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DIY Armageddon.

Discussion in 'd.i.y.' started by sq225917, Mar 10, 2012.

  1. sq225917

    sq225917 situation engineer

    Nothing out of the ordinary internally, there is a varistor over the N/L that isn't in the Naim part and there's an inline mains filter from Schurter, but other than that it's the usual recipe, 500va transformer and 2 x 0.1uf caps for the phase shift network.

    I might put a DC blocker in there as there is space and I can see the washing machine doing it's thing on the output with my scope.

    [​IMG]

    [​IMG]

    [​IMG]

    Entire set for Armageddon clone build+ annotations.
    http://www.flickr.com/photos/59684834@N08/6823360144/sizes/l/in/set-72157629553367709/

    Not only does it look the part but it frankly kicks my Hercules into the weeds.
    Case and sled from FlatP of this parish, a perfect match for the Naim shoeboxes already in my system.
     
  2. sq225917

    sq225917 situation engineer

    Ooops. Yeh i potted the transformer with epoxy, there's a 20mm standoff coming through from the underside of the sled with a big nut on top. This is cast into the centre of the traffo keeping everything locked in place. It all sits on a 3mm Sorbothane sheet to keep noise down.
     
  3. Retro

    Retro pfm Member

    All the other Geddon clones I have seen use a resister in series with the Red motor wire and the caps on the Blue motor wire. I understand that this is how the Naim circuit is made. Perhaps I am mistaken, or you have chosen to do something a little different. Either way, please explain.

    Glad it's working well!

    Graham.
     
  4. 337alant

    337alant Negatively Biased

    Its a 110V motor so it doesent need a resistor, SQ is using a transformer with the correct secondarys (2x55v I think), if you want to knock the motor down a bit further to say 85-90V then yes you can use a resister
    If you supply it with a 220v AC supply you need a 6.8K 2.5W resister on the red phase, but then it wouldnt be a geddon :D

    Alan
     
  5. sq225917

    sq225917 situation engineer

    Alan is correct. I don't need the dropper resistor because the output is already 110 volts.

    I did try it pretty much all the way from 80 volts to 110 and there's absolutely nothing to be gained by dropping the voltage, except crappy torque. If you have exactly the correct caps for your your actual motor it runs silent so no need to drop the voltage to reduce hum- there's none to speak of.
     
  6. martin clark

    martin clark pinko bodger

    Quite. Qith 0.22uF caps using a resistor drops the voltage and reduces the vibration in the motor but has no effect on speed stability. 4K7/3W part is a good start - leaves plenty of torque for start-up but makes noticeable difference to 'quieten' the motor which will run at 70-80v. If you don't mind a push to start then as much as 6K7 is useable. It's well worth a play for the 10p it costs. Or you can start with 0.20uF and ignore (or play to suit taste)

    Incidentally I think using the wrong cap value is why some supplies then use different voltages on the phases to 'correct' the apparent resulting issue...
     
  7. ChristianThomas

    ChristianThomas Registered User

    sq

    What's the output socket you are using and what is the dia of the pins?
     
  8. sq225917

    sq225917 situation engineer

    Martin, that's certainly what the Hercules appears to do. There's a shunt on one output, lift that and it runs the same voltage on both phase, as opposed to 20+ volts difference normally. They run a 0.22uf cap as standard, mine was slightly over that value. tut tut.
     
  9. Retro

    Retro pfm Member

    Back to my original question, the Naim Geddon uses a resistor in the red motor wire and a 110V Tx secondary, so that circuit is a "true geddon" surely?

    Graham.
     
  10. 337alant

    337alant Negatively Biased

    Graham
    Yes that is The true Geddon but if you read threads 5,6 again, the answer is there ;)
    Simon is using 2 x 0.1uf caps in parrallel to give 0.2uf which give a near as damn it 90 deg phase shift to the motor so there is virtually no vibration and you get good torque and start up by having the higher voltage.
    Looks like Naim used a standard value 0.22uf cap and then compensated for the vibration by using a resistor. two wrongs dont make a right :D
    Very nice neat job by the way SQ :cool:;)

    Alan
     
  11. Joe

    Joe pfm Member

  12. sq225917

    sq225917 situation engineer

    Yup, it's the Maplin 4 way, audio locking, line chassis plug and socket.

    Re the Geddon, Ynwan has an Olive version and that deffo uses 2 x 0.1uf caps, in fact the same Silver Siemens caps as on the 323 cards. I haven't measured them to see exactly what they measure as, my Wima's are 0.100uf, matched from a big bag.
     
  13. Retro

    Retro pfm Member

    Hi Thanks for the replies.

    Firstly, SQ very neat job definately.

    Alan I still don't feel that we have got to the bottom of this issue.

    Naim use a 110V TX and a resistor and a cap. I personally don't buy that they put a resistor in because that couldn't get a .2 cap as a preferred Value. I'm sure they would have put a pair of .1's in just as I, SQ and many others have done.

    I know Naim are not perfect, but they do seem to be particular and very thorough about what they do include in their circuits. I am curious to find out why it's there. Is it just a method of reducing the voltage out of a Naim standard TX or perhaps there is some kind of damping effect going on?

    Either way, I went from a Valhalla to my clone and it is a substantial improvement in scale and wallop.

    Regards,

    Graham.
     
  14. MartinC

    MartinC pfm Member

    Graham,

    You beat me to it! I am sure that the restor adds a damping or some interaction with back EMF. As you say, Naim aren't going to cripple what is their only LP12 motor supply for the sake of a capacitor value.

    You might also want to play around adjusting the cap values slightly, I found that the value that has the least motor vibration was slightly off from the standard.

    Cheers
     
  15. ChristianThomas

    ChristianThomas Registered User

    SQ, a bit more on those Maplin sockets. Are they on a 16mm mounting hole or is it something smaller? (ie. are they CB connectors?) And could you have a guess at the diameter of the pins if you haven't got a set of calipers.

    Thanks in advance.

    Christian
     
  16. sq225917

    sq225917 situation engineer

    Christian, I don't have a set of calipers that i could use to measure them, 16mm looks about right for the backs, i wouldn't like to guess for the pins, about 2mm.
     
  17. ChristianThomas

    ChristianThomas Registered User

    Thanks sq, that'll do fine.
     
  18. laverda

    laverda pfm Member

    I found an improvement by 'switching' (110v) the secondaries.... leaving the primaries (the transformer) live all the time :- the inrush of current at switch on (through the primaries) takes quite some time to 'settle down' before giving best results.
     
  19. sq225917

    sq225917 situation engineer

    I leave it on all the time, I just plug the motor in when needed.
     
  20. johnnym

    johnnym pfm Member

    Reading this thread I realised that by very first project a few years ago of building a geddon wasn’t quite right. I had for some stupid reason connected the transformer secondaries in parallel rather than in series (the transformer in question has dual 55v secondaries). The TT always needed a bit of a push to get going but somehow it worked all the same. Now I’ve connected transformer in series, my meter reads 122vac rather than 110vac. The motor on my TT states a voltage of 110 50hz so I don’t wan’t to connect the 122vac for fear of knackering it. I tried adding the usual 3.3k resistor and the reading came back around 121vac. Do I just need to increase the value of the resistor if so by how much or could it be my multi-meter giving odd ac readings?
     

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