Cryostats

Leica CM1850: troubleshooting and error codes

The ServiceForge knowledge base holds 36 documented symptoms for the Leica CM1850, with 87 ranked causes, 16 diagnostic checks with test points and expected values, and 8 error codes. Each symptom below shows its causes and the first check; the rest is one connection away. Connect ServiceForge to your AI

Symptoms

Ridged sections

Cut sections exhibit ridge marks or ridged patterns.

Ranked causes

1. Specimen insufficiently frozen onto specimen disc (common)
2. Specimen disc not clamped tightly (common)
3. Specimen holder ball joint not clamped (common)
4. Knife/blade not clamped tightly enough (common)
5. Specimen detached from disc due to excessive thickness (occasional)
6. Very hard or inhomogeneous specimen (occasional)
7. Blunt knife/blade (occasional)

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

Sections not properly flattened

Cut sections fail to flatten properly or exhibit wrinkles and waves.

Ranked causes

1. Anti-roll plate poorly positioned (common)
2. Anti-roll plate poorly aligned with knife edge (common)
3. Incorrect clearance angle (common)
4. Knife/blade blunt or damaged (common)
5. Knife/blade and/or anti-roll plate dirty (occasional)
6. Edge of anti-roll plate damaged (occasional)
7. Blunt knife/blade (occasional)

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

Chatter during sectioning

Vibration or chattering sound during the cutting motion.

Ranked causes

1. Knife profile inappropriate for specimen (common)
2. Incorrect clearance angle (common)
3. Ice buildup in knife back (occasional)
4. Handwheel speed not uniform (occasional)
5. Knife/blade not clamped tightly enough (occasional)
6. Specimen holder not clamped tightly (occasional)

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

Thick-thin sections

Sections vary in thickness, alternating between thick and thin cuts.

Ranked causes

1. Cryocompound applied to cold disc, specimen detached after freezing (common)
2. Blunt cutting edge (common)
3. Incorrect clearance angle (occasional)
4. Microtome not properly dried before reinstallation (occasional)
5. Dried specimen (occasional)

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

No or insufficient refrigeration caution

Cooling output is reduced or absent; chamber does not reach set temperature

Ranked causes

1. Compressor defective (common)
2. Leak in cooling system (common)
3. Inappropriate site conditions (occasional)
4. Ventilation slits of liquefier dirty (occasional)

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

Sections splinter

Cut tissue sections break or splinter into fragments during sectioning.

Ranked causes

1. Specimen too cold (common)
2. Static electricity or air currents affecting specimen (occasional)
3. Specimen not cold enough (occasional)
4. Large area specimen (occasional)

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

Sections tear

Tissue sections tear or shred during cutting rather than producing clean sections

Ranked causes

1. Blunt part, dirt, dust, frost or rust on knife/blade (common)
2. Leading edge of anti-roll plate damaged (occasional)
3. Hard particles in tissue (rare)
4. Knife back dirty (occasional)

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

Tissue sticks or crumbles on anti-roll plate

Tissue material adheres to or breaks apart on the anti-roll plate surface.

Ranked causes

1. Temperature incorrect for tissue being cut (common)
2. Knife profile inappropriate for specimen (common)
3. Anti-roll plate too warm or incorrectly positioned (occasional)
4. Static electricity affecting tissue (occasional)

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

Compressor startup current requirement not met high voltage

Nominal voltage drops below specified values during compressor start-up, instrument may not operate properly or sustain damage due to insufficient power supply capacity

Ranked causes

1. Electric circuit at installation site does not meet start-up current requirements (common)
2. Other consumers connected to same circuit (occasional)
3. Inadequate or unstable mains power supply (occasional)

First check

Verify electric circuit capacity with electrical engineer

Test point: Installation site power supply
Expected: Circuit rated for minimum 45-50 A start-up current and stable nominal voltage per Technical data

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

Cryostat inoperational caution

Unit does not cool or operate; no refrigeration function

Ranked causes

1. Mains plug not properly connected (common)
2. Defective fuses (common)
3. Temperature control switch activated (occasional)

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

Fat on corner or edge of anti-roll plate

Visible fat deposits on anti-roll plate surfaces during sectioning

Ranked causes

1. Rusty knife/blade (common)
2. Static electricity or air currents (occasional)
3. Anti-roll plate too warm (occasional)

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

Frost on chamber walls and microtome

Visible frost accumulation on interior surfaces of the cryochamber and microtome.

Ranked causes

1. Cryostat exposed to air currents from open windows and doors, or air conditioning (common)
2. Sliding window left open too long, exposed to air currents (common)
3. Frost built up from breathing into cryochamber (occasional)

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

Ice formation on bottom of cryochamber

Accumulation of ice at the base of the cryochamber.

Ranked causes

1. Condensation water drain obstructed (common)
2. Drain of quick freeze shelf defrosting water obstructed (common)
3. Cryostat not aligned level (occasional)

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

Compressor start-up current exceeds supply capacity high voltage

Instrument may not start or operate smoothly if electrical supply cannot deliver required current during compressor initialization.

Ranked causes

1. Electrical circuit undersized or inadequate for compressor startup current (common)
2. Nominal voltage drops below specified minimum during startup (common)

First check

Verify electrical circuit capacity and specifications

Test point: Installation site main circuit breaker and wiring
Expected: Circuit rated for 45–50 A startup current and capable of maintaining nominal voltage per instrument nameplate

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

Inconsistent or insufficient specimen feed

Specimen advance is erratic, slow or stops intermittently during sectioning cycle

Ranked causes

1. Microtome not entirely dry; ice in micrometer feed system (common)
2. Defective microtome (rare)

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

Instrument damage due to inadequate power supply high voltage

Continuous or unstable power supply causes equipment failure

Ranked causes

1. Inadequate or interrupted power supply to instrument (common)
2. Other consumers sharing the electrical circuit (occasional)

First check

Verify electrical circuit is dedicated and protected

Test point: installation site circuit breaker and wiring
Expected: Separate dedicated circuit with appropriate protection, no shared loads

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

LED (2) does not illuminate at front limit

LED (2) on advance button fails to illuminate when specimen reaches front limit

Ranked causes

1. LED (2) burned out or disconnected (unknown)
2. Front limit switch not triggering (unknown)

First check

Observe LED (2) behavior during specimen advance to front limit

Test point: LED (2) on advance button and front limit position
Expected: LED (2) illuminates when specimen reaches front limit

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

Scraping noise during sectioning and specimen return movement

Audible scraping or grinding sound during cutting and return movement of the microtome.

Ranked causes

1. Knife/blade damaged (common)
2. Edge of anti-roll plate damaged (common)

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

Sections curl on anti-roll plate

Cut tissue sections curl or wave on the anti-roll plate instead of lying flat.

Ranked causes

1. Anti-roll plate does not protrude far enough beyond cutting edge (common)
2. Anti-roll plate protrudes too far and scrapes specimen (common)

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

Sections smear

Cut tissue sections are smeared or dragged during sectioning.

Ranked causes

1. Specimen not cold enough (common)
2. Knife/blade and/or anti-roll plate not yet cold enough, warming sections (common)

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

Specimen does not return to rear limit

Specimen fails to move rearward when return button is pressed; LED (1) should flash during rapid return or slow return buttons pressed

Ranked causes

1. Rapid or slow return button not functioning (unknown)
2. Return movement blocked or stalled (unknown)

First check

Test rapid return button for LED (1) response

Test point: Return button and LED (1) on control panel 2
Expected: LED (1) flashes while specimen head is in motion; illuminates steady when rear limit reached

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

Anti-roll plate damage after adjustment

Anti-roll plate becomes damaged during positioning or alignment procedures.

Ranked causes

1. Plate raised too high when aligning, struck by cutting edge (occasional)

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

Condensation on anti-roll plate and knife during cleaning

Moisture and condensation form on anti-roll plate and knife surfaces during cleaning operations.

Ranked causes

1. Brush, forceps and/or cloth too warm (common)

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

Flattened sections curl up when anti-roll plate is picked up

Tissue sections begin curling immediately upon removal of anti-roll plate

Ranked causes

1. Temperature too low for tissue cut (common)

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

Fuse replacement caution

Fuses need to be replaced with correct specification to avoid equipment damage.

Ranked causes

1. Blown or faulty fuse (unknown)

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

Instrument damaged after transport caution

Severe damage to compressor and internal components following shipment and immediate power-on without waiting period.

Ranked causes

1. Compressor oil displaced during transport, not allowed to settle before startup (common)

First check

Verify waiting period observed after transport

Test point: Clock or timestamp
Expected: At least 4 hours elapsed since transport

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

Instrument does not power on

No response when automatic mains fuse switch is activated to position 1

Ranked causes

1. Instrument powered on too soon after transport (common)

First check

Verify wait time after transport

Test point: Transport completion time
Expected: At least 4 hours elapsed

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

Lamp replacement high voltage

Broken lamp requires replacement by technical service due to high injury risk.

Ranked causes

1. Lamp broken or non-functional (unknown)

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

Manual defrost of quick freeze shelf required caution

Excessive frost formation on quick freeze shelf, particularly after spray disinfection, necessitates manual defrost cycle.

Ranked causes

1. Moisture accumulation on quick freeze shelf from spray disinfection (common)

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

Microtome malfunction or damage from humidity caution

Humidity inside condenses and freezes in the cold cryostat, causing malfunctions or damage.

Ranked causes

1. Microtome not entirely dry before reinstallation (common)

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

Nominal voltage drops below specification at startup high voltage

Compressor start-up current draws 45–50 A; voltage drop occurs at installation site

Ranked causes

1. Inadequate electrical circuit capacity at installation site (common)

First check

Verify mains voltage against Technical data specifications during compressor start-up

Test point: mains power outlet at wall
Expected: Nominal voltage per Technical data, minimum threshold not exceeded

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

Scraping noise at microtome caution

Audible scraping or grinding sound during microtome operation

Ranked causes

1. Friction between slot cover and microtome housing (common)

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

Severe instrument damage from inadequate power supply caution

Failure to ensure proper electrical circuit and constant adequate power supply causes irreversible damage to the instrument.

Ranked causes

1. Inadequate or unstable power supply connected to instrument (common)

First check

Verify circuit is protected and dedicated exclusively to instrument

Test point: Installation site main circuit
Expected: Circuit has separate protection and no other loads connected

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

Severe instrument damage from power supply failure patient safety

Instrument sustains severe damage if nominal voltage drops during compressor start-up or if power supply is inadequate or unstable

Ranked causes

1. Non-compliance with power supply requirements (common)

First check

Confirm electrical engineer inspection completed

Test point: Installation documentation
Expected: Written verification that circuit meets 45-50 A requirement

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

Specimen disc cannot be removed patient safety

Specimen disc stuck to freezing shelf or specimen head and cannot be separated

Ranked causes

1. Moisture on underside froze disc to freezing shelf or specimen head (common)

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

Specimen does not advance toward knife patient safety

Specimen fails to move forward when coarse feed advance button is pressed; movement should occur as long as button is held

Ranked causes

1. Coarse feed advance button not functioning (unknown)

First check

Verify specimen can advance toward knife with coarse feed button

Test point: Advance button on control panel 2
Expected: Specimen moves toward knife as long as button is pressed

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

Error codes

Code	Meaning	Trigger	Severity
`E0:20`	Calibrating error; possibly defective controller board	Calibration failure during operation	error
`E0:21`	Clock battery on the controller board empty	Battery voltage drops below threshold	error
`E0:22`	Microtome wet	Moisture detected in microtome chamber	warning
`E0:23`	Cryochamber temperature out of range of indication	Temperature sensor reads outside -35 °C to +55 °C range	error
`E0:24`	Short circuit at temperature sensor of chamber cooling system	Sensor circuit short detected	error
`E0:25`	Breaking of temperature sensor of chamber cooling system	Sensor circuit open detected	error
`E0:26`	Short circuit at temperature sensor of evaporator	Evaporator sensor circuit short detected	error
`E0:27`	Breaking of temperature sensor of evaporator	Evaporator sensor circuit open detected	error

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.