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hackernap advice thread

Thought I'd post my own version of the BOM as it may be of use to anyone looking to build from scratch or replace/change components. Probably only of value to those in the UK and possibly Europe. The prices (which link to the associated webpage) include a component for delivery if charged, but don't include VAT. There was little opportunity to shop around for the best price as most things were only available from a single supplier, usually Mouser.
 
Finding it hard to find the transistors MJW21194G , RS don't stock them but they do have MJL21194G. Is it ok to use these instead. CPC stock these too with free delivery for online orders.
Regards Keith
 
Same transistor in a different package, so should not be a problem (unless you have already drilled holes based on the dimensions of the MJWs)

/U.
 
Thanks. I haven't got round to heat sinking yet. It takes me ages to build things, but I will get there in the end.
Regards Keith .
 
Hi chaps,
I may have made a boob with my resistors,

for R8 22K, I have got a bunch of RS components : 683-2787
and R2,R28 ect, the 100K I got : 165-0498

They are tiny in comparison to the other resistors and the links from the 1.7 BOM pdf bring you to the Mouser homepage now.
Any advice?
Cheers
Justin
 
Hopefully the Mouser product database is just having the weekend off :D.

You can extract the Mouser part number from the URLs. So

R8 is MF1/4CCT52R2202F
R2, R28 are SFR16S0001003JR500

which you can still search for. Both your alternatives look good to me, but you best wait to have that confirmed by someone that knows what they're talking about ;).
 
One of my HN boards went "blue smoke of death" recently so I replaced main transistors, drivers and 0r22 resistors. Thing is when I fired it up again yet more smoke. What might I have missed?
Tim
 
This has happened to me once on my own Hackernap, and a couple of times on other peoples NAP circuit based designs that I have mended. You really need to check a few other components that might also have failed before refitting, just in case. Like you I remove and check the drivers (TR7 and TR9) for a short between any of their three terminals and for functioning diodes, that is base to collector and emitter diode on an npn, the reverse on a pnp. Often they haven't all failed.

I do the same on the output devices and then in circuit check all resistors and diodes, including D3 from R19 up, lifting just one end of the component if necessary. I also remove Tr4 , 5 and 6 to be sure these aren't damaged and check the bias pot and R12 are OK and also that C15/C3 haven't gone short circuit. I've had failures on occasion on each of these active devices, but rarely on more than 3 at a time. It really is best to take the transistors and diodes off the board to test them IMHO as it allows for easier and proper checking of the resistor values around them. Don't forget to check R24, the loss of which can cause instability at HF. It is tedious to have to be so rigorous, but it pays off at switch on.

John
 
Hi all just had blue smoke from the neg rectifier diodes!! and very high DC offset, Working fine last night but not tonight working thro the usual checks. Going over the original circuits on accoustica and Les's schematic, C2 is reversed from the original schematics (originally C6) I'm using a 68uf wet tant would this make a difference
 
Feed back cap should be as stated by Keith
47uf, 68uf, 82uf is no problem

what offset do you have
What rectifier diodes did you fit?, it could be that the inrush current at switch on has popped them if they are low current ?.
A photo will help
Alan
 
There is a very small negative voltage across C2, which means it should have its + lead attached to the HackerNAP's 0V. Even if it was reversed I'd be surprised if it caused any damage, the voltage/current is truly miniscule; it's almost certainly not the cause of your rectifier diodes blowing.

I'd suspect a short somewhere in the frontend -ve rail. Did one of the VBE caps fail and go short? Did the IRF6910 fail short? How about something on the HackerCAP PSU board?
 
Thanks for the reply's it will be the weekend before I can get at it.
C2 was just something I noticed and wondered about, didn't think it would be the problem since no one else has mentioned it.
No caps dramatically failed but will check later, not checked the IRF610 yet. The HackerCap seemed OK as the whole thing worked fine the previous evening with a bias of 3.8mv.
Rectifier diodes QSpeed LQA16T300
 
The QSpeed LQA16T300 diodes are good and what I use myself, just check they were the right way round and the bodies not touching
http://www.flickr.com/photos/69508926@N05/6709036653/in/photostream/
disconnect the power supply from the amp board and fit 2 new diodes then check that is OK
If your DC offset is full rail voltage then you have blown an output transistor if its still milli volts then all may be OK
If your C2 is the wrong way round, remove it, check it and replace it in the correct orientation. Check for a strait short on the amp board between 0V and -Ve, start testing components for differences between that and the good board.
If its all OK reconnect the power supply, you could use a 1K 5w resister in line with +ve & -ve just in case, start testing voltages.
Alan
 
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