Recent content by ants2au

  1. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    I have gone ahead and made the change on C40 - added 3.3K in series to C40, which I changed to 100uF.. I now have a good startup delay, of around 7secs.. happy with that. the shut down delay and balance spike, seems to be caused by the filter caps discharging at different rates. not sure which...
  2. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    I am going with putting a series resistor to C40, to slow down turn on, and it wont affect protection calcs.. thats a good compromise for turn on.. ill live with turn off for a while.. its not too bad in terms of speaker thump. thank you for your input Steve, its been invaluable.
  3. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    Oh thats right, we usually have a diode across the relay coil for back emf. but why is it connected to the -ve rail, instead of 0V
  4. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    "'ve seen a similar setup in a sub amp. The cap is solely to prevent start up conditions from triggering the protection circuit, as once it's triggered, power has to be removed before it will start. So discharging it quicker won't turn the relay off." thanks for the feedback. very informative...
  5. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    what if I put a pull down across C40, to allow it to discharge quicker?
  6. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    not even with the text :) now you know how feel
  7. ants2au

    Cambridge Audio P50 - change protection relay on and off timing

    I have a P50, that seems to have a slow protection off timing, meaning when I turn off the amp, there is about 3 sec delay before the speaker relay turns off. to me, it should be instantaneous off, when I turn off the amp. I have tried to decode the schematic, and work out what needs to be...
  8. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Attached. I think I’ll do the other side, so I don’t have to delve back in there again. ‘thank you to all that have contributed..very much appreciated
  9. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    If anyone is interested, this is now sorted. Just to recap, when you know what the problem is, and you know where the issue should be, measuring this problem out dynamically is not feasible, due to the feedback path making things complex. So you go about measuring thing’s statically. so when...
  10. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Ha, r21 was my first port of call, when I first checked this..it’s good. Swapped tr4 and 5, and no change. D3 is good as well. I have also reflowed the whole board..in desperation
  11. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Yes, that is correct.. tr3 has +ve voltage on the base and emitter (As per schematic), but -ve on the collector.. That’s the puzzling thing.. we know what’s wrong, we know what causes this behaviour, but no component (on its own) is misbehaving. not sure what else could cause this.
  12. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Tr1 and 2 have been swapped with the good channel.. they measured ok, but I swapped them just in case. They are good.
  13. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Yes, all measure ok.
  14. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Yes, tr3 has been swapped out.. no change. The base of tr3 (which is connected to the 33k), is reading correct voltage, as per schematic.
  15. ants2au

    Akai 2850 rail voltage on output, but outputs not blown

    Just a bit of background, I’ve had this for about 20years, but it’s been in the shelf, as it had some transit damage when I got it, and kinda left it there, until recently. Cant remember whether it worked or not, but here goes now. One channel has rail voltage on the output so it won’t come out...
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