Dimplex Opti-Myst fires

Discussion in 'Electrics UK' started by Neil B, 13 Feb 2010.

  1. mr rusty

    mr rusty

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    Thank you AlastairE for your very prompt reply
    I have checked individually each pin on each lamp holder in turn and back to connection block for the transformer - all appears ok
    I have also checked out for any possible short circuit to earth on the lamp holder itself - nothing faulty found (via ohms)
    There is a feed leaving the pcb via the relay to transformer which I can hear working, and 240volt at the connection point for the feed to the transformer but no DC voltage from the transformer to the light connection block.
    This is the new transformer as the original is discontinued and this the compatible replacement.
    http://www.savemylight.co.uk/htv250c2.html#.VhwFKiyFM3w

    If you still feel the lamp holder is the problem could you advise how the easiest way to get to it, many thanks for all your help
     
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  3. AlastairE

    AlastairE

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    That Transformer you have fitted is an ELECTRONIC Transformer--It does NOT put out a DC Voltage, but an AC Voltage at around 50-100KHz depending on load...
    --You'll notice, it says, 11.5Vac output at 250W on the device itself.....

    --You'll not measure this with standard DC Meter! a Multimeter/AVO on AC Range May work--But I expect it will Mis-Read wildly due to the frequency those things run at! AC Range on Multi-meters are set up for accuracy at 50/60Hz RMS Sine wave, that 'Transformer' is not actually a transformer inside--Its a Switch-Mode Power-Supply operating at very high frequency, many times what test-meters are designed to read on AC Ranges and not of a Sine wave format--Its more of a flyback pulse wave.

    Another issue is it may not output anything unless there's a load connected to it, or may operate in 'burst-mode' making any test-meter readings meaningless.....

    --Best use a Test-Lamp (a known good halogen from the fire) on two leads to confirm there's power coming out of it.

    Connect a test-lamp directly to that transformer--and mains the mains side. If the lamp works, the 'transformer' is OK. Don't bother with a meter for this type trans.
     
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  4. mr rusty

    mr rusty

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    Thank you for that info. I will do that test tomorrow and let you know how I get on.(y)
     
  5. ban-all-sheds

    ban-all-sheds

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    That, typically, is very much what SMPSUs do not do. That may well be the frequency in the inverter stage, but not the output.
     
  6. AlastairE

    AlastairE

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    Err-IF you had continued to read that post--the second line says--'
    --You'll notice, it says, 11.5Vac output at 250W on the device itself.....

    We are talking Lighting Transformer--Electronic, These things are seldom rectified and nearly always produce an AC output as described. Never seen one intended for Halogen lamps thats DC output.

    --Thats why it says '11.5V AC' output on the device itself..... Why would maker use a rec and caps etc, maybe a choke or two--When they Don't NEED to--Thats just extra expense they don't need to spend for no advantage for the intended application!

    AC works just as well to light incy- bulbs as DC.

    In Lighting supplies--Only LED SMPS Supplies designed for the purpose--are DC--and a little more expensive due to the extra parts, too.
     
    Last edited: 13 Oct 2015
  7. mr rusty

    mr rusty

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    Hi AlastairE. I have just done the transformer test as you suggested and it is working fine. The lamp lit up like blackpool illuminations.
    Does this now mean it is definitely the lampholder do you think? Would you be kind enough to advise the best way in to replacing this before the entire fire goes through the conservatory window. Thank you so much for your invaluable help in this annoying matter.
     
  8. JohnW2

    JohnW2

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    I don't think BAS was suggesting, or even implying, that they produced DC. Rather, I think he was (I would say correctly) pointing out that your implication that they produced AC at their output of 50 kHz - 100 kHz is not (at least not usually) correct.

    Kind Regards, John
     
  9. AlastairE

    AlastairE

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    There'll be 4 or 5 lamp-holders/sockets--I Doubt they have ALL failed--At the same time.....

    This suggests that there's a failure between the transformer and the connections to all the sockets--worth pulling all the wires from the connection-block checking and re-installing....

    The sockets themselves can be replaced one by one by removing the screws and pulling upwards....
     
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  11. AlastairE

    AlastairE

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    Hi John,
    --In the ones Ive seen/dismantled, the Inverter transformer secondary is connected direct to the output leads, therefore whatever the switching frequency is the output frequency, and as the inverter Tx is a rather small ferrite cored thing, this is going to be many tens of kilohertz to pass the power required.
    --This is one reason these things produce so much 'hash' for Radio reception--HOW they get certified is a complete mystery to me! They really Are that cheap and awful....

    Best regards,

    Al
     
  12. mr rusty

    mr rusty

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    Hi AlastairE .
    Not sure how to get the screws out as they are inserted from underneath and the lamp holders are not individual that I can see. Hope these photos show what I mean.
    The drawer is out as far as it will go
     
  13. AlastairE

    AlastairE

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    With that type, you'll have to remove that steel tray they are fitted to--From Underneath....
     
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  14. mr rusty

    mr rusty

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    ok, will have a go at that tomorrow. Together we will have rebuilt this fire, maybe we should give lessons to Dimplex!
     
  15. AlastairE

    AlastairE

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  16. mr rusty

    mr rusty

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    Thanks AlistairE. you're a star! (y)
     
  17. mr rusty

    mr rusty

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    DSCF9492.JPG DSCF9493.JPG DSCF9495.JPG AlastairE
    Thought you might like to see this. After taking out the lamp holder unit I discovered what is hopefully the only reason for the lamps not working. I haven't got any further just yet but will let you know the final outcome.
    It's obviously a manufacturing error as you can see that the insulation has been clamped through and this resulted in meltdown of the connectors. . This is actually the second manufacturing fault I found as when I originally took out the transducer there was a similar problem.
    I shall be sending these photographs to dimplex but don't expect a good reply, if any. I have found their customer service and after sales service to be appalling.
     
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