St. Channel made a pop sound, then made the smoke smell.

[Jermbob]

a Stereo channel made a pop sound, then made the smoke smell, on a 6k. It no longer passes audio. I swapped every card besides the dynamics and eq, with no effect. I have plasma meters, and when I have the power off they usually meter something, but no longer on this channel. Also the routing matrix LEDs no longer work.

[sintech]

Hi, looks like you may have a short circuit, maybe on the 11v rail (this would explain the lack of LED's) And the motherboard protection is kicking in. On the mono channel this protection is Pico Fuses and Zener Diodes and rectifier Diodes, guess the stereo is the same kind of thing with maybe bigger values.

You can buzz the power rails on each card to find the short.

[Jermbob]

I have a good idea of how the short happened. Some tech put the multiplex card in to place, without the standoffs. Do I need to replace the fuse, or will it start working when the short is found?

[sintech]

Hi, I bet the diode on the 11v rail is maybe burnt or open circuit.

I would power the channel on an extender and check all the voltages at the extender side and the channel side post pico fuses and diodes, see what juice is passing, and what is not.

[sintech]

This is the arrangement on the Mono module, it's bound to be similar.

[Jermbob]

Thank you so much! I'm wishing I had an extender right now. I'll take a look! 

[Jermbob]

Is this where I should be looking?

[sintech]

Yes, F1 and F2 are the 18v bipolar rails, (check these with the meter) with the two Red Zener  diodes to 0v (check these are not shorted)

The two black diodes relate to the 11v rail, (Diode test these)

[michaeldtech]

If you do not have an extender card then remove the modules from the bucket and you can test the module in situ.  And the mux card would not really be able to touch anything on the fet if not on the standoffs.  Did you find evidence of burn around there?
Mike

[Jermbob]

I replaced a diode and F1 fuse, and now it works great. Thanks guys.

[Jermbob]

If you do not have an extender card then remove the modules from the bucket and you can test the module in situ.  And the mux card would not really be able to touch anything on the fet if not on the standoffs.  Did you find evidence of burn around there?
Mike

The multiplexer card shorted the Vca card. Had to recap the card. Works great now!