Uniti Atom.
Functions normally when first turned on, with a quiescent mains draw of approx 50ma (@230v input)
When it warms up, I get a 0.5volt 4MHz oscillation on the L channel output and the quiescent mains draw goes up to 300ma.
This, of course , leads to further heating (even with no input signal) until eventually the thing is too hot to touch.
Anyone seen this?
M
Functions normally when first turned on, with a quiescent mains draw of approx 50ma (@230v input)
When it warms up, I get a 0.5volt 4MHz oscillation on the L channel output and the quiescent mains draw goes up to 300ma.
This, of course , leads to further heating (even with no input signal) until eventually the thing is too hot to touch.
Anyone seen this?
M
Clearly the rig is oscillating. If you have at hand those cans with liquid air that quickly ice small pieces, try it first in large sectors (say 5cm by 5cm) until locate the place where the fault is being generated. Thus, try reducing the area covered to circumscribe the piece. It may be a transistor, an IC or a capacitor. Rarely a resistor causes those kind of faults.
How do you know, are you scoping it?
If so, show a screen capture.
What happens if you disconnect load?
Are you using a Monster Cable or similar "audiophile" one?
Naim claims Class AB amplifiers, which typically use Zobel networks at the output for stabilization.
Add one across speaker terminals, any change?
Typical values are 0.1uF ceramic + 10 ohm 0.5 or 1W resistor.
Brochure claims the Amps are similar to other Naim ones, get and post a schematic to check the Naim design "philosophy", each designer has his own preferred traits, we might guess something from that.
Thanks for your reply, Juan. The zobel components were the first thing I checked (not easy, this thing is a layercake construction). I'm fishing for someone who has "been there and done that". There's nothing special about the poweramp, it is just sandwiched amongst a pile of digital fruit. Waiting to see what Naim have to say as the problem appears to be endenic (lots of hotties). Tried all sorts of loads - 8,600,open - no difference.
OK.
Can you identify the power amp input?
If so, what does slapping, say, 220pF across it do?
Try to find some comparable Naim amp schematic (say, between 30 and 60 W RMS or so) and post it here, all I found was a "250" which to boot required registering.
Can you identify the power amp input?
If so, what does slapping, say, 220pF across it do?
Try to find some comparable Naim amp schematic (say, between 30 and 60 W RMS or so) and post it here, all I found was a "250" which to boot required registering.
at least, the R side is operational, it allows a point of comparison.
I will trace the signal from the input and compare with the other canal
I will trace the signal from the input and compare with the other canal
