MS720 Dual Load-Cell Troubleshooting, Hold Modes & RS-232 Guide

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For replacement or troubleshooting help, call MNM Scales at (832) 290-3120 or email mnmscales@yahoo.com.

MS720 Dual Load-Cell Troubleshooting, Hold Modes & RS-232 Guide

Symptom: only one pallet beam changes the display

Test each beam with a modest load while watching the display. Inspect the non-responsive beam cable and connector, then the corresponding MS720 input. Do not repeatedly connect/disconnect energized equipment unless the manufacturer permits it. A dead side can be the load bar, cable, connector or input—not automatically the indicator.

Symptom: weight is unstable or changes when cable moves

Inspect cable jackets, strain relief and connector pins. Movement-sensitive readings often point to an intermittent conductor or connector. Also verify the beams sit flat and do not rock. Recharge or use stable AC power to rule out power problems.

Symptom: weight freezes or seems slow

The MS720 listing includes multiple Hold functions and animal weighing. A frozen-looking value can be normal if a Hold mode is active. Return to ordinary weighing and test again before changing calibration. Auto-hold/animal modes intentionally stabilize changing loads differently from continuous weighing.

RS-232 printer or remote display will not communicate

MNM lists full-duplex RS-232, but successful communication requires matched baud rate, data bits/parity/stop settings where applicable, cable pinout and output/print mode. Verify communication parameters on both devices. Do not assume a cable is correct because both connectors fit.

How to decide indicator vs load-bar failure

If both bars behave identically wrong, the indicator configuration, common power/excitation or calibration is more suspect. If one bar alone behaves differently, focus on that bar/cable/input. If available, use controlled connector swapping only when the connector/pinout is known to be identical and the equipment is powered down. Document the result so parts are not replaced by guesswork.

After any repair

Check unloaded zero, verify both beams respond, run known-load span calibration if configuration or sensing hardware changed, and test repeatability plus different positions. A portable pallet-beam scale should also be checked after relocation or impact.

Main guide: https://www.allscalesusa.com/post/mnm-ms720-dual-connector-pallet-beam-indicator-guide Compatibility: https://www.allscalesusa.com/post/ms720-dual-op-919-replacement-indicator-compatibility MNM product: https://mnmscales.com/product/myscale-ms720-lcd-indicator-with-dual-connectors-for-pallet-beam-scale-load-bars/