PCB reference
ZX7-315 / 400 / 500 / 630 PCB Test Points and Adjustment Reference
Board-level test-point table for large ZX7 IGBT inverter welders, including TP1-TP16 values, +15V, -15V, +5V rails and current calibration points.
Why the test-point table matters
Large ZX7 IGBT inverter welders can show similar external symptoms while failing in different sections. A test-point table gives the technician a way to stop guessing. Instead of replacing PCB1, PCB2 or the IGBT module blindly, the repairer can check whether the control board has its expected internal references, current-command levels, feedback levels and positive/negative supply rails.
The service data lists TP1 through TP16 for ZX7-315, ZX7-400, ZX7-500 and ZX7-630. Some values are common across the series, while others change with the current rating. These values should be treated as a board-level reference for the same control-board family, not as a universal value for every unrelated ZX7 clone.
PCB test-point voltage reference
| Test point | Reference value | Diagnostic meaning |
|---|---|---|
| TP1 | -3.63V | Low-voltage control reference. Abnormal value suggests reference or supply trouble. |
| TP2 | 2.5V | Reference level used by the control loop. |
| TP3 | ZX7-315: -0.2 to -3.2V; ZX7-400: -0.2 to -4V; ZX7-500: -0.2 to -5V; ZX7-630: -0.2 to -6.3V | Rating-dependent control range. |
| TP4 | ZX7-315/400: 4.05V; ZX7-500: 5V; ZX7-630: 6.3V | Maximum clamp-current adjustment reference. |
| TP5 | 0.015V | Low-level feedback/reference point. |
| TP6 | 3V | Control-board reference voltage. |
| TP7 | Waveform point | Should be checked with suitable oscilloscope and isolation practice. |
| TP8 | 1.1V | Control signal reference. |
| TP9 | 2.89V | Control signal reference. |
| TP10 | Long: 2.18V; Short: 1.69V | Mode-dependent voltage related to output cable setting. |
| TP11 | Long: 2.08V; Short: 1.48V | Second mode-dependent voltage related to cable setting. |
| TP12 | +15V | Positive control supply rail. |
| TP13 | -15V | Negative control supply rail. |
| TP14 | +5V | Logic/control supply rail. |
| TP15 | -0.4V | Minimum current adjustment check point. |
| TP16 | ZX7-315: -6.3V; ZX7-400: -8V; ZX7-500: -10V; ZX7-630: -12.6V | Maximum current adjustment check point. |
Current adjustment procedure
The service procedure uses shorting jumpers matched to the welder rated current. After the correct jumper is selected, minimum current is checked at TP15 and adjusted with 1VR5. Maximum current is checked at TP16 and adjusted with 1VR4. Maximum clamp current is checked at TP4 and adjusted with 1VR3. This means that a current-control complaint should not be closed until the board has been adjusted against the correct current-rating jumper.
| Adjustment | Measure at | Trim part | Use case |
|---|---|---|---|
| Minimum current | TP15 | 1VR5 | When low-current range is wrong or arc cannot be reduced properly. |
| Maximum current | TP16 | 1VR4 | When output cannot reach rated current or current command is too high. |
| Maximum clamp current | TP4 | 1VR3 | When the control loop needs current limiting calibration. |
How to use the table without damaging the board
- Confirm the exact board family and current rating before using the values.
- Use the correct meter reference and avoid slipping probes across adjacent pins.
- Check TP12, TP13 and TP14 early because +15V, -15V and +5V rails support much of the control logic.
- Do not adjust trimmers randomly. Record the original position before calibration.
- After adjustment, confirm welding output behavior under safe load conditions.
Interpreting the supply rails
TP12, TP13 and TP14 are especially useful because they represent the +15V, -15V and +5V rails. Many control-board symptoms become easier to classify once these three rails are known. If +5V is missing, logic and display behavior can become unreliable. If either ±15V rail is missing, analog feedback, comparator and operational-amplifier sections may fail even though some lamps still work.
When these rails are wrong, do not adjust current trimmers first. Fix supply integrity before calibration. A board calibrated with unstable rails will not remain correct after the supply fault is repaired.
Using rating-dependent values
TP3, TP4 and TP16 change with the machine rating. That is expected. A ZX7-315 board and a ZX7-630 board should not be forced to the same maximum-current voltage. Use the current-rating jumper and the correct value for the actual machine. This is one reason a generic “ZX7 board” replacement can behave incorrectly when installed into a different current class.
Before changing trimmers, photograph the original positions and record measured values. If the machine becomes worse after adjustment, the record gives a way back. Good repair documentation is especially important on older OEM machines where exact board revisions are not always marked clearly.