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HackerNap failed

Tony
Another point to be carefull of it to make sure that the 24 caps in your hacker caps are discharged before you start connecting to the board.
there are quite a lot of connections to the Hacker cap and one wrong touch with a charged up cap bank and its majic blue smoke time :eek:
I dont know if it makes any difference but I allways connect up all the grounds first
Alan
 
graham-r said:
Tony

Just a quick question - how discharged was the amp before you connected the B4 ? It is possible that there was sufficient energy left for the amp to go into oscillation when the inputs were swapped. Some amps (Crimson Elektrik for example) are prone to this - I speak from experience, in my case the Velleman did not save the speaker driver !
Click to expand...

Not very, its a good point.
 
337alant said:
Tony
Another point to be carefull of it to make sure that the 24 caps in your hacker caps are discharged before you start connecting to the board.
there are quite a lot of connections to the Hacker cap and one wrong touch with a charged up cap bank and its majic blue smoke time :eek:
I dont know if it makes any difference but I allways connect up all the grounds first
Alan
Click to expand...

Thanks Alan, I have leds on the HackerCap to warn me not to fiddle.
Tony
 
Well been through all my part bins and just getting the shopping list together for whats absent.
The only sourcing problem I have now is with R21, R22 & R23
Vishay Dale 100R 1 Watt 1%, marked CPF1 100R sort of matt pinkish brown.

Tony
 
CPF1100R00FKE14 if they are the same as the ones I have. I think that will mean a Mouser order if your obsessive problem is so serious that you can't abide the thought of a different colour resistor!
 
Thanks, yes Mouser is a pain in the UK.
I can live with a different colour so I can now be sure of the spec and find an alternative.

RS have and equivalent but £5 each, Farnell have three equivalents but US stock so £15 delivery.

Thanks
Tony
 
Hi, Tony

Do they need replacing, or are you just playing safe?

If they don't look burnt and read o/k I would be happy to leave them in.

2x 200 ohm 0.6W in parallel will work or 2 50 ohm 0.6W in series

Pete
 
Evening Pete
Two look fine and measure ok, one is a little burnt and is open circuit.
Was just going to change all three easy peasy until I found how hard they are to find at sensible money

Good idea about // series but
2x 50 ohm 1W in series.

Might just give RS a fiver for one of the buggers :p
 
On discharging the caps before connection - I always put an LED with resistor across the PSU outputs, it gives a visible health check and discharges the caps over a few minutes
 
mr_phil said:
On discharging the caps before connection - I always put an LED with resistor across the PSU outputs, it gives a visible health check and discharges the caps over a few minutes
Click to expand...

Good tip and I have just that but did not wait long enough perhaps, leds are on the inside...
 
I slapped some 4.7K discharge resistors on my PSU the other day.

I have taken out 2 lm317's by connecting up charged smoothers.

Pete
 
Just as a kind of follow-up to my post about oscillating amps, it might be obvious but it is good to make clear that the Velleman speaker protection isn't designed to catch oscillations, unless there is also a DC component present.

The difference between my experience and what may have happened here is that for the O/P the relay was already tripped out after the amp was switched off.
In my case everything was still powered up (a gnd wire came adrift to cause the oscillation), and as a result bye bye (thankfully cheap) speaker driver - the amp survived possibly because it still had a load to absorb some of the power.

Anyone fancy designing a speaker protection device to catch an oscillating amp ?
 
graham-r said:
Just as a kind of follow-up to my post about oscillating amps, it might be obvious but it is good to make clear that the Velleman speaker protection isn't designed to catch oscillations, unless there is also a DC component present.

The difference between my experience and what may have happened here is that for the O/P the relay was already tripped out after the amp was switched off.
In my case everything was still powered up (a gnd wire came adrift to cause the oscillation), and as a result bye bye (thankfully cheap) speaker driver - the amp survived possibly because it still had a load to absorb some of the power.

Anyone fancy designing a speaker protection device to catch an oscillating amp ?
Click to expand...

Thanks for the information, perhaps my amp oscillated when swapping the interconect on the pre amps as the Nap caps were slowly discharging, this destroyed the output stage, raise lots of DC due to the shorted output transistors and then the Vellerman operated.

I will take more care in the future.

Regarding your improved protection circuit, I assume oscilation give rise to massive curents in the output stage, could we detect a volt drop over the output emitter resistors or capacitor bank resistors to fire a relay for disconnection?

Although there does not seem to be any other instances of guys craping out the HackerNAPs, and in my case it may well have been self inflicted through lack of thought.

Tony
 
The problem with detecting oscillations is that you don't want loud music to trigger a shutdown - at the waveform level a loud burst of guitar feedback is just another oscillation!

So you need to build in some intelligence about what is an acceptable average output level, and what is likely to be damaging, as well as the DC detection.

Hmmm, I will think about - you could say something like if the 1second running average power is over half maximum, or the 5s second average over a quarter, you need to shut down. I fear that such a circuit would miss some damaging events, unless it was really sensitive, in which case it might shut down on innocent but loud music.
 
Hi,

The Naim protection circuit could be fitted, but that did have an effect on the music.

I am happy to run mine with out any protection and leave them on 24/7, my speakers have fuses and I have metal film emmiter resistors that blow very quickly.



Pete
 
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