Elements Troubleshooting Guide

You’re finally at the end of your Elements build and it’s not working right. That sucks. Have no fear; we’ll help you get it fixed.  This guide is set up to help you isolate the issue.

Testing Limitations

Troubleshooting a build is tricky, particularly when it's a 500 series build. You'll need to be able to power and send signal to the unit while having access to the PCB. This can be done by using an extender jig or having a multiple space rack you can empty to gain access.

If you don't have a way to safely power and test the unit, consider sending it in for flat rate repair.

Op-amp issues

The op-amps are 50% of the mic-pre circuitry. Start by trying to rule out an op-amp issue. If you have some, try a different op-amp. Any API 2520 compatible op-amp will do. If your mic-pre works with the substitute op-amp, contact us for replacement. 

Power Supply

Power your unit and measure your supply. Start by checking the fuses to see if they are being tripped. If the edge card side reads the appropriate DC voltage and the PCB side does not, that relay is being tripped by a misplaced or shorted component. To test the +48VDC phantom power fuse, you'll need to engage the phantom switch. Fuses are reset when the unit is power cycled off then on.

Common reasons the fuses trip:

• Bad op-amp (remove op-amp and see if the fuse still trips)
• Polarized capacitor installed backwards
• Q600/Q601 swapped or installed backwards.

The DI relay is ON by default and is turned OFF by inserting an unbalanced instrument cable into the DI jack. In this default ON state, the DI relay should read -8 VDC and +15 VDC at its power pins. If your DI relay is not powering properly, you may notice that your DI works fine and your XLR in does not work at all. In this case you need to examine the relay circuit and confirm all components are installed correctly and all solder joints are good.

Check your supply voltages using the chart below. Note the GND designations at pin 5 and 13. You can use either as your ground reference for your common/black probe. Try measuring your op-amp supply pins with the op-amps installed and uninstalled. There should be no change. No AC signal is required.

Power Supply Test Points PDF Download

Mic-Pre Signal Testing

To isolate the issue, we’ll trace the signal through your pre and figure out where the signal stops. For TP 1-5 and TP 12-13 we're going to measure the differential signal. Simply put, we’re going to measure the AC voltage by placing one DMM probe on the hot signal (+) and one probe on the cold signal (-) noted by the two points on the test point PDF. Polarity of the test points in not noted because it's not important. Just measure AC voltage across the two points. After the input transformer, the signal becomes single ended. Meaning there are no longer hot and cold signals at opposite polarity. There is simply one signal, hot, and we're going to measure it by referencing either GND pin with the black DMM probe. The output transformer converts the single ended signal back to differential for transmission to the next signal processor.

We’ll start by setting the controls as follows:

Gain: 2nd Lowest Setting
Output: Fully CW (no attenuation)
Push Switches: All OFF

Using your analog signal generator or DAW input a 1KHz sine signal into your pre. Adjust your signal generator output so your DMM reads 0.200 VAC across the edge card input pins labeled in the diagram below. This is roughly -8 to -15 dBu depending on the input transformer type and source load. Once your input level is established, work your way through the unit. Input signal level is not critical. You just need a signal strong enough to measure and a signal low enough not to clip. You'll note gain increases after the input tx, through the op-amp, and sometimes after the output tx depending on the ratio.

Measure AC voltage between the two points labeled for each test point.

Signal Trace Test Point PDF Download

GOLD

Copper

Bronze

Possible issues with bad voltages at test points:

• Unable to establish voltage at TP1 would indicate you're not sending a signal or signal shorting to ground. Try de-soldering input tx wires black and brown and see if you can establish a signal. If you can, you may have a bad input tx and should contact us.
• TP2 indicates an issue with your relay circuit.
• TP3 indicates an issue with your pad circuit/switch.
• TP4 indicated an issue with your polarity switch.
• TP5 is directly connected to TP4 so an issue here would be poor soldering at the input tx or a damaged trace/pad at either the input tx or polarity switch.
• TP6/TP7 is a likely issue in the box labeled "INPUT" next to the op-amp. Check component values and soldering and confirm "shorts" and "omits" are correct. Possible issue with input tx.
• TP8 is a likely issue in the box labeled "OUTPUT" in the middle of the PCB. Check component values and soldering and confirm "shorts" and "omits" are correct. Possible issue with op-amp or gain switch. Try a different op-amp if possible. Check gain switch testing below and confirm soldering and values of C504, C505, R504, R505, and R506. 
• TP9 would indicate an issue with R506, C506, or output pot soldering. Also confirm value soldering at R600.
• TP10 would indicate a possible issue with C601, output pot soldering, or components in the box labeled "OUTPUT". Confirm all soldering, placement, and polarity.
• TP11 would indicate an issue with R606 value or missing. Possible output transformer wiring issue.
• TP12 possible issue with components in box labeled "TERM" or output tx wiring.
• TP13 is directly connected to TP12 so an issue would be a damaged trace or pad at output tx secondary.

Testing the Gain Switch

These resistors are in series so they can be tested with the unit unpowered and out of your rack. Set your pre gain switch to the max gain setting. Start by setting your DMM to measure DC resistance and measure between the two outside pins (each side of the middle pin) of the Grayhill to main PCB 3-pin connector.

The resistors add up in a ladder as you move from max gain to min gain. Working your way through the ladder will isolate a problem resistor, solder joint, or trace.

* The higher resistor values may take a minute to climb up on your DMM as the resistor ladder gets longer.