Hello,
I have a NAD C356BEE wich won't turn on. No light at all. No relay click when i push the standby button.
There is only 2.1 volt on the 5 volt rail. On the other rails (+ 55 volt etc,) there is no power.
I disconnected all cables from the power board to the other boards. But still only 2.1 volt on the 5v rail.
I looked at the schematic but cannot find the solution.
Any suggestions?
Thanks in advance.
Nicootje.
I have a NAD C356BEE wich won't turn on. No light at all. No relay click when i push the standby button.
There is only 2.1 volt on the 5 volt rail. On the other rails (+ 55 volt etc,) there is no power.
I disconnected all cables from the power board to the other boards. But still only 2.1 volt on the 5v rail.
I looked at the schematic but cannot find the solution.
Any suggestions?
Thanks in advance.
Nicootje.
Well, how is the standby +5V generated, and do you see anything suspicious in the area? Might be no more than a bad cap, out-of-spec resistor, bad solder joint or similar.
Thank you sgrossklass. I am sure it will be one of the causes you mentioned.
But it is really hard to measure such things in circuit and i do not want to solder all those components out of the board to measure.
I have the schematic of this amplifier. The +5 volt is generated by a tny274. I do not have an osciloscope to look at the signals.
Do you have tips for me how to find the broken component?
But it is really hard to measure such things in circuit and i do not want to solder all those components out of the board to measure.
I have the schematic of this amplifier. The +5 volt is generated by a tny274. I do not have an osciloscope to look at the signals.
Do you have tips for me how to find the broken component?
TNY274 is a SMPS controller with built-in switching MOSFET by the looks of it. I suppose the circuit roughly follows the "Typical Standby Application" as given in the datasheet? So then you should also have a flyback transformer with the typical Schottky rectifier diode and a smoothing capacitor on the secondary side, presumably electrolytic. I'd take a good hard look at this cap (ESR meter, or just parallel a known-good one). Knowing NAD, it's not likely to be an oversized premium part (I'd suggest Panasonic FR or similar), and a dead cap usually results in low and/or unstable output voltage.
The passives dropping TNY274 supply voltage are also worth a look - if it's a capacitor dropper, that cap may be down in value, not an uncommon sight as standby supplies often see little in terms of mains filtering and are subject to all sorts of voltage spikes.
I wouldn't think it's the zener, these generally either work perfectly fine or are dead short.
The passives dropping TNY274 supply voltage are also worth a look - if it's a capacitor dropper, that cap may be down in value, not an uncommon sight as standby supplies often see little in terms of mains filtering and are subject to all sorts of voltage spikes.
I wouldn't think it's the zener, these generally either work perfectly fine or are dead short.