Avondale NCC200 V1.3 Magic smoke !

[Arkless Electronics]

Surely Naim kit will be fitted with speaker protection anyway??????? (That is logic, not experience or knowledge speaking.)

No. But if using the original regulators they have a current limiter that should trip.

 

[337alant]

Personally I have always found the NCC-200 amps to be very reliable
Of course a component can just prematurely fail but a common fault I see is poor attention to heat sinking.

As Jez stated if the 100 ohm resistor has fried then the Driver and Output transistor will also have failed along with the 0r22 resistors.
You have to test and replace any faulty components on the board,
As you do with the new build test the board with the output transistors removed
If you can adjust the bias measuring across the emitter resistor then the board is working and you can refit the output transistors

Alan

 

[GWM]

I just put a pair of NCC200 (v1.3 I think) into my Olive Holden and Fisher NAP250 this morning. The Naim reg boards were set at 40v. I increased this to 44v for the Avondale drop in NCC200s. Set at 35mA. 7 and 13mV DC offset. Sounds good and actually cooler than with the Naim boards. The Naim versions ran warmer than I liked. There is no room for a Velleman unit.
Does this sound OK to continue?
Reassurance would be appreciated.
Chris

Sounds fine.

 

[eddie pugh]

Thanks for all the help guys

My NCC200 amp consists of a transformer which is labelled 33-0-33 at 230v input , feeding two Mini cap 6 rectifier boards each feeding an NCC200 amp board It has a soft start module but no regulator boards or speaker protection modules. The measured voltage at the cap6 outputs under no load is just over 50.3 volts
It was built by Avondale back in 2009 and has done excellent service.


Alan

The 0R22 resistors are all looking pristine so is the resistor down the axis of the copper coil

Am I right in thinking that the driver transistors are the through hole black plastic cased ones ones on the smaller heatsinks TR7 (MJE15030) and TR8 (MJE15031G) Both look absolutely fine no signs of overheating etc The output transistors are a pair of MJ15003HG in chunky metal cans so no telling what state they are in. Both look fine

I'll disconnect the outputs and start taking some measurements in the next day or so and keep you posted

eddie

 

[337alant]

Hi Eddie,
Yes the drivers are TR7 & 8
The only real way to find the extent of the damage is to test
Transistors and those 0r22 resistors often fail without any visible damage

Alan

 

[JimmyB]

My NCC200 amp consists of a transformer which is labelled 33-0-33 at 230v input

My NCC200's are running from a pair of Avondale 35-0-35V transformers so ~50v in theory. However, my mains is at 248V and since the traffo is rated at 230V input, that gives me more like 53V at the output.

@eddie pugh, it's probably not an issue but maybe worth seeing what your mains is at if you've got 50.3volts at the Cap6?

Things fail after all. I used to have a Velleman in a separate box with it's own power supply until I got a larger case and it all fitted.

 

[Suffolk Tony]

I had one of the ncc200 boards go pop for no apparent reason a while ago. Luckily, I'd fitted Velleman so it didn't stuff the drivers. Sent both boards back to Les, who kindly repaired, checked & upgraded both. Been fine ever since.

 

[MJS]

I've built a fair few NCC200s in my time and have only ever seen one fail. It had BUV20 output devices and it took out the emitter resistors but the output device was fine. I can't speak for the MJ15003s as I never used them.

It's worth pointing out that the Naim regulator board, and the SoA circuitry on their amp boards are effectively useless with short circuits. For very low impedances and heavy LF loads they do the job but try shorting out the speaker leads and see how much of the amp still works afterwards

Speaker protection is always a good idea.

 

[gavreid]

If it's any help @eddie pugh I just bought a pair of M130s and so I have my 260z going spare - yours for £400 plus postage. It has soft start module but no speaker protection, which was the standard offering bitd. Les built it, I just wired it. It works flawlessly and everything is in spec.

 

[david ellwood]

There are very few amplifiers that will survive a complete short without self destruction.

 

[Arkless Electronics]

Oh dear!

 

[martin clark]

Ouch!

 

[Arkless Electronics]

There's a spooky face in the debris field 'n all!

 

[James Evans]

Wow, that's a beaut! Proper meltdown

 

[MJS]

That's the sort of lightning damaged amp we occasionally saw at Naim.

 

[Arkless Electronics]

It's looking like scrap.... burnt area on right has gone right through PCB... I can fix it and job will be a gud 'n but it will look bodged to buggery!! Waiting for further instructions from customer...

 

[Vinny]

Out of interest, is there any way, short of massive investigations, to make an educated guess as to what actually failed and started the carnage?

 

[James Evans]

There were several NCC200 boards pulled from amps upgraded to NCC220 in the classifieds here recently, maybe some are still for sale and would be drop in replacements?

 

[S-Man]

SOA failure due to excessive LF transients. Maybe compounded by poor thermal tracking (of TR5) and high output transistor Tj.

The MJE15003 can only do about 5A at 50V, and that's at 25C.

 

[337alant]

It's looking like scrap.... burnt area on right has gone right through PCB... I can fix it and job will be a gud 'n but it will look bodged to buggery!! Waiting for further instructions from customer...

Jez I have some NCC200 V1.3 bare boards If you want one just give me a call
Alan