On Dec 29 2007, 9:26*am, "Torben Espoe"
wrote:
Hi
I *have recently tried to repair a T762, not very succesfull I'm afraid.
The story is this: I was listening to music one day and suddenly the amp
shuts down with at loud POP in the speakers and red light in the status led.
I turn it off and then on again and now there is nothing coming out of the
speakers, other than hum when I turn the volume up to max. After some
checking I find that it can still *switch between video feeds and the main
amps still work if I use direct input.
After some seaching in the schematics I'm guessing that it has to do with a
missing voltage, and sure enough the +12V is missing. After half an hour of
disassembling I have the motherboard out, and I measure the 5V1 zeners and
one is dead. I exchange all 5V1 zeners with 5W types an reassemble the amp,
but now it will not turn on.
The status light is amber, but no turn on. I measure the power on +13V and
find it about 6,5V at D712. it seems that some thing on the +5,6V is drawing
to much current for the poweron trafo.

Does anybody have any sugestions?

Torben

email exchange TWO with 2

Hi I am an authorized Nad Tech, i may be able to assist. if you have
replaced the 5.1v zeners D716,D718 you must change the electro C724.
also these amps have many dryjoints on the frontpanel PCB and also on
the main board, check to see if the DSP board is not shorting to
chassis it has two screws at the top , the bottom of the board is
fixed via two bent chassis clips if the rubber spacer has fallen off
that holds the board above the chassis the board will short to ground,
check the DSP for all voltages you can reference these by reading the
printed overlay on the board were the cables enter, also there has
been good upgrades to the firmware to fix many of the problems with
this amp you may find it a good idea to upgrade the firmware. if you
need any schematics i can help just drop me an e-mail.
Regards Greg