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Using NCC200s with Hackercaps.

Discussion in 'd.i.y.' started by Suffolk Tony, Mar 22, 2014.

  1. hacker

    hacker Delicious and nutritious

    Or is it more optimal...? Interesting question! The HackerNAP approach is actually different to my advice above.

    Instead of removing the connection between NCC 0V and the frontend PSU, as I suggested, you might try removing the connection between NCC 0V and the VBE. This would leave the NCC 0V connected directly to the frontend PSU's 0V star, instead of starring on the VBE.

    Which approach is better in this context? I don't know. The NCC200s and HackerNAPs are very different in their VBE/0V design and implementation. I reckon it's a pretty easy experiment to try, so why not give both options a whirl to see if it makes a difference?
  2. Suffolk Tony

    Suffolk Tony pfm Member

    More interesting ideas. The VBE board's rather larger than I'd imagined; maybe there's a simpler solution?
  3. James Evans

    James Evans Bedroom Bodger

    Why not follow the voyager wiring posted earlier?
  4. LesW

    LesW Making electronics make music

  5. chiily

    chiily PFM Special Builder

    That photo is wrong...:(

    When I frst put the amps together I had two earths running to the front end earth on the NCC200...you can just see the two earths in the picture above. That doesn't match the Voyager earthing schema.


    If you look closely you can see that there is only one earth to the front end of the NCC200 in the final amp build.

  6. hacker

    hacker Delicious and nutritious

    Ah, it looks like the Avondale NCC/VBE connection diagram is very different to the hnap. I'd follow Les' advice.
  7. Suffolk Tony

    Suffolk Tony pfm Member

    VBEs now ordered from Les; I'll follow the Voyager wiring scheme.

    Thanks for the help folks!
  8. Suffolk Tony

    Suffolk Tony pfm Member

    Just resurrecting this thread...This was the last bit of proper hi-fi DIY I completed and everything's been working fine, the amp working admirably in a second system. Alas, whilst grovelling about with connections at the back of an AV receiver/preamp (the amp's used to power main L & R speakers) I managed to detach a phono plug, and now the Velleman protection's triggered on the left channel. I've managed to forget most of this stuff now - the inside of the amp looks completely alien to me!

    So folks, I would really appreciate some advice on how best to diagnose the problem. Aware Les is still on the mend so I don't want to bother him. All help and advice gratefully received!
  9. Suffolk Tony

    Suffolk Tony pfm Member

    Perhaps I shouldn't have buried this away in a revived old thread. Any help appreciated.
  10. chiily

    chiily PFM Special Builder

    Tony, reading the manual for the K4700 the red indicates that there is a large voltage on the output, which suggests that the TO3 output transistors have popped and maybe the TO220 drivers too. From what I've read on PFM it looks like you'll have to take the board out and replace the devices.
    Suffolk Tony likes this.
  11. Suffolk Tony

    Suffolk Tony pfm Member

    Thanks Chilly, thought it must be something like that. Damn...
  12. 337alant

    337alant Negatively Biased

    Tony the K4700 will open the relays if it detects more than 1V DC at the output
    Check the DC offset at the output on the board ?
    If its full rail its likely that the output transistors have gone but then you have to remove them and investigate what has caused that ?
    Check your heatsinking of the output transistors before you remove everything as that can be one possible cause of failure

    Suffolk Tony likes this.
  13. Suffolk Tony

    Suffolk Tony pfm Member

    Thanks Alan. During my fiddling I mistakenly pulled the phonos from the preamp output to the amp, and there was a loud crackle...

    I'll check the offset but I'm pretty sure I've blown the output transistors.
  14. 337alant

    337alant Negatively Biased

    good job you had the Vellemans or that crackle could have been your speaker coils frying :eek:
    Suffolk Tony likes this.
  15. flashgo

    flashgo DIY Practitioner

    Tony, check out this post on the Velleman board. The LEDs can stay on even when things are normal. My red LED stays on at half intensity, and everything is fine.

    Suffolk Tony likes this.
  16. Suffolk Tony

    Suffolk Tony pfm Member

    Hi Flash, nice to hear from you!
    I've just renewed the output transistors, haven't set bias etc. yet, but the red now goes out instantly with just a faint glow from the yellows. Reading your link, that's OK. phew...
  17. flashgo

    flashgo DIY Practitioner

    Likewise, Tony! Hope you get this sorted easily. Maybe you'll get the electronics DIY urge again?
    Suffolk Tony likes this.
  18. Suffolk Tony

    Suffolk Tony pfm Member

  19. chiily

    chiily PFM Special Builder

    That sounds promising Tony.

    Check the output offset. Should be in the mVs.

    Good luck
  20. Suffolk Tony

    Suffolk Tony pfm Member

    Oh dear...obviously a bit more than just the output transistors. Now with uncle Les for a good fettling. Strangely, he'd never heard of anyone doing this silly thing before! (Les's two tips to prevent reoccurrence - 1. switch off the amp. 2. switch off the amp).

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