Bond the screen and its enclosure to ground as two separate connections and feed the panel from a dedicated supply with battery backup within 25 feet of the screen, then retest the power-up and the keypad sequence. Field reports on 12 and 15 inch panels span firmware versions, and 6 inch panels in the same fleet stayed clean, so the electrical fix comes first and firmware second.
White screens and lockups on 12 and 15 inch HMI panels are an installation fault in the field reports that matter here, and the fix that held for years is electrical. Bond the screen and its enclosure to ground as two separate connections, and feed the panel from a dedicated supply with battery backup mounted at the screen, not in a cabinet down the wall. Then reproduce the power-up and the keypad sequence that faulted. The reports name firmware 2.77, but the same panel sizes white-screened across firmware versions, and 6 inch panels in the same fleet stayed clean. A power reset recovers the panel, and the fault returns until its condition is removed. Work the checks in this order: supply at the panel terminals, the two ground bonds, the keypad trigger, the memory card.
What each symptom points to
Five observations from the reports, and each narrows the search:
- White screen at power-up, at times with "no user program" across it. The fault sits in the startup path. Measure the supply at the panel terminals during power-up and write down the exact message.
- Lockup while a numeric entry object's keypad is open. A runtime trigger. Reproduce that same entry under observation with the wiring untouched.
- A power reset restores normal operation. Recovery. Keep the case open until the retest passes on corrected power and grounds.
- Only the 12 and 15 inch panels fault; the 6 inch panels stay clean. About 25 installs of each size back that split. Use size as scope: the fix targets the larger panels, and the split fits a supply and bonding limit that grows with panel load.
- A dedicated supply and oversize wire fitted, faults continue. Distance from supply to screen and the reading at the terminals are what remains. One 12 inch install with both upgrades still white-screened, fed from a supply far from the panel.
A dark screen instead of a white one points elsewhere; a blank, frozen HMI checked against power first is that diagnosis.
Measure the supply at the panel terminals
The number that decides this case is the voltage at the panel's own terminals during the fault condition: through power-up for the startup fault, through the keypad entry for the runtime fault. Compare it against the electrical specification printed for that panel, family by family.
Inspect the terminations first. A loose or corroded lug on the DC feed produces this class of intermittent fault. Then watch the meter through the same conditions that faulted.
One 12 inch installation carried a dedicated supply and oversize wire and still faulted, because the supply sat far from the screen. The placement rule from installs that stayed clean: a dedicated supply with battery backup at the screen, no more than 25 feet of wire between them. Longer runs also pick up more noise, the same class of interference that freezes an HMI on a DC supply shared with solenoid coils, and the measurement method in checking the supply drop behind a dim HMI screen applies to this fault the same way.
Bond the screen and the enclosure as two checks
The remedy that cleared these panels for years grounds two things: the screen and the enclosure it sits in. Verify each connection on its own. A panel chassis grounded only through its mounting brackets can sit unbonded inside a correctly grounded enclosure.
Kill the feed and lock it out before you open the door or touch a ground lug.
Use the panel's documented chassis grounding point for one bond and the enclosure's documented ground for the other. After correcting either one, repeat the power-up or keypad test before you judge the result. Panels that need a periodic power cycle traced back to supply and ground fail on the same two paths, so those checks ride along here.
Reproduce the keypad sequence
A trigger is tested by repeating it. With the panel running normally, open the same numeric entry object, make the same entry, close the keypad. Record which object was active if a fault lands. Hold the project and the electrical setup fixed while you test; changing both at once tells you nothing about either. If the fault appears only in this sequence and the terminal readings sit inside the printed specification, you have a narrow case for the panel vendor: one object, one entry path, one firmware version.
Treat the memory card as one test variable
One faulting 12 inch panel ran with a memory card installed. That is a variable, so change it last, and only when the application tolerates running without it. Back up what the card holds, remove it by the panel's documented procedure, and repeat the startup test.
A white screen carrying "no user program" at power-up has a second path worth its own look, because the panel is reporting it has no project to run: see an HMI panel booting to no user program with a blank card. If the message shows on every start after the power fix, move to project storage, and a panel that loses its project after a power cycle covers that diagnosis.
Example: a 15 inch panel fed from 30 feet
A 15 inch panel on firmware 2.77 white-screens at power-up with "no user program" on it; a reset clears it, and the fault has landed twice in its first week. The supply is a dedicated unit in a floor cabinet 30 feet away.
Apply the placement rule. Thirty feet of wire runs 5 feet past the 25 foot limit (30 − 25 = 5), and the conductor loop out and back is 60 feet (2 × 30). Move the supply, with its battery, into a box 6 feet from the screen: the loop drops to 12 feet (2 × 6), which is 48 feet shorter (60 − 12). While the feed is locked out, bond the panel chassis and the enclosure as two connections.
Retest against the fault's own frequency. Ten power-up cycles and 20 openings of the numeric entry object in one day, then a normal week of production: zero white screens closes it as an installation fix. One white screen on verified terminal voltage sends the case to the vendor with the readings and the sequence attached.
Where firmware fits
The 2.77 reports are real, and so are years of the same white screens on 12 and 15 inch panels across versions, cleared electrically and kept clear. Update firmware on a panel only after its terminal readings sit inside the printed specification and both ground bonds are verified; done earlier, the update changes two variables at once and the next white screen teaches you nothing. A panel that still faults on close, clean power goes to the vendor with the record: size, firmware version, power-up or runtime, keypad open or closed, exact message, card fitted, reset result. A white-screened panel that stops accepting a connection is a repair case, so stop testing and send it in.
The decision
Recommendation: for any 12 or 15 inch HMI panel that white-screens, bond the screen and the enclosure to ground as two separate connections, feed it from a dedicated supply with battery backup within 25 feet of the screen, and retest the exact power-up and keypad sequence before you touch firmware.
- Occasional white screens on a 12 or 15 inch panel: apply the full fix, then retest.
- Fault only with the keypad open, on verified terminal voltage: hand the vendor the object and the entry sequence.
- "No user program" on every power-up after the fix: move to project storage checks.
- 6 inch panels in the same fleet: leave them running; the reports put the fault on the larger sizes.
Questions
Does firmware 2.77 cause the white screens?
The reports name 2.77, but 12 and 15 inch panels white-screened across versions for years, and about 25 six inch installs in the same fleet never faulted. One installer's history had every earlier case clear only with the next firmware release, while the same sizes stayed clean for others after power and ground work. Let your terminal readings pick your path, and ask for the firmware change list before you update.
Why does the supply need to sit within 25 feet of the screen?
It is a field rule from installs that stayed clean, not a printed specification. The short distance gives you a small conductor loop and a battery riding next to the panel through every dip. If a longer run must stay, record the terminal voltage through ten power-up starts first; a reading that holds inside the printed range is your evidence to leave it.
A power reset clears the white screen. Is the panel broken?
A reset only brings the panel back, and the fault returns until its condition is gone. Check the panel's alarm or event history before you stand at the machine: the timestamps separate power-up faults from runtime faults. If it still white-screens on verified power and grounds, or it stops accepting a connection, it is a repair case.
What should I record before calling the panel vendor?
Panel size, firmware version, power-up or runtime occurrence, the exact message on the white screen, whether a numeric entry keypad was open, whether a memory card is fitted, and whether a reset restored operation. Send the project file and panel configuration with it, because support reproduces the fault with those in hand. Attach your terminal voltage readings and the ground checks you made.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.