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[Gregg]

I am now faced with a dead CE425 which I understand is a custom chip that ADA created.  Looking at how it sits in the schematic it looks like a number of comparators on a single chip which depending on signal level for a given input lights LEDs either green or red.  I'm mildly interested in reverse engineering it.  I was wondering if anyone has actually been able to find ex-ADA engineers / designers who we might be able to tap in recreating the CE425 in some way.

Otherwise, it seems like it would be "simple" given a working CE425 to see how it reacts to given inputs and/or monitor it using a scope in a working MP-2 to determine the relevant signal levels.  It is also possible it is quite more complex than I think.

Gregg

[rnolan]

Hey Gregg, I don't have any connection to the original guys, Kim or Harley might? 

However, you do have one working CE425 in one of the 2 units you are fixing??  The raw clean file I posted for you should tickle most of the LEDs green in normal operation, if you wind up the input signal from that file it (I expect) should push some of them to red and give you some readings re comparator thresholds?  Hopefully it's not more complex.  I wonder if it's possible to use a similar (but available) comparator chip.  It seems simple conceptually, but then....

[Harley Hexxe]

Nope, I don't have anyone to contact, sorry

[Gregg]

Hey Gregg, I don't have any connection to the original guys, Kim or Harley might? 

However, you do have one working CE425 in one of the 2 units you are fixing??  The raw clean file I posted for you should tickle most of the LEDs green in normal operation, if you wind up the input signal from that file it (I expect) should push some of them to red and give you some readings re comparator thresholds?  Hopefully it's not more complex.  I wonder if it's possible to use a similar (but available) comparator chip.  It seems simple conceptually, but then....

The CE425 that kind of works seemed to light the Return A and Return B lights seemingly at random.  I don't know if that is normal or not.  Otherwise that unit's CE425 & associated LEDs seemed to function as I would expect. 

Gregg

[rnolan]

Interesting, I would have thought the returns shouldn't light unless there is signal plugged into them. Although when I look at the schematic in the manual, it seems there is always signal being fed to the loop (which is normal) via the loop level switch and the loop in/out switch either just picks up the main signal (switch out) or selects the loop mixer outputs (switch in).  So if the signal in the loop is passed from send to return with no connections and interrupted when a jack is inserted into the return (which makes sense), then the loop LEDs will always flash.  So probably is normal.  I never pay much attention to the LEDs (until now LoL).  But thinking back when I was making those test files, I do recall all the LEDs flickering. And there is/was nothing connected in the loop.

[rnolan]

Update from the manual [pg 10]: 
[6] Signal LEDs When glowing green: indicates the signal present in that section is 30 dB below clip level. When glowing red: indicates signal present in that section in 3 dB below clip level.

NOTE: The Signal LEDs will illuminate regardless of that section's Status (i.e. switched in or out.)