Siemens TP-1500 Comfort HMI "No Bootable Device, Please Restart System" – Field Troubleshooting and Repair Reference

1. Problem Summary

A Siemens SIMATIC TP1500 Comfort Panel stops booting and reports the on-screen message "No bootable device, please restart system." The display periodically goes blank, attempts a one-second POST, and then returns to the same error screen. Both power-cycling the HMI and rebooting the connected PLC are ineffective. The fault is non-recoverable from the operator side, persists across cold starts, and is reproducible on every power-on event.

This symptom pattern is well-documented across the SIMATIC HMI Comfort line (TP700 / TP900 / TP1200 / TP1500 / TP1900 / TP2200 Comfort) and on the related KP / KTP Comfort variants. In essentially all field cases, the message indicates a boot medium failure, not a software or configuration issue.

2. Affected Hardware

The TP1500 Comfort is identified by Siemens MLFB 6AV2 124-1MC01-0AX0 (15" widescreen TFT, 1366 × 768, 16 M colors, Touch). Variants include the Basic, Standard, and F-variant (fail-safe) versions. The same NAND-on-BGA architecture is shared across the entire Comfort family:

All Comfort panels use a soldered eMMC / NAND flash BGA chip directly on the mainboard as their only boot medium. There is no user-replaceable SD card or CFast slot acting as the system drive. This architectural decision is the central reason the failure mode is unrecoverable at the field level.

3. Root Cause Analysis

3.1 Boot medium topology

The Comfort panel bootloader scans the mainboard for an enumerated mass-storage device. The onboard NAND chip is presented by the chipset as a USB-style or SATA-style mass-storage endpoint. If the chip:

1. fails to respond on the BGA balls (cold / fractured joints);
2. returns an invalid CSD register or zero-capacity descriptor;
3. has internally lost its controller (wear-out of the NAND array); or
4. has corrupted boot blocks that no longer include a valid partition table or boot signature,

the firmware reports "No bootable device, please restart system." A built-in watchdog then forces a reboot attempt, producing the periodic one-second POST and the recurring loop the operator sees.

3.2 Failure mechanisms

Field-typical failure mechanisms, in order of probability:

1. BGA solder-joint fatigue – thermal cycling of the panel (especially cabinet-mounted panels with high internal enclosure temperatures) fractures the solder balls under the NAND BGA. This is the most common cause in panels older than 5–7 years.
2. NAND wear-out – the eMMC/NAND write endurance is consumed by repeated project downloads, log buffer flushes, recipe storage, and Windows CE registry writes. Panels with high write activity (alarms, data logging) reach end-of-life earlier.
3. Controller / firmware corruption – a brown-out, power loss during a firmware update, or ESD event can leave the chip in an enumerated but unreadable state.
4. Component-level defect – rare, but documented on early production batches; the chip itself fails electrically.

3.3 Why typical software remedies fail

When the bootloader cannot enumerate the device, the panel cannot reach the point at which it accepts a USB stick, executes simatic_hmi_loader.exe, accepts a TIA Portal download, or runs a factory reset. Operations that require the boot medium to be alive are physically impossible to invoke. This is why repeated OS-update attempts, factory-reset sequences, and PLC-driven reboots do not change the symptom.

4. Preliminary Diagnostic Steps

Before concluding the fault is a hardware-level NAND failure, run through this field checklist. Each step takes less than 60 seconds and either rules out or confirms a hardware failure.

1. Verify supply voltage. Measure 24 V DC at the panel's power terminals. Acceptable range per Siemens datasheet is 19.2–28.8 V DC. Under-voltage during inrush can mimic boot failure.
2. Check the status LEDs. The TP1500 Comfort has a power LED and a communication/activity LED on the rear. A solid power LED with a non-blinking activity LED during the POST confirms the bootloader cannot enumerate the NAND.
3. Listen/feel for activity. Absence of any click from an internal buzzer (the panel beeps once on healthy POST) is a strong indicator the bootloader aborted before media enumeration.
4. Try a known-good USB service stick prepared with a current WinCC Comfort image (see Section 5). If the bootloader does not see the USB stick either, the fault is the bootloader/NAND chain, not the project.
5. Discharge the device. Power off, wait 60 s, disconnect all fieldbus and PROFINET cables, then power on again. This rules out bus-induced reset events.

5. Recovery Procedures That Do Not Work

Engineers typically attempt the following before recognizing the hardware nature of the fault. Documenting them explicitly saves time on a service call:

6. Data Backup and Project Recovery

The single most important step before the panel reaches this state is to maintain an external backup. After the fault occurs, project recovery options are limited to the chip-off path described in Section 7.

6.1 ProSave backup procedure (preventive)

1. Connect the TP1500 to the engineering station via PROFINET (or point-to-point with a cross-over cable).
2. Open ProSave (Start → Siemens Automation → ProSave) or the TIA Portal "Backup" dialog.
3. Select Panel → Backup, choose Complete backup with recipes / passwords / users, target a local ".psb" file.
4. Run the backup. Typical duration: 3–8 minutes for a Comfort panel with full project.

6.2 Scheduled backups

Configure the panel's own scheduler to Back up runtime data to external storage weekly, on a USB stick on the rear port. This protects against recipe / log loss even if the boot medium fails entirely.

7. Hardware-Level Repair Options

When the diagnostic flow in Section 4 confirms the NAND cannot be enumerated, three repair paths are available. Choose based on project value, panel age, and downtime tolerance.

7.1 RMA to Siemens Industry Online Support / Repair Center

Siemens operates a paid repair service through its regional Industry Solutions centers. The procedure is:

1. Open a support request at Siemens Industry Online Support with the panel's MLFB, serial number, and firmware version.
2. Request an RMA number (return-material authorization). Provide a fault description: "no bootable device, please restart system".
3. Siemens ships a pre-paid logistics label (where available) for transport to the repair center.
4. The repair typically includes mainboard exchange. The original mainboard is replaced with a refurbished or new unit, and the front bezel / display / backlight are retained.
5. Standard turnaround: 5–10 working days plus transit. Expedited service is available for an additional fee.

After repair, the panel returns with a fresh OS but without the user's project; the latest ProSave backup must be reloaded. The original license is normally transferred by Siemens if the ALM is supplied; otherwise a new license is required.

7.2 Mainboard replacement (in-house or by a Siemens Solution Partner)

For plants with stock of spare Comfort panels, the fastest recovery is to swap the mainboard from a donor unit of the same MLFB. Procedure:

1. Power down and de-energize. Wait 5 minutes for capacitors to discharge.
2. Remove the panel from the cabinet cutout (TP1500 uses integrated tension jacks at the corners).
3. Open the rear service cover (typically 4–6 Torx T10 screws). Note the ground-strap and antenna routing for the Wi-Fi module if present.
4. Disconnect the LVDS flex cable, backlight power, and the touch-panel FPC. Document the connector orientation.
5. Transfer any SD-card-based option modules (slot on the mainboard) to the donor board.
6. Replace the mainboard, re-assemble in reverse order, and reload the project via TIA Portal or ProSave from the most recent backup.

7.3 BGA rework / chip replacement (specialist only)

Some third-party electronics-repair specialists can reball and reflow the BGA NAND, or replace the chip with a pre-programmed replacement. This is cost-effective on older panels and is the only path that preserves any data still resident on the chip. The risk is that prolonged exposure to the rework profile can destroy any remaining blocks, so do not delay the decision.

8. Spare-Parts and Stocking Strategy

For plants running multiple Comfort panels, a structured spare-parts strategy reduces the financial impact of a single fault:

9. Environmental Factors That Accelerate the Fault

Operators frequently ask why a panel fails while a sibling unit, identical firmware, identical project, does not. The dominant variables are environmental and electrical:

• Cabinet internal temperature. Comfort panels are rated 0–50 °C operating, with the BGA joint lifetime halved for every 10 °C above 30 °C. Panels in non-climate-controlled cabinets near VFDs, servo drives, or transformer coils fail first.
• Thermal cycling. Panels that are powered down overnight see 20–30 K swings; BGA solder fatigues faster than in continuously-running panels.
• Vibration. Panels mounted on press lines or stamping equipment see mechanical stress on the BGA. Use the rear mounting clamps with rubber isolators.
• Power-quality events. Surges, sags, and DC bus droops on the 24 V rail during weld-gun firing or motor inrush. A Phoenix Contact QUINT or Siemens SITOP smart power supply with diagnostic output is recommended.
• Write activity. Panels configured with verbose data logging to internal storage (>10 MB/day), recipe cycling, or alarm logging with persistence exhaust the NAND more quickly.

10. Re-Commissioning After Repair

After a mainboard swap or RMA return, follow this verification sequence before returning the line to production:

1. Apply 24 V. Confirm the panel POSTs and displays the Windows CE / WinCC RT loader screen within 30 s.
2. Set the panel's IP address, subnet mask, and gateway to the production network values. Verify the device name matches the PROFINET configuration (STEP 7 / TIA Portal device name assignment).
3. Connect the engineering station, run ProSave → Restore, and transfer the latest ".psb" backup.
4. Verify license activation via the Automation License Manager. Panel-internal licenses on the original mainboard do not transfer to a replacement mainboard; licenses on a USB stick or transferred to the new mainboard's CFast are required.
5. Run a project consistency check from TIA Portal (Online → Compile and check consistency) against the live panel.
6. Force an alarm test to confirm operator-input and message-display paths work end-to-end.
7. Update the maintenance record: panel serial number, MLFB, firmware, project version, and license key.

11. Related Comfort Panel Failures

The same NAND-on-BGA architecture means similar symptoms appear across the family. Cross-reference is useful for field service teams supporting a fleet:

12. Quick Reference Flowchart

The decision path summarized visually:

13. Frequently Asked Questions