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Entry  Wed Mar 6 20:21:34 2013, Jamie, Update, General, Beatbox pulled from rack 2013-03-06-195232_1060x927_scrot.png
    Reply  Thu Mar 14 11:51:14 2013, Jamie, Update, General, Beatbox upgraded with output whitening, reinstalled 
Message ID: 8245     Entry time: Wed Mar 6 20:21:34 2013     Reply to this: 8292
Author: Jamie 
Type: Update 
Category: General 
Subject: Beatbox pulled from rack 

I pulled the beatbox from the 1X2 rack so that I could try to hack in some output whitening filters.  These are shamefully absent because of my mis-manufacturing of the power on the board.

Right now we're just using the MON output.  The MON output buffer (U10) is the only chip in the output section that's stuffed:

2013-03-06-195232_1060x927_scrot.png

The power problem is that all the AD829s were drawn with their power lines reversed.  We fixed this by flipping the +15 and -15 power planes and not stuffing the differential output drivers (AD8672).

It's possible to hack in some resistors/capacitors around U10 to get us some filtering there.  It's also possible to just stuff U9, which is where the whitening is supposed to be, then just jump it's output over to the MON output jack.  That might be the cleanest solution, with the least amount of hacking on the board.

In any event, we really need to make a v2 of these boards ASAP.  Before we do that, though, we need to figure out what we're going to do with the "disco comparator" stage back near the RF input.  (There are also a bunch of other improvements that will be incorporated into v2).

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