justanalogue

Metric Halo ULN-2 schematics?
« on: March 27, 2021, 09:43:43 AM »
Hello,

A friend of mine has a Metric Halo ULN-2 with distortion on the outputs.
Can't find any schematic's on the Interweb, so can anybody help me out?

Thanks in advance!

Kind regards,

Willem.


Khron

Re: Metric Halo ULN-2 schematics?
« Reply #1 on: March 27, 2021, 09:55:16 AM »
Whip out the oscilloscope. Surely the output section can't be THAT complicated...

DAC's - some opamps for low-pass filtering - some more opamps to drive the outputs. And optionally some muting transistors, perhaps.

Well-focused and well-lit (but flash-glare-less) photos of the affected area might also help.
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justanalogue

Re: Metric Halo ULN-2 schematics?
« Reply #2 on: March 27, 2021, 09:59:29 AM »
Thanks for the swift reply, basically I am hoping for damaged elco's on the outputs, had a Focusrite on the bench once were those exploded, turned out they plugged the jacks in to the outputs wo were already connected to a mixer WITH phantom power on.
Schematics would be helpfull.

Kind regards,

Willem.

Khron

Re: Metric Halo ULN-2 schematics?
« Reply #3 on: March 27, 2021, 10:03:20 AM »
That's a "maybe". Could even be one missing supply rail for the output opamps (seen that caused by a shorted tantalum in an Apogee Ensemble Firewire).

There's a good chance the datasheet for the DAC / codec chip may have examples of output reconstruction filters (low-pass filters); it's somewhat doubtful they would've strayed too far from that.

https://content.head-case.org/monthly_2020_02/0E248782-9C6B-4BBF-B276-148676D65308.jpeg.68ef1593ae71634a9a586a3cd8fdd45f.jpeg

Looks like the DAC is next to the big fat electrolytics and the four red polypropylene caps. Can't quite tell what chip it is, but likely an AKM job (as the two ADC's). Some NE5532's for the output filters (note the light grey / white ceramics - likely pF-range C0G / NPO).
« Last Edit: March 27, 2021, 10:22:06 AM by Khron »
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

justanalogue

Re: Metric Halo ULN-2 schematics?
« Reply #4 on: March 27, 2021, 11:28:10 AM »
Thanks a lot for your information!

Kind regards,

Willem.

Khron

Re: Metric Halo ULN-2 schematics?
« Reply #5 on: March 27, 2021, 11:31:13 AM »
Not to brag, but...



Where there's a will, there's a way...  ::)
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans


 

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