+ Reply to Thread
Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: SAFETY ALERT, Perspex cased BMU (Balanced mains unit)

  1. #1
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 5,825
    I'm Alan.

    Default SAFETY ALERT, Perspex cased BMU (Balanced mains unit)

    I have found a serious safety problem with an encased BMU. DO NOT OVERLOAD YOUR BMU, this applies equally to any transformer.

    The unit in question is a perspex cased BMU, I stress that this transformer has been subject to OVERLOAD.

    The enclosed 1kVA transformer was held in place with glue and expanded foam packing, with no ventilation or method of heat transfer whatsoever.
    Every power transformer has a specified temperature rise (above ambient) at full rating, usually 55 degrees Centigrade.

    Think about that.. 55 degrees above ambient. Usually a transformer has free air around it that conducts heat away from it.

    This is what I found:



    I don't know what loading had been used on this BMU but the transformer became so hot that (1) the foam packing has melted, plus most worryingly (2) the transformer insulation and the input wiring PVC insulation has melted, causing a short circuit. The input wiring was held against the top of the transformer by the frankly shocking construction employed.

    The unit was causing a trip to operate in the consumer unit (mains supply).



    The melting point of PVC insulation is >140 degrees C, so not a great situation.
    Unfortunately due to the construction method a visual inspection of similar units is nearly impossible.

    The minimum advice for anyone using one of these would be to operate it at nowhere near maximum rating.
    Last edited by Firebottle; 07-07-2021 at 06:31.
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  2. #2
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    WTF!
    SS
    CD Teac VRDS25X(Audiotuned) DAC Caiman SEG+15V PSU+Dorado DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe/Ebony PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10

    VALVE
    PRE
    Croft Epoch(Modified) AMP Sondex S100 (Modified) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Reference XO DECKS Garrard301/401 (Bastin) Mat Teunto Bearings 301/401(Bastin) Plinth Moldovan/Bastin Arms 3009/3012(Ikeda Ag wired) SME V 12 PSU Eagle+Tachometer MC Ag Meister v2 / Royall N SPU's CABLES Arm Yannis 420.5 Litz+ Speaker 10mm Cu + WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostage Paradise(4 Box Modded) / EAR 834 Clone (modded)

    www.facebook.com/wakefieldaudio



  3. #3
    Join Date: Sep 2009

    Location: west mids, UK

    Posts: 3,015
    I'm Phil.

    Default

    thanks so much for highlighting , nearly bought one of these in past .
    When words are many , sin is not absent, but he who holds his tongue is wise . prov 10

  4. #4
    Join Date: Jul 2009

    Location: Hampshire, UK

    Posts: 3,501
    I'm Adam.

    Default

    Shocking (sorry…)

    Frankly I’m not surprised. I’ve seen pictures of the inside of one of his ‘Statement’ products and it was appalling.
    Engineers: fixing problems you didn't know you had in ways you don't understand.

  5. #5
    Join Date: Dec 2018

    Location: Neath, Wales

    Posts: 1,452
    I'm Shane.

    Default

    Jesus fucking wept! You could destroy earth with that thing.

    S.
    Home Hi-Fi Chat UK (Facebook Group)

    Shane Lonergan.

  6. #6
    Join Date: Apr 2012

    Location: South West of England

    Posts: 309
    I'm Will.

    Default

    Oops, wrong kind of insulation
    Radford Revival
    www.radfordrevival.co.uk

  7. #7
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 5,825
    I'm Alan.

    Default

    Having received feedback from the manufacturer it is confirmed that the design principle is one of containment under fault conditions.

    It is considered not to present a fire hazard but my advice of under-running the unit stands.
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  8. #8
    Join Date: Jul 2009

    Location: Hampshire, UK

    Posts: 3,501
    I'm Adam.

    Default

    Looking at the pictures, my advice would be to not plug it in under any circumstances!
    Engineers: fixing problems you didn't know you had in ways you don't understand.

  9. #9
    Join Date: Nov 2014

    Location: Caterham,Surrey

    Posts: 61
    I'm Stewart.

    Default

    Quote Originally Posted by Firebottle View Post
    Having received feedback from the manufacturer it is confirmed that the design principle is one of containment under fault conditions.

    It is considered not to present a fire hazard but my advice of under-running the unit stands.

    Sounds very familiar. cladding?

  10. #10
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 5,825
    I'm Alan.

    Default

    A statement from the manufacture:

    'Our current BMU comes with the option of a thermal cut out and we speak to each potential purchaser about the calculations required to check the power consumption of the equipment that they want to use the BMU with. The BMU is rated at 1Kva. We recommend that you do not use beyond 70% of that capacity. If we are not satisfied that the BMU will be used within that limit, we won't sell it to you.'

    Bear this in mind if you buy one second hand.
    Last edited by Firebottle; 07-07-2021 at 06:32.
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

+ Reply to Thread
Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •