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Latest post 04-14-2008 9:36 AM by magnushj. 1 replies.
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  • 04-14-2008 3:04 AM

    • stevequinn
    • Not Ranked
    • Joined on 01-08-2008
    • Alice Springs, Northern Territory, Australia
    • Posts 29
    • Silver Member

    Beolab Penta 3 dead

    Hi all,

    I have posted questions related to this issue in the General Forum, but I guess this is the more appropriate forum for things B&O which have died...

    I have now spend hours working on this Penta III amp unit and have had no luck.  I began with the powerlink cables, and the BC9500 and can confidently say that the fault is in the Penta amp.  One day it was working just fine, the next day it was dead - the display works, the light stays green when the relay cuts in, the other Penta works fine on the same cable...

    I dismantled the amp and checked fuses and relay contacts, thoroughly inspected the PCB for damage, noticed that R73 (10K, 1W) had been getting very hot - discolouring the PCB - so removed it and it tested fine.  I then got a handfull of the correct value electrolytic capacitors  and replaced them.  When I plugged it in it was strange - at first there was no change, then after about 1 minute the sound started to fluctuate in volume.  After about 5 minutes it was working normally!  So reassembled and enjoyed listening to music all that evening.  Next morning it was dead again!

    It is now in pieces again, and I have had no further luck finding the problem.

    I tried connecting a non B&O radio to the line-in RCA socket, and there was a very faint signal coming through.  Strangely, when I was outside the house I heard it blast full volume for around a second and then back to a whisper... I heard it fluctuate a little bit once or twice when I came back inside.. 

    Another very strange issue is that the Mode switch on both units makes no difference when switched to L or R.  And I noticed that the balance control on the BC9500 operates normally on the linked passives, and on passives in main room, but on the powerlinked Pentas it only fades both speakers slightly on full L or R - with both having higher volume in the centre position... I de-soldered the L signal wire in the cable, and now the 'good' Penta fades to silence normally with the balance on  L.  Strangely, it makes no difference whether the mode switch is on L or R, even though no L signal is present at the plug!

    I've tested the switch contacts and they are fine.

    Does anybody have experience trouble-shooting these units?  Is there a 'common' cause of failure which might save me going mad??

     Any advice greatly appreciated

    Cheers, Steve


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  • 04-14-2008 9:36 AM In reply to

    • magnushj
    • Top 500 Contributor
    • Joined on 08-16-2007
    • Trondheim, Norway
    • Posts 139
    • Silver Member

    Re: Beolab Penta 3 dead

    Could be a broken trace. Try pushing on the capacitors while observing the board from behind.

    Did you desolder the L-signal in both ends? Is this a home made cable?


    Beocenter 9500+Beolab Penta mk2+Avant+MX7000+Beosound Ouverture+1xBeolab 6000 :)
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