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Q1.R.C.D. tripped by disco decks.

Zoomup

I am checking a Citronic item. It is a double deck disco console called a Stereo Popular. It is unpowered and needs a separate audio amplifier. It causes a 30mA R.C.D. to trip off. This is an irregular problem. Sometimes the turntables will rotate normally, one showing a change of speed sometimes which is noticeable when a record is playing. The only mains in is to a small Holden & Fischer toroidal transformer. No internal fuses blow, and all insulation resistance tests show infinity resistance. There is a ground/earth connection from the E.L.V. side of the power supply board that has two 1,000 micro Farad electrolytic capacitors. I wonder if one is breaking down and causing a leakage to earth? But that is only on the E.L.V. 15 Volt side. Any ideas please? 

Z.

Edit. Add. The unit dates back to the 90s I believe, but is of very good quality. It plays vinyl records and has two permanent magnet D.C. turntable motors with speed controls for mixing.

I can't understand how a fault on the 15 Volt side of the power supply circuit board can cause an R.C.D. trip.

It looks like this, although the image is of a mono version.

www.ebay.co.uk/.../403346023714

Z.

Parents

  • I can't understand how a fault on the 15 Volt side of the power supply circuit board can cause an R.C.D. trip.

    Maybe a short between the primary and secondary of the transformer? - the circuit the completing via the ELV side's PE link.

       - Andy.

  • in reply to AJJewsbury

    Although thinking about it, that should have shown up on the insulation test, presuming the ELV's "Earth" is the LV's side's c.p.c.

       - Andy.

  • in reply to AJJewsbury

    The transformer seems to be o.k. No connection by wire insulation breakdown from primary to secondary at 500Volts. The primary windings are 0-120V 0-120V. 103 and 97 Ohms respectively.

    The two secondary windings are reading 13V and 13V off load.

    The two 1000 micro Farad power supply smoothing capacitors test at about 950 micro Farads each by an Atlas tester.

    I am still puzzled.

    Perhaps this unit operated o.k. on a non R.C.D. protected supply and it is just now that I have found a fault. I did change the R.C.D. and the same fault occurs.

    Z.

  • in reply to Zoomup

    Eurica! I believe the problem is due to the disco desks being supplied from one R.C.D. protected circuit, but the amplifier is supplied by a different R.C.D. protected circuit.  When the screened audio cable is installed between the decks and the amplifier one R.C.D. does not like that and trips. The screen is earthed.

    An inline digital multimeter set to A.C. milli-Amps shows zero current when installed in the decks' earth wire (C.P.C.).

    Z.

  • in reply to Zoomup

    Why can't we quote any more? Thinking

    In line multimeter (rather than clamp meter) is a bit brave! I have to admit, however, to doing the same on a 2-way (flickering) lighting circuit. Current was 1 mA when the switches were off.

  • in reply to Chris Pearson

    Brave, Oh yes. That's me all over. Inline is more accurate to  my mind Chris. I started off on a 20 Amp range, then switched down to 200mA in stages.

    Z.

  • in reply to Chris Pearson

    Use the cursor to highlight text you are interested in and a new "quote" option appears.

    Although when I try it I keep getting an error message, and have to delete the quote before my reply will work. 

  • in reply to Chris Pearson
    Chris Pearson said:
    Why can't we quote any more?

    You can - either as 2400 says you can highlight and use the Quote pop-up button, or just copy & paste into your reply the bit you want to refer to, select that and use the Formats->Format->Blocks->Blockquote to make it a quote.

       - Andy.

  • in reply to Zoomup

    Eurica! I believe the problem is due to the disco desks being supplied from one R.C.D. protected circuit, but the amplifier is supplied by a different R.C.D. protected circuit. 

    Humm. Any ELV current between the two boxes still shouldn't be finding its way through either RCDs coils ... unless there's another fault somewhere.

       - Andy.

Reply
  • in reply to Zoomup

    Eurica! I believe the problem is due to the disco desks being supplied from one R.C.D. protected circuit, but the amplifier is supplied by a different R.C.D. protected circuit. 

    Humm. Any ELV current between the two boxes still shouldn't be finding its way through either RCDs coils ... unless there's another fault somewhere.

       - Andy.

Children
  • in reply to AJJewsbury

    Having plugged the unit into just one supply via just one R.C.D., albeit a 100mA type, there is no tripping at all and the unit is working well. I am still puzzled as to why the tripping happened in the first place. The unit showed no earth leakage at all with my in line multi-meter.

    Z.

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