discussion in 'Electricians' Talk' started by Tangoman, May 23, 2017.

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  1. Tangoman

    Tangoman Well-Known Member

    I've a sofa with two electric reclining mechanisms.
    One works, the other doesn't - i decided to try to do something about it.

    Turns out it's the power box (transformer) that's responsible - using the good one, both mechanisms work properly.

    I found a guide here, but I'm slightly confused by it:
    He shows two photos of two different boxes: the top one has output of 24VDC clearly shown on the label, but he replaces with a transformer with 24VAC output.


    My transformer is identical to his except it is 230VAC/0.5A input.
    Output is 24VDC/3A

    Help!
     
  2. Tricky Dicky

    Tricky Dicky Screwfix Select

  3. Pollowick

    Pollowick Screwfix Select

    You may be confusing transformer and Power Supply ... The box is the power supply with a 24 V DC output, with a transformer inside.

    The circuit board on page 3 shows a bridge rectifier that changer AC into an unsmoothed DC waveform and then the capacitor adjacent to it smooths it out to DCish.

    On Page 4 it shows a 25 V ac 38 VA transformer in there originally and that is replaced with an equivalent.
     
  4. sospan

    sospan Screwfix Select

    If you can run a cable, you may be able to take a feed from the output side of the working power supply/chiar to the other chair. As long as you don't operate both chairs at the same time, you should be ok.
     
  5. Tango - no not, not, NOT try and replace the transformer inside your existing PSU.

    Don't do it, man. Chust don't.

    It ain't worth the hassle.

    In any case, what makes you think it's the trannie inside that's gorn boom? That is relatively rare. What is far more likely is that you've damage the wire coming out of the PSU or else as it enters the wee pluggie at the end.

    If your PSU is really knackered, then do as Tricky says - I'm sure you can find a lot cheaper too if you look.

    Any chance of a piccie of the PSU? Show the unit with label, and also the end pluggie.

    You say it's 24VDC and 3A output?
     
  6. Tangoman

    Tangoman Well-Known Member


    Thank you! Yes, I completely overlooked the circuit board's involvement!


    @Deleted member 11267: thanks - thats a little cheaper than I'd seen previously: £60 for replacement power box
    @Tricky Dicky: Yes that would provide the power, but no means to respond to the switching mechanism - I could cannabilise it for the transformer inside as I guess it will be similar given the same output.


    @Devil's Advocate : Cheapest I've found a transformer so far is £15 and I'm sure I'll find cheaper. The exact part used above is less than £10, but I can only find one source and they charge £12 shipping. So if I can make it work I'm paying £15 rather than 60, which is better than £100 which is what I originally saw for the power box.

    You're right - it's a bit of hassle, but nothing scary - worst case scenario is that I waste the new trannie. The power box fails to power the OTHER mechanism, so clearly the fault is internal - it MAY not be the trannie, it could be a wire inside that has come loose, but unlikely as no moving parts. It COULD be the circuit board though - I'll dismantle it and get the test meter out.
     
  7. If you are simply assuming it's the trannie - with nothing to back that up - then you are a wee bit silly.

    :)
     
  8. What type of plug is on the end of the DC cable - is it a standard co-ax type, usually around 5.5 outside diameter?

    You can buy a brand new PSU of this spec for less that £15.

    (If you buy a trannie that isn't the exact one, chances are it won't fit inside the case; it'll either be too small - so packing needed - or too big in which case you are stuffed (see what I did there? "In which case you are stuffed"... Fnuurrrrrrr... ))

    If the wire connections are in different places, you are doubly-stuffed.

    Don't do it, man. Just buy a complete unit for £15.

    Post a photo of the unit and the DC plug.
     
  9. Tangoman

    Tangoman Well-Known Member

    If I could buy a unit for £15 I'd jump at it - so unless you want to point me in the direction of one that can work with the switching unit...

    Packing is hardly an issue - too large is more problematic for sure, I may end up having to use duct tape to hold the box shut.

    I've posted a link to the device above - where it says £60.
     
  10. Still a little confused - that unit also holds the control circuitry for the touch pads? There ISN'T a simple separate PSU giving 24VDC?

    Are you assuming it's the trannie chust because you found that repair guide on t'net? Have you tested it with a meter - is it truly dead?
     
  11. Mr. Handyandy

    Mr. Handyandy Screwfix Select


    He said he'd put the good one there and it worked with the good one swapped in.
     
  12. Tangoman

    Tangoman Well-Known Member

    The power box has 3 lines connected - the mains power supply, the connector to the switch and the power to the motor. As shown in the link above.
    The switch is a simple up/down.

    If I switch the power box with a good one, then everything works so it is DEFINITELY something inside this power box.

    Inside this power box is a transformer and a circuit board, so it is one of these which has failed.

    I'll rule out the circuit board before ordering a new trannie by testing the transformer output voltage, but reading around it seems that it is a common failure.
     
  13. Ah, I see.

    Sorry - a replacement 24VDC PSU ain't what you need then.

    I agree - it's clearly summat inside that box. Or the sockets on it.

    Seriously - if you are going to the hassle of sourcing and replacing the trannie based on the assumption it must be this because (a) it has to be 'something' inside the unit and (b) it seems to be a common issue, then I can only wish you good luck and hope that it does indeed turn out to be this part.

    You don't have a test meter? A few seconds with one of these would have confirmed the issue.

    On the positive side, it does look as tho' there's plenty of room inside that case for different sizes of trannie. I would NOT buy a normal 24VDC PSU - such as those for laptops, etc - and hope to crib the trannie from there, tho', because most modern PSUs are 'switching' types so rectify and regulate their outputs in a different (more efficient) way, so's there's every possibility (but I don't actually know) that the trannies used will be different.

    Personally, I would visit a hardware store (or our hosts) and buy a cheap digital multimeter, carefully reconnect that trannies to the mains and connect the meter to its output (set meter to AC volts and '100v' or above) and see if that trannie is truly dead.
     
    Pollowick likes this.
  14. Tango, do you have the specs of YOUR trannie - does it have model codes on it?

    If so, post that on here, please, so's we can look further.

    Another alternative IS to buy a laptop-type 24VDC 3 or 5A PSU (which can be got for around £14) and to wire its output directly to your unit's circuit board. The place to connect it would effectively be across the large smoothing capacitor (getting the polarity right, of course...). I'm not sure if it would then make sense to remove the rectifying diodes or would they be ok staying there.

    Tbh, tho', this is what I would do; (1) confirm (using a meter) that it IS definitely the trannie, and then (2) spend the £20 - including silly postage costs) for the CORRECT trannie.

    It seems weird that you'd risk getting a cheaper trannie, saving only a few squid, when you then have the hassle of making it fit.

    One more thing - if it IS the trannie (ie it's totally dead) then try a continuity test across the primary (mains input) and secondary (output) coils. If it's the 'mains' side wot's 'open' circuit, you could try very carefully peeling the plastic tape layer away from that side and you might chust find a thermal fuse sitting in there. If it has one, I would lay a bet that it's the fuse wot's gorn. And they'll only be pennies to replace...

    Meanwhile, get yersel a meter and post the trannie's ID on here, please.
     
    Pollowick likes this.
  15. Tangoman

    Tangoman Well-Known Member

    Lucky not to get a shock from that capacitor - 24h since last used and it still made quite a spark!


    20170525_114057.jpg 20170525_114119.jpg 20170525_115342.jpg
     
  16. MGW

    MGW Screwfix Select

    I know our chairs will run from 2 PP3 batteries they are fitted because should you have a power cut while the foot rest is up it is very hard to get out of the chair. Mine uses what I would call a speaker plug for power to the chair, and have run for years, however of the 3 chairs and settee one chair has had problems, it is where the cables go into the ram, and slightest movement can cause chair to start or stop working, it would be very easy to blame the wrong item.

    The link says made in Italy, but also says 110 volt and has USA colours.
     
  17. Bob Rathbone

    Bob Rathbone Screwfix Select

    From the pictures the power supply is a standard linear type with a low frequency (50Hz) transformer. Before you start to spend money I suggest that you exchange, swap the transformers to see if the fault moves with the transformer or stays with the chair. If the fault is still on the same seat, then it's the chair motor or control switch that is faulty. I have a 2 seat setee with these recliners, the PSU is a switching type. I suggest that if you are sure that the PSU is faulty, that you take a look on E Bay.
     
  18. Mr. Handyandy

    Mr. Handyandy Screwfix Select

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