The Level 2 method for imagers: histories, counters, test prints and density readings

Collect the error history, notifications and counters, use an internal test print and a few density readings to place an imager fault in film, transport, image writing, processing, electronics or the sending host, and know what you may and may not change.

Where Level 1 ends

Level 1 gave you the chain of a dry imager, the safety rules, jam clearing, the step-wedge calibration, DICOM print settings and the PM routine. Lesson 6 of that course gave you a first fault-finding order: complaint, log, counters, film box, test print, then cheap and likely before expensive and rare. Most calls end there. Level 2 is for the ones that do not: the jam that returns three days after a perfect cleaning, the calibration that fails on fresh film, the line that survives a head cleaning, the printer that prints from one console and not from another, the error code that is not in your table at all.

The trap at this level is to believe the subsystem that reported the error. An imager is a chain with many hand-offs, and each block watches its neighbours. The densitometer reports a calibration failure when the film is fogged; the processor reports a warm-up failure when the room is cold or the supply cord is too thin; the controller reports lost communication when a storage card is dying. Replace the block that complained and you have spent the customer's money and kept the fault. The method below is about finding the first cause, proving it with a cheap test, and changing one thing at a time.

Read the history, not just the screen

The front panel shows the current condition. The history shows how the machine got there. Most imagers keep at least an error history with time stamps, and many keep separate logs for the application, the DICOM service, print delivery and the operating system, reachable through a service tool or a web page. The DRYPRO SIGMA service manual, our example machine, describes eight logs and suggests a sensible order: count how often the error occurred in the error history, find its exact time, then read the application log for the events just before it. That order works on almost any brand.

Look for three things. First, the first event in a burst: when a supply dips, you may see a processor error, a transport error and a lost connection within a second, and only the first one points at the cause. Second, the quiet events: many imagers write notifications that never reach the screen, such as pick-up retries, communication retries, a laser power approaching its limit or a densitometer reading drifting towards the end of its range. A rising count of those over weeks is the fault growing. Third, the gaps: a log that suddenly restarts, a clock that jumped back years, settings that have returned to defaults. Those point at power loss, a backup battery, or a storage device and its file system.

Codes on the screen and codes in the log are not always the same number. The example machine shows a short code on the panel and a longer one, with a subsystem prefix, on the web page and in the log. Field cases show other brands doing similar things, and also codes that are simply missing from the documentation you have. When the code is unknown, the subsystem prefix, the time and the events around it are still useful evidence.

• Save or photograph the error history and logs before any restart or reset.
• Note the counters: total prints, prints since the last PM, per-tray counts, filter counters.
• Check the system clock and date; a wrong clock scrambles the order of events.
• Ask what changed: film delivery, power cut, move, new modality, software update, earlier service visit.

Counters and notifications as early warnings

Counters tell you how hard the machine has worked and when it was last looked after. A transport fault on a machine that is far past its PM count is first a PM job. The example manual asks for a PM every 20,000 film cycles and, at an emergency call, switches to the full PM procedure when the count since the last PM is close to that figure; other brands set their own intervals, so use the manufacturer's numbers for the model in front of you. Counters per tray and per film size also tell you whether a fault follows one tray or one size.

Notifications are where Level 2 work is won. On the example machine a pick-up retry, a laser power close to its limit and a densitometer reference reading near the end of its range are each written to the log as a notice while printing continues normally. If you see them, you have found the next breakdown before it happens. Write the counts in your report, compare them on the next visit, and plan the part or the adjustment before the department loses a day.

Split the chain with test prints and density readings

The internal test print is the strongest single test you have, because it is generated inside the imager and never touches the network or the modality. If the internal pattern shows the fault, the cause is inside the printer. If the pattern is clean and only clinical films are wrong, the cause is in the image the sender produces or in the print settings for that sender. Use a flat grey field for lines, bands and uneven density, a step wedge for the tone curve, and a pattern of the SMPTE type for geometry, borders and fine detail.

Inside the printer, split again. Print the same pattern from each tray and on each film size: a fault that follows one tray belongs to its pick-up, its tag reader or its film box; a fault on every tray belongs to the shared path. Print several sheets in a row from a cold start: a fault that appears only after warm-up points at heat, a binding motor or a slipping roller. Look at the sheet against the light and mark which edge came out first, then decide whether the artefact runs along or across the direction of travel, as Level 1 lesson 4 taught.

Measure, do not guess. A hand-held transmission densitometer, itself checked against a reference strip, turns 'it looks grey' into numbers you can compare: base plus fog on an unexposed area, a mid-grey step, the darkest step, and the same patch at the left, centre and right of the sheet. A high base plus fog on every film points at the film or the processor temperature. A low maximum density with a normal base points at the processor, the laser power or the head energy. A difference between left and right points at the processor contact, the head or the optics. These readings take five minutes and they decide which assembly you open.

Six places a fault can live

With the history, the counters, the test print and a few readings, place the fault in one of six areas before you take a cover off. Each area has its own lesson in this course.

Keep in mind that a fault can sit in one area and show in another. A sheet of film welded to the drum spoils every later calibration; a glazed roller makes the sheet late at a sensor and looks like a sensor fault; a thin supply cord makes the heater slow and looks like a processor fault. When your first area does not explain everything you see, check the neighbour.

• Film and consumables: type, side, batch, age, storage, tag or backing sheet, counterfeit or wrong-region stock (lessons 5 and 8).
• Supply and transport: pick-up, vacuum, rollers, springs, guides, sensors, motors, jam areas (lesson 2).
• Image writing: thermal head and platen, or laser, optics and polygon (lessons 3 and 4).
• Processing and density control: drum or plate, heaters, temperature sensors, densitometer, calibration data (lessons 4 and 5).
• Electronics: power supply, fans, interlocks, controller, storage, firmware (lesson 6).
• Host and network: DICOM settings, LUTs, film sizes, queues, addresses, routers (lesson 7).

Swap, isolate, measure — and what you may change

Swap tests are powerful on imagers because so many have pairs: two trays, two pick-up modules, two film boxes, two identical printers in one department. Swap one thing, test, and put it back if nothing changed. Isolation is the second tool: print from a laptop or a test utility instead of the modality, connect the printer directly to a known computer instead of the hospital network, use the other tray. Measurement closes the case: a supply rail, a fan that turns stiffly by hand, a drum temperature with a calibrated probe, a sensor state on a service display.

At Level 2 you will see service tools, configuration pages and calibration menus. Seeing them is not permission to use all of them. Change only what the manufacturer's procedure for your authorised level allows, and save the configuration before you touch it. A reset to factory settings can cure a corrupted configuration, as this lesson's case shows, but it also erases the network entries, sender profiles, LUT choices and tray settings, so it is only a repair if you have a backup or a written record to rebuild from. Do not use passwords or service keys you were not given, do not copy configuration from another serial number, do not change film-region or licence settings, and do not silence a maintenance reminder without doing the maintenance. When you reach the edge of your authority, stop and hand over a package: logs, counters, test prints with readings, what you excluded and what you suspect.

On-site checklist

• Save the error history, logs and counters before any restart.
• Check the clock, date and whether settings returned to defaults.
• Look at the film box, store and loading before the machine.
• Make an internal flat grey and step-wedge print and measure base fog, mid-grey, Dmax and left-right balance.
• Split by tray, film size, cold start versus warm, and direction of the artefact.
• Print from a second sender or a test utility to separate host from imager.
• Back up the configuration before any change, and stay within your authorised level.

Check yourself