Dental X-ray systems

Midmark Preva: troubleshooting and error codes

The ServiceForge knowledge base holds 23 documented symptoms for the Midmark Preva, with 53 ranked causes, 80 diagnostic checks with test points and expected values, and 2 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Power is ON but no operator display high voltage

System powered on but operator panel displays no information, may have buzzing sound

Ranked causes

1. No AC mains power to USB hub (common)
2. Service disconnect switch failure (occasional)
3. Communication cable between Logic Board and Operator Panel damaged (occasional)
4. Ribbon cable between Power Supply and Logic Board loose or damaged (occasional)
5. Logic Board voltage supply failure (occasional)
6. Power Supply Board failure (occasional)
7. Logic Board failure (occasional)
8. Operator Panel Board failure (occasional)

First check

Check for 100-230V AC at Power Supply Board J4 USB Hub Power connector

Expected: 100-230 volts AC present
Tools: Multimeter

10 more checks with pass and fail actions, 8 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

No kV produced high voltage

Operator panel displays message that kV is too low; no high voltage produced during exposure

Ranked causes

1. D11 light on Power Board not illuminated (common)
2. Power Supply Board output voltage out of range (common)
3. Logic Board missing supply voltages (common)
4. Power Supply Board missing supply voltages (common)
5. Logic Board kV Setpoint voltage incorrect (occasional)
6. Ribbon cable between boards damaged or unseated (occasional)
7. Cable between Control Unit and Tube Head assembly damaged (occasional)

First check

Verify D11 indicator lamp illumination

Test point: D11 on Power Board
Expected: D11 light illuminated

5 more checks with pass and fail actions, 7 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

High-voltage breakdown during exposure high voltage

Loud snap sound occurs during exposure attempt. High voltage present but excessive and uncontrolled.

Ranked causes

1. Circuit breaker tripped during exposure (common)
2. Power Board failure (occasional)
3. Power Supply Board voltage out of range (occasional)
4. Faulty cabling between boards or to tube head (occasional)
5. Tube Head Assembly malfunction or feedback circuit failure (occasional)
6. Logic Board failure (occasional)

First check

Verify D11 indicator light status on Power Board

Test point: D11 light on Power Board
Expected: illuminated

4 more checks with pass and fail actions, 6 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Device ready but no radiation produced radiation

System powers on, Ready indicator illuminated green, exposure switch activated, but no X-ray output; relay and LED may or may not engage; audible indicators may not sound

Ranked causes

1. Operator Panel indicator does not sound upon exposure (common)
2. Relay or D2 LED do not activate on Power Board (occasional)
3. D401 on Logic Board does not illuminate during exposure (occasional)
4. Exposure signal conductor in Cat 5 cable is open (occasional)
5. Logic Board indicator sounds but Power Board does not activate (rare)

First check

Verify system power and Ready indicator

Test point: Operator Panel Ready Indicator LED
Expected: Green light illuminated when Preva is powered on and idle

5 more checks with pass and fail actions, 5 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Electrical integrity inspection high voltage

Verify integrity of power cord, circuit breaker, power switch, X-ray irradiation switches, and operator panel functionality.

Ranked causes

1. Power cord damage or loose ground connection (unknown)
2. Circuit breaker or power switch malfunction (unknown)
3. Exposure switch malfunction (unknown)
4. Operator panel malfunction or display issue (unknown)

First check

Visually inspect power cord for damage

Test point: Power cord
Expected: No cuts, breaks, or damage visible

5 more checks with pass and fail actions, 4 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Continuous beep at power-up

Continuous beeping sound during power-up; display may be backlit or normal

Ranked causes

1. Operator Display Board fault with missing or incorrect technique factors display (common)
2. Logic Board fault with missing or incorrect technique factors display (common)
3. Logic Board fault with normal display (occasional)

First check

Inspect display condition at power-up

Test point: Display screen
Expected: Display backlit with technique factors visible, or display with normal operation

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error – Serial Communication displays

Error message displayed indicating no communication between Logic Board and Operator Panel

Ranked causes

1. Cat 5 communication cable open between Logic Board and Operator Panel (common)
2. Logic Board or Operator Panel Board fault (occasional)

First check

Inspect Cat 5 communication cable continuity and condition

Test point: Cat 5 cable between Logic Board and Operator Panel
Expected: Cable intact, properly connected, no breaks or open circuits

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

No display or abnormal display at power-up

Operator Display Board is backlit but does not show technique factors, or no display appears at all

Ranked causes

1. Operator Display Board failure (common)
2. Logic Board failure (common)

First check

Verify display backlight status

Test point: Operator Display
Expected: Display backlit

2 corrective actions and part numbers are in ServiceForge. Connect ServiceForge to your AI

No X-ray produced but exposure indicators detected radiation

Unit operates exposure indicators but produces no X-ray output. Diagnostic mode shows either no kV or no mA produced.

Ranked causes

1. No kV produced (unknown)
2. No mA produced (unknown)

First check

Activate Diagnostic Mode

Test point: Operator Panel
Expected: Diagnostic Mode active per page 192 procedure

1 more check with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Buzzing Noise at Power-Up

System produces buzzing sound during power-up sequence

Ranked causes

1. Ribbon cable between Power Supply Board and Logic Board not properly seated or damaged (common)

First check

Inspect and reseat ribbon cable between Power Supply Board and Logic Board

Test point: Ribbon cable connection
Expected: Cable fully seated with no gaps

1 more check with pass and fail actions, 3 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Articulated Arm balance and friction caution

Articulated Arm balance or friction out of specification; arm not steady in all positions or does not move smoothly

Ranked causes

1. Balance or friction adjustment required (occasional)

First check

Verify Articulated Arm is steady in all positions when Tube head is moved

Test point: Articulated Arm assembly
Expected: Arm remains steady in all positions and moves before Horizontal Arm

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Caster tightening (Mobile units only) patient safety

Inspect and tighten loose caster bolts on mobile base to prevent system wobbling and unsafe operation.

Ranked causes

1. Loose caster bolts from repeated rolling over rough surfaces (common)

First check

Visually inspect casters for visible looseness

Test point: Caster attachment to mobile base
Expected: Caster snug against base, no visible threads between caster and base

3 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Device support inspection patient safety

Verify structural integrity of wall attachment and ensure Preva system is securely fastened to the wall.

Ranked causes

1. Inadequate wall support or loose attachment (unknown)

First check

Visually inspect wall support adequacy

Test point: Wall support structure
Expected: Wall support adequate and secure

1 more check with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Horizontal Arm brake adjustment caution

Horizontal Arm does not move with proper resistance; should begin to move after Articulated Arm

Ranked causes

1. Brake assembly screws not properly tightened (common)

First check

Verify Horizontal Arm moves after Articulated Arm when Tube head is repositioned

Test point: Horizontal Arm pivot post
Expected: Horizontal Arm begins to move after Articulated Arm; Articulated Arm steady in all positions

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Horizontal Arm pivot braking

Adjust brake assembly screws to ensure Horizontal Arm begins to move only after Articulated Arm

Ranked causes

1. Factory pre-set braking requires verification during installation (unknown)

First check

Verify Articulated Arm movement before Horizontal Arm

Test point: Brake assembly clamping bar at Control Unit top
Expected: Articulated Arm moves before Horizontal Arm begins to move; Tube head remains steady in all positions

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Imaging performance verification radiation

Verify that Preva produces acceptable radiographic images of a test object as intended.

Ranked causes

1. Imaging system malfunction or degradation (unknown)

First check

Acquire radiograph of test object

Test point: Test object radiograph
Expected: Image quality acceptable for clinical use

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Irradiation interlocks operation verification radiation

Verify that irradiation interlock circuits safely inhibit X-ray operation when safety switches open (e.g., door open), and that X-ray resumes when interlock is closed.

Ranked causes

1. Interlock circuit malfunction or damage (unknown)

First check

Visually inspect irradiation interlock circuit and exposed wiring

Test point: Interlock circuit and related wiring
Expected: No damage visible

5 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: kilovoltage (kV) radiation

kV output does not match desired technique factor setting; requires X-ray kV meter (Radcal Accugold or similar) to verify and adjust output

Ranked causes

1. kV output requires adjustment to match set technique factor (unknown)

First check

Enable Diagnostic Mode

Test point: System menu
Expected: Diagnostic Mode active; operational display returned

7 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: Mechanical integrity inspection patient safety

Verify mechanical integrity of Control Unit, Horizontal Arm, Articulated Arm, Yoke, Tube Head, and attachment points are structurally sound without excessive wear or wobbling.

Ranked causes

1. Mechanical wear, damage, or loose connections (unknown)

First check

Visually inspect Control Unit

Test point: Control Unit
Expected: No visible damage, excessive wear, or looseness

5 more checks with pass and fail actions, 1 corrective action, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: On-machine labels inspection patient safety

Verify legibility of all device on-machine labels that communicate important safety messages.

Ranked causes

1. Labels illegible, damaged, or missing (unknown)

First check

Visually inspect all on-machine labels for legibility

Test point: All on-machine labels
Expected: All labels clearly legible

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Calibration: X-ray performance QA by Qualified Physicist radiation

Arrange for X-ray performance inspection by a Qualified Physicist to verify essential X-ray functionality.

Ranked causes

1. X-ray performance degradation or non-compliance (unknown)

First check

Arrange and complete X-ray performance QA by Qualified Physicist

Test point: X-ray system performance
Expected: Performance meets specification per Qualification Procedure

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Pre-Termination Error displays without cause high voltage

Error screen appears when exposure button is released early or from high-voltage breakdown in tube head; system normally returns to normal operation after five seconds

Ranked causes

1. Exposure button released early during exposure cycle (common)

First check

Verify operator exposure button release timing

Test point: Operator technique
Expected: Button held for full exposure duration per technique selection

3 more checks with pass and fail actions, 2 corrective actions, and part numbers are in ServiceForge. Connect ServiceForge to your AI

Ribbon cable defect between Power Supply and Logic Boards caution

Faulty ribbon cable connection between Power Supply and Logic Boards causing system malfunction.

Ranked causes

1. Ribbon cable damaged or disconnected (unknown)

First check

Inspect ribbon cable between Power Supply and Logic Boards

Test point: Ribbon cable connector
Expected: Cable intact, fully seated, no visible damage

1 corrective action and part numbers are in ServiceForge. Connect ServiceForge to your AI

Error codes

Code	Meaning	Trigger	Severity
`Error – Serial Communication`	No communication between Logic Board and Operator Panel	Cat 5 cable open or Logic Board/Operator Panel Board failure	error
`Pre-Termination Error`	Exposure terminated prematurely resulting in underexposed image	Early release of exposure button or high-voltage breakdown in Tube Head	warning

Likely causes and actions for each code are in ServiceForge. Connect ServiceForge to your AI

Community

0 fixes logged by technicians through their AI, with outcomes, for this model.

ServiceForge knowledge base record. Field-unverified unless technicians confirmed it. A teaching summary of the record, not a service manual. Export 2026-10-14.