Advertisement



  1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

Avondale m130 build

Discussion in 'd.i.y.' started by longmanjon, Jun 6, 2021.

  1. 337alant

    337alant Negatively Biased

    Johnathan
    You really need to get yourself a higher wattage/Temp soldering Iron the soldering on the speaker terminals and RCA sockets is not good it looks cold to me
     
    Mynamemynaim likes this.
  2. Mark65

    Mark65 pfm Member

    The one time that I have experienced smoke was from the 0R22 resistors
    In my case the amplifier was oscillating due to a poor earth connection in the RCA lead that I was using for testing
     
  3. longmanjon

    longmanjon pfm Member

    thanks Alan, yes sometimes the heat is fine and flows well but on occasion it doesnt, not sure soldering them when mounted was the best option or not as the heat may of dissipated into the chassis.
     
  4. longmanjon

    longmanjon pfm Member

    on checking one of the amps mains disconnected, there is continuity if i place one probe on the 0v (toroid end) of the Cap6 board and parts of the ncc200 plus continuity between speaker posts
     
  5. eddie pugh

    eddie pugh pfm Member

    There should be no continuity between the speaker posts. You should be reading at least 0.5 Megaohms across output terminals.
    The red and black plastic insulators should keep the posts insulated from the metal casework. One of the red insulators looks a bit distressed in one of your photos

    Check that there is proper air space between all your spade connectors, the rear of the mains input socket and the audio input socket

    Do you find the same readings on both amps?

    With the Capo 6 boards disconnected from the NCC200 what voltages are you reading across + - 0v - minus

    eddie
     
  6. longmanjon

    longmanjon pfm Member

    It only seems to be one unit showing strange results, both cap6 boards read 107v
     
  7. Mynamemynaim

    Mynamemynaim 38yrs a Naim owner


    And there lies the problem!!
     
  8. eddie pugh

    eddie pugh pfm Member

    Jonathan

    Do you mean +/- 53.5v relative to the 0volt rail That's a bit on the high side

    I thought you said both boards were smoking Which NCC200 is giving strange results? Is it the repaired one with the burn marks or the one that did not suffer the blow out

    eddie
     
  9. longmanjon

    longmanjon pfm Member

    Hi Eddie yes sorry that is the voltage across - and +, it is the board that had the blow
     
  10. eddie pugh

    eddie pugh pfm Member

    Have you investigated fully the continuity between speaker output terminals Disconnect the speaker output lines spades from the NCC200 and the Cap6 and check the resistance between output terminals

    Then measure the resistance between NCC speaker output terminal and the Cap6 0 volt terminal Compare readings between the two amps

    eddie
     
  11. longmanjon

    longmanjon pfm Member

    There is no continuity between speakers posts when they are disconnected.
    The resistance of the issue board is showing as 141k and the other slowly goes to about 12k, both tested without the speaker cables disconnected
     
  12. eddie pugh

    eddie pugh pfm Member

    Jonathan

    Is the board without issues playing sweet music ? Remember to use some old (dare I say) expendable speakers for initial testing?
     
  13. longmanjon

    longmanjon pfm Member

    Nope tried that one alone and it smoked from resistor 0R22 -3w, not sure what to do now
     
  14. eddie pugh

    eddie pugh pfm Member

    Jonathan

    I would advise you read the following thread It seems poor connections at earth spades and signal earth are known reasons for the board going into oscillation and self destruction
    Damaged NCC200-Left | pink fish media

    If problem still persists then some investigation will be necessary

    Google the "Dim Bulb Test"
    Can you power the amp via an incandescent light bulb (60watts would be good) to effectively drop the applied mains voltage. Be careful with mains wiring Insulate everything properly etc
    If this stops the smoke then it is likely that your bias current is too high.
    This is most likely due to the applied relatively high DC rail voltages of 53.5 volts from your Cap6 boards

    You may get away with reducing the bias current by rotating the bias current setting variable resistor on the board
    It is a small blue component in the middle of the board labelled Set Bias
    You could try turning the little screw anticlockwise to reduce the bias current. If I remember correctly the NCC 200 should run at approx 100mA which gives a voltage of 22mV across the 0R22 resistor
    You will not be able to reach this value with the bulb in series but at least it will give us some idea of what is going on

    The other possibility is that your wiring configuration ( it does look a bit messy) is causing some coupling between input and output which is causing the board to go into oscillation

    I would add that I sold you the boards in good faith believing them both to be in proper order (although I never tested the repaired board) as I had already fitted my NCC220 replacement boards
    I'm happy to refund you if that's your preference as long as you don't totally destroy them. I think though that it would be unwise for you to plug in some new boards into your existing setup as there is a real risk you would damage them. Best persevere and find what is going on with your current setup

    eddie
     
    Last edited: Aug 4, 2021
  15. longmanjon

    longmanjon pfm Member

    dont worry Eddie, im not in the game of blaming others for a process im carrying out.
    i will persevere, it seems odd that when powered there is no problem. so maybe as suggested above it may be to do with the RCA being used.
     
  16. eddie pugh

    eddie pugh pfm Member

    Jonathan

    Now I'm confused What do you mean by "when powered there is no problem"

    eddie
     
  17. 337alant

    337alant Negatively Biased

    The NCC200 has a Bias current of 34-38mA

    Alan
     

Share This Page





Advertisement


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice