AML ez1073pre Phantom LED Not Working, What to check?

[funkymonksf]

Good morning, afternoon, evening,

I just finished a pair of AML ez1073pre's (500 series). One is working just fine, but the 2nd's phantom power LED is not lighting up. Could you suggest what I should look for?

I'm obviously going to check solder joints and signal and DC continuity, but I wonder if there is anything else I should be looking into. Goal is to have a game plan before I dive in. Just waiting on my 500 series extension jig, A MUST!

Schematic attached.

Thanks!

Brice a

 

[TwentyTrees]

Hi Brice,

First thing I'd check is whether the LED is in the right way round. This can be hard to judge when soldered in and leads clipped, but if you look very closely you may be able to see whether the internal structure is oriented in the same way as your working unit (which is an absolute boon to troubleshooting!). Once that's confirmed, you can just use your multimeter to ohm out the very small part of the circuit relating to that LED (just the short bit top left of the schematic) and make sure there's no bad joints or duff components - current limiting resistor R28, switch 4, and the pins connecting that switch sub-board, comparing to your working unit as you go. Divide and conquer is the way. Obviously you can do this with the units unpowered and out of your 500 series rack.

Assuming everything's in the right place and there are no bad parts or joints, it might potentially be a bad LED.

One question - the phantom power LED isn't lighting up, but is the switch activating phantom power correctly?

Good luck!
Andy

 

[funkymonksf]

Thanks Andy,

The LED orientation could very well be the issue. I actually haven't checked when I was getting 48v when activated.

I really appreciate the response.

 

[funkymonksf]

LED was upside down. I feel so fortunate, as there couldn't be an easier fix. Thanks!

 

[TwentyTrees]

It's very easily done! Glad to hear you got it sorted. I've a pair of ez1073pre modules that I do rather like.