Channel Imbalance in DAC


Posted on Feb 7, 2014

Tested all the resistors and noted 2 resistors` readings were out compared to the other channel (i. e.1. 2Kohm vs 2. 2 kohm). Based on the color codes, should be 2. 2kohm. THought I spotted the problem, repl the `1. 2kohms` with new 2. 2 kohms but the problem persist. The new resistors still reads 1. 2koms and the desoldered ones seems ok reading at 2. 2.


Channel Imbalance in DAC
Click here to download the full size of the above Circuit.

i. e. the resistors seem to have almost halved the value when mounted on the board ! Tested all the resistors and noted 2 resistors` readings were out compared to the other channel (i. e. 1. 2Kohm vs 2. 2 kohm). Based on the color codes, should be 2. 2kohm. THought I spotted the problem, repl the "1. 2kohms" with new 2. 2 kohms but the problem persist. The new resistors still reads 1. 2koms and the desoldered ones seems ok reading at 2. 2. i. e. the resistors seem to have almost halved the value when mounted on the board ! If you`d just said that the resistor measured wrong, I`d have thought that you were a novice who didn`t appreciate that a resistor on the board may not read it`s printed value because there are other components in shunt (parallel) with it. The fact that the other channel measures correctly, however, means that there is a definite problem. The problem MUST be in something that is connected to the 2 resistor terminals, either at the pads or somewhere on the tracks that connect to them. That could be a chain of components, or a single component. There should be be an open circuit between the pads for the problem resistor (when it`s removed), but instead there is a resistance of ~2k6 (by calculation). The most likely cause is a solder string somewhere, probably introduced when you replaced the caps, but it could be a tiny piece of loose solder or cut component lead, or a faulty cap. I`ve even seen (detected)...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Precision calibration standard
    Full-Cup Detector For The Blind
    Portable 230V lamp flasher circuit diagram
    cell_phone
    infrared Help Troubleshooting This Circuit
    Simple Transformerless 5 Volt Power Supply
    camera
    one second audible clock
    5V power supply with overvoltage protection
    HOW TO make a cheap narrowband A/F gauge
    In-Cab Winch Controls and Winch Power Disconnect
    TA2022 and TAS5010 digital amplifier circuit diagram



    Top