Description
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Pacific Scientific |
| Model | 6420-001-N-N |
| Series | 6410 Stepper Drives |
| Drive Type | Microstepping indexer drive |
| Input Voltage | 24–75 VDC |
| Maximum Output Phase Current | 5 A RMS |
| Peak Current | 7.1 A peak |
| Fixed Binary Resolution | 200–51,200 steps/revolution |
| Fixed Decimal Resolution | 200–50,000 steps/revolution |
| Variable Microstepping | 20,000 steps/revolution at 0.02–5,700 RPM |
| Serial Interfaces | RS-232, RS-422, RS-485 |
| Programmable I/O | 8 bidirectional I/O ports |
| Internal Memory | 1,792 bytes NVRAM |
| Operating Temperature | 0–50°C |
| Maximum Chassis Temperature | 60°C |
| Humidity | 10–90%, non-condensing |
| Fault Protection | Line-to-line/line-to-neutral shorts, under/overvoltage |
The published data specifies convection cooling or optional heatsinking for the 5 A full-current rating at 25°C. The discrete outputs are open-collector devices rated at 30 VDC and 70 mA sink, while discrete inputs accept up to 30 VDC.
Field Application & The “Trench” Experience
A common legacy-machine scenario would be a packaging or material-handling system in which the 6420 is doing more than simply energizing a stepper motor. The controller may have stored indexing sequences, I/O assignments, and motor-resolution parameters inside the drive. When the unit fails, replacing it with a generic stepper amplifier can restore motor rotation but leave the machine’s indexing logic unavailable.
The practical replacement sequence is therefore to document the existing 6420 program, communication setup, motor-current settings, and I/O assignments before removing the failed unit. Once the replacement is installed, the maintenance engineer can validate the motion sequence rather than testing only whether the motor spins.
Niche applications include:
- Packaging-film registration axes — repeatable indexing of film, labels, or web material.
- Cut-to-length mechanisms — programmed stepper positioning where the indexer handles motion sequences locally.
- Automated inspection fixtures — controlled rotary or linear positioning synchronized with discrete sensors.
- Legacy material-feed equipment — two-axis stepper positioning where replacing the original controller would require PLC software changes.
The 6420 documentation specifically describes programmable I/O, serial communication, master-slave operation, and the ability to control two synchronous or independent axes.
6420-001-N-N
6420-001-N-N
QA & Testing
For new-surplus or refurbished 6420-001-N-N inventory, the inspection should address the indexer electronics as well as the power stage.
Incoming inspection
- Confirm the complete
6420-001-N-Nidentification. - Check terminal blocks, connectors, PCB surfaces, mounting hardware, and enclosure condition.
- Look for corrosion, cracked components, overheated areas, or evidence of unauthorized modification.
Electrical testing
- Apply controlled 24–75 VDC input power.
- Verify startup behavior and fault protection.
- Test the serial communication interface where applicable.
- Verify discrete input and output operation.
Motion testing
- Connect an appropriate stepper motor/test load.
- Verify phase-current regulation.
- Test multiple microstep resolutions.
- Execute representative indexing commands.
- Confirm repeatable start/stop and direction behavior.
The drive is listed in the secondary market as a discontinued product, with current availability generally handled through surplus, unused stock, refurbished units, or repair services rather than standard factory-new production.
Veteran’s Tech Trap Guide
⚠️ Trap #1 — Confusing the indexer with a conventional stepper amplifier.
The 6420-001-N-N contains motion-indexing functionality. If the original machine relies on programs stored in the drive, a simple replacement amplifier will not reproduce that behavior.
PRO TIP: Before removing the old unit, record the existing program, serial communication parameters, microstep settings, current settings, and I/O assignments.
⚠️ Trap #2 — Forgetting the NVRAM.
Published specifications identify approximately 1,792 bytes of NVRAM for user programs. If the failed drive can still communicate, retrieve the application data before declaring it unusable.
⚠️ Trap #3 — Assuming 5 A RMS means unrestricted 5 A operation.
The published 5 A rating is tied to thermal conditions. Convection cooling or an appropriate heatsink may be required for the full rating at 25°C. Cabinet temperature and mounting conditions therefore matter during commissioning.
Dynamic FAQ
What is the Pacific Scientific 6420-001-N-N?
It is a microstepping indexer drive module from Pacific Scientific’s 6410 Stepper Drives family. It combines programmable motion indexing with stepper-motor drive electronics.
What is its DC input range?
The specified input range is 24–75 VDC. Maximum motor phase current is listed as 5 A RMS, with 7.1 A peak for microstepping operation.
Does the 6420-001-N-N communicate through a serial port?
Yes. Published specifications identify RS-232, RS-422, and RS-485 serial interfaces.
How much program memory does it have?
The unit has approximately 1,792 bytes of NVRAM for user programs. The published documentation also identifies a menu-driven software package called 6420 Dialogue.
Is the 6420-001-N-N discontinued?
Radwell identifies the part as discontinued by the manufacturer, while secondary suppliers continue to list unused, surplus, refurbished, and repair options.
How should I verify a New Surplus 6420-001-N-N?
Request photographs of the actual unit showing the complete part number, not merely a stock photograph. For a critical replacement, also request functional-test documentation covering DC input, motor output, serial communication, I/O, and indexing operation. “New Surplus” should mean unused inventory; it should not be treated as equivalent to current factory production.
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