Howdy, I've been trying to fix a power supply in a NAD AV-716 surround sound amplifier. It had other issues with stand by etc, but those seem fixed, I've zero'ed in on the main issue and seem to be a short to ground somewhere.
I've got the schematics for the amp, and measured all the test points, the only part not working correctly is the part that produces the 5v used for all the digital logic. See attached schematic below.
The problem is R927, it gets hot and nearly blows if I dont cut power. The voltages across it are 19v on one side, and 4.9v on the other, the test point should be 18.7 v, so something is shorting to ground to sink that much current. I thought it might be the regulator further along at Q923, but it tests fine out of the circuit. Caps C930 and C929 also test OK out of the circuit. Funny thing is test point where it should be 15.6 v is actually 0v, so I thought R935 was shorting, but it tests OK. I'm completely stumped now what might be going on, so I've posted this as a last resort before I junk this amp.
Thanks for any help anyone might be able to offer.