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~1996 DBX 160A meter problems
« on: March 18, 2020, 05:04:03 PM »
So  i have a dbx 160A ( not the newer AD) and the level meter is just lit and not responsive.
The gain reduction meter works as expected.

most likely ruled out power supply and the quad comparators as problems
anyone know which opamp drives the meter in this/know a common point of failure when the meter does this?

The unit still works fine and sounds the same it's just the constantly lit meter is driving me crazy

the lack of a schematic from dbx is making this a PITA. I've looked at 160x and xt schematics and that kinda helps

on input mode the meter will not respond with or without audio input, it is just constantly lit
on output mode with no audio input the output gain will change the level meter
on output mode with audio it will not respond until compression happens and then the output moves but it just looks like the reduction meter

things i have done to troubleshoot:

Checked voltages:

 +24 is +28V
-24 is -28
+15 is 15.1
-15 is -15.22

%15 is acceptable i think

i have two of these units so:

1. i tried using the transformer from my fully working unit in the broken one - no Change
2. there are test points to check voltages i jumped these from one unit to the other to try and bypass the power supply on the bad unit- no change
3. reflowed solder for the 3 potentiometer on the front plate and the meter cal on the back- no change
4. i swapped the whole faceplate assembly from the working unit to the non working unit - no change

ok, so there is a problem with whatever is driving the meter a bad op amp? a bad cap that supposed to be blocking dc that isn't?
did i miss something?

There are known unknowns,
and unknown unknowns...


Re: ~1996 DBX 160A meter problems
« Reply #1 on: March 18, 2020, 11:22:03 PM »
IIRC the 160A is  similar to the 160XT

Schematic is here

You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


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