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Thread: Advice please on valve amp issue

  1. #1
    Join Date: Mar 2017

    Location: Melbourne

    Posts: 445
    I'm Karl.

    Default Advice please on valve amp issue

    Hi guys a freind has a Mastersound compact 845 amp with B&W 805d speakers.

    He is slowly losing volume when the amp is on before it cuts out.
    I was wondering if any of you valve experts know what the issue could be before he sends it off for repair.
    He would like to try crack it himself as its mid Jan before the guys can fix it, so no music over xmas for him .
    He has tried changing valves but still happens

    Thanks

    Karl


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    CTC Classic 301 , SPH bearing and Hanze Hifi HAT CPS-2 all analogue power supply / Tenuto Mk2 mat / custom Panzerholz and Kewasinga articulating plinth / Track audio isolation feet / Reed tonearm / Audio Technica ART 9 / 2 box BigBottle mk3 phonostage with Clarity cap CMR and NOS Telefunkens valves / Croft 25R preamp with upgraded 12BH7A line stage and NOS 1956 RCA valves / Croft 7R monoblocks with NOS 56 RCA valves/ Dynaudio Contour 30i speakers / Spotfire interconnects and speaker cables / Merlin Scorpion mains block / Rhodium mains cables / Marantz CD DAC /

  2. #2
    Join Date: Oct 2016

    Location: London

    Posts: 313
    I'm David.

    Default

    At a guess I'd say it's the slow start bias circuit. If the timer circuit goes faulty vol would slowly fade as the bias reduced to the start up mode. But there's lethal voltages of well over 1000volts inside so unless he's suitably qualified he should leave very well alone. Apart from experience you need insulated gloves rated at 3kv

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  3. #3
    Join Date: Oct 2017

    Location: Coventry

    Posts: 130
    I'm Mick.

    Default

    Hi
    How long does it play for, whats the time-frame ?

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