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hackernap advice thread

yes, disconnecting the rail supply connections to the board whilst powered up and the speakers are attached would blow the output transistor
There is a warning about that from LesW on the NCC200 diag when setting the Bias
You even have to be carfull not to connect the power supply up to the amp board if the cap6 is fully charged

Alan
 
Yep I've now got LEDs on the output cap boards to warn me they're powered up and a big 10 watt resistor with flying leads to short across the rails to discharge each side once I've finished any adjustments ;))
 
timH said:
Yep I've now got LEDs on the output cap boards to warn me they're powered up and a big 10 watt resistor with flying leads to short across the rails to discharge each side once I've finished any adjustments ;))
Click to expand...

I have led's on the front and back end boards also . The back end hold charge for a very long time indeed .
 
I also have the led's but also found an intermittent bad crimp on one on the 0v returns that occasionally became disconnected causing my problem.
 
Tony yes that would account for it working normally one day then failing the next
Still its recoverable so don't loose heart, there is plenty of help here at PFM to get it going again :)

Alan
 
Just reporting back, I now have 4 Hackernaps playing music :) I soldered all the crimps and followed John's recommendations for fault finding, D3 open circuit on one board and blown output transistor on another.
The only problem I seem to have is the bias on one board very slowly but surely climes, could this be due C2 (a Russian tant) leaking?
 
Hi All, I am almost at the end of building my two mono blocks but one of the channels has around 60mV DC offset at its output while the other is 20mV.
The bias is set at 3.3mV and is the same across R26&27. The amp plays music alright but the higher offset concerns me if there is something else wrong?
The offset was even higher at 70mV but I matched the TR1&TR2 hfe's and managed to drop it at 60mV. I changed also the C2 wet tant cap with film one to avoid eventual leakage but with no result on the output.
I use FETlingtons on both FE rails and the +- voltages after the VBEs are perfectly the same now.
Any other ideas where the problem may come from, please?
Do I need to match TR7&9 with TR8&10 hfe's too?
Thank you all!
Ivo
 
James Evans said:
60mV should be fine I reckon.
Click to expand...

It might be - thanks, but the manual says +-50mV and I wonder why mine is higher? What determine this offset, please?
I just don't want to put the amp in my main system if there might be something wrong potentially.
Cheers,
Ivo
 
Hi, I am looking at adding front end hackernap regulation to my ncc200 boards.

They are being built on veroboard and I was wondering whether I could relocate C9 and 11 off the amplifier board and onto the regulator board.

It will allow me to use a film capacitor I have in stock.

I have some 1uF polystyrenes begging to go into this build but I guess they are a bit small in value for they key locations.


Cheers Andy.
 
For NCC200s, 1uF are badly-wrong values for those locations; and locating either C9 or C11 offboard would be a bad idea. Sorry.

If you meant C1,2 4 or 5 - still a very bad idea offboard. Capacitors work for bypassing when they present near-perfect short for AC current. That cannot happen when you add inductance (in the form of lengths of wire or PCB trace) in series, by positioning them remotely from the load they serve.


PS this is also why the very large, axial caps you often see offered and used as boutique audiophile parts for coupling or decoupling (bypassing) are almost entirely a waste of time, regardless of what they may be made of! The loop formed is simply too large. The ideal cap, much like the ideal speaker, occupies no volume and has connections of zero length ;)
 
Thanks Martin, the Hackernaps have 2.2uF in this location but I have some 10uF Wima films I could put in but this seems to be a big value for the regulator. The current value is 10uF.
Any thoughts?
These are the component numbers as on the hackernap schematic.
Cheers Andy.
 
andrewsutton said:
Hi, I am looking at adding front end hackernap regulation to my ncc200 boards.

They are being built on veroboard and I was wondering whether I could relocate C9 and 11 off the amplifier board and onto the regulator board.

It will allow me to use a film capacitor I have in stock.

I have some 1uF polystyrenes begging to go into this build but I guess they are a bit small in value for they key locations.


Cheers Andy.
Click to expand...


I did something like that to my NCCs as I didn't have the Avondale VBE boards. I had to change a few values to get the output voltages right and I have to thank John Luckins for that. An awful lot of the stuff he posts on here is invaluable to people like me :)



 
I tried to build vbes in the avondale style some years ago but both veroboard and etched versions didn't perform.
Can I ask where John's advice can be found?
It does appear that few changes are needed to move from ncc200 to hackernap.
Cheers Andy.
 
Have spotted that on the how to wire it all up diagram in build manual 1.4, some of the wires go to terminal positions that do not match the actual PCB. Bit confusing.
 
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