Poljot Stadium 2628H Service Guide: Full Calendar Movement with Pusher Date Correction

The Poljot Stadium: Service Guide for the 2628H Caliber with Full Calendar and Pusher Date Correction

"Some movements reward careful attention; others demand it absolutely..."
— Reflections from the workbench

From a technician's perspective, watches divide naturally into categories based on service complexity. Some movements flow through disassembly and reassembly almost effortlessly. Others require heightened attention at specific stages. And then there are calibers that demand sustained concentration throughout, where the engineering elegance that makes them interesting also makes them unforgiving of careless handling.

The Poljot caliber 2628H belongs firmly in this last category. Known among collectors by its case style designation "Stadium," this seventeen-jewel movement incorporates a full calendar displaying both day of week and date, with the distinctive feature of pusher-actuated rapid date correction. The calendar mechanism represents a unique engineering approach within Soviet horology, mounting directly to the main plate rather than existing as a separate module. This integration creates a compact assembly but demands particular care during service.

The specimen examined here arrived in severely deteriorated condition, its lubricants congealed and components immobilized. Yet inspection confirmed all parts remained sound, justifying the considerable effort required for proper restoration. What follows documents that process with particular attention to the calendar mechanism's distinctive requirements.

Case and External Features

The Stadium case employs an unusual tonneau form that distinguished it from contemporary Soviet production. Despite significant surface deterioration, the watch retains visual interest as a vintage artifact. More relevant to service, the case incorporates features directly related to the calendar mechanism that require understanding before disassembly.

Poljot Stadium watch showing overall condition — Overall condition showing the distinctive Stadium case profile with its characteristic shape

The crown operates in two positions following standard Soviet practice, providing winding and time-setting functions. The calendar mechanism, however, receives its own dedicated control.

Crown detail showing two-position operation — The two-position crown providing winding and time-setting functions

The date correction pusher mounted at the eight o'clock position represents this caliber's distinguishing external feature. Pressing this button advances the date disk by one position, enabling rapid correction without cycling the hands through twenty-four hours for each day requiring adjustment. This convenience comes at the cost of additional mechanical complexity within the movement.

Date correction pusher at eight o'clock position — The date correction pusher at eight o'clock, the external interface to the integrated rapid-set mechanism

The case back secures with a threaded ring compressing a gasket, providing splash resistance appropriate for daily wear. The "splash resistant" rating indicates protection against incidental moisture rather than immersion capability.

Case back with threaded ring and gasket — The threaded case back ring and gasket providing the movement's moisture protection

Movement Identification

Opening the case back reveals the caliber 2628H with its seventeen-jewel specification marked in Latin characters for export identification. The "SU" designation indicates post-1980 manufacture, providing approximate dating for this example.

Movement showing 17 jewels marking and SU designation — The movement displaying its seventeen-jewel specification and SU production marking

Caliber designation 2628H visible on movement — The caliber designation 2628H clearly marked on the movement

Extraction from Case

Stem removal proceeds via the standard release button, though the accumulated contamination becomes immediately apparent as debris trails from the withdrawn stem.

Stem release button location — The stem release button providing access for stem withdrawal

Contamination visible on withdrawn stem — The withdrawn stem trailing accumulated contamination, indicating the movement's overall condition

Movement extracted with detached hands — The movement extracted from the case, hands having detached during removal

The case interior reveals the pusher mechanism from within. The internal button face interfaces with a transfer lever in the movement, transmitting the correction impulse to the calendar mechanism.

Case interior showing pusher mechanism — The case interior showing the date pusher extending through its port

Pusher retaining ring detail — The pusher secured by a spring retaining ring, serviceable in place during case cleaning

Pusher button external view — The pusher button externally, a movement-mounted spring providing return force

Disassembled case components — The case components separated from the movement in its plastic mounting frame

Movement Preparation

The movement mounts within a plastic frame secured by two screws with retaining tabs. This frame provides shock isolation and positions the movement correctly relative to the pusher port.

Movement mounting tabs — The screw-secured tabs retaining the movement within its plastic frame

Movement separated from frame — The movement freed from its mounting frame

A critical detail appears at this stage: the calendar transfer lever that interfaces with the case pusher. This lever, unique to the 2628H, transmits external button presses to the date advance mechanism. An intermediate positioning ring between the main plate and dial carries a relief that must align with this lever. Misalignment prevents proper pusher function.

Calendar transfer lever and positioning ring — The calendar transfer lever with its associated positioning ring, alignment critical during reassembly

The dial in this specimen was found unsecured, the retaining screws having loosened during the watch's service life. The dial assembly lifts away together with the positioning ring.

Dial and ring removed — The dial and positioning ring removed as a unit, the securing screws requiring attention during reassembly

Examination of the dial reveals its nature as a decorative overlay rather than a complete dial. The actual time scale appears as an oval track printed on an element mounted within the case itself. The removable component carries only the brand identification and supplementary markings.

Dial underside showing construction — The dial underside revealing its function as a decorative overlay rather than complete dial

Calendar Mechanism Disassembly

The calendar mechanism demands careful attention during disassembly. Small springs and precisely positioned components require systematic removal with attention to their installation orientation.

The day-of-week disk removes first, secured by a spring retaining washer.

Day disk retaining washer — The spring retaining washer securing the day-of-week disk

Retaining washer removed — The retaining washer lifted from its position

Day disk removed — The day-of-week disk removed from the movement

Day disk underside — The day disk underside showing its driving teeth

The day disk detent lever follows, requiring careful release of its positioning spring before removal. This lever exhibits a complex profile essential to proper calendar function.

Day detent lever spring release — Releasing the day detent lever positioning spring

Spring released from detent lever — The spring freed from the detent lever

Day detent lever removed — The day detent lever with its spring, the lever's complex profile visible

The calendar plate now lifts away, exposing the date disk beneath.

Calendar plate and date disk — The calendar plate with the date disk visible beneath

Calendar plate underside — The calendar plate underside showing its bearing surfaces

A critical warning: a small positioning spring resides within the calendar plate assembly. This spring does not launch during removal but will fall free if the plate is inverted carelessly. Its dimensions make recovery difficult should it escape to the floor. Note its installed orientation carefully.

Critical positioning spring in calendar plate — The critical positioning spring within the calendar plate, its orientation requiring careful documentation

Calendar mechanism exposed — The calendar mechanism fully exposed following plate removal

The Integrated Date Correction Mechanism

The rapid date correction system distinguishes the 2628H from other Soviet calendar calibers. Unlike the Slava approach where date correction exists as a separate module added to the basic movement, the Poljot design integrates this function directly into the main plate architecture. The result is elegant but demanding.

The mechanism comprises a transfer lever receiving pusher input, a complex actuator assembly, and an R-shaped return spring similar in concept to those employed in keyless works. The actuator consists of two articulated sections that translate button pressure into rotational impulse on the date disk.

Date correction mechanism components — The date correction mechanism: transfer lever, articulated actuator, and R-spring

The command wheel and date advance lever mount nearby. In this specimen, prior service attempts had displaced these components from their correct positions, requiring careful restoration during reassembly.

Command wheel and advance lever — The command wheel and date advance lever, found displaced from their proper positions

Removing the calendar wheel cover exposes the motion works and intermediate wheels.

Calendar wheel cover removal — The calendar wheel cover lifted to expose the underlying wheel system

Motion works exposed — The motion works visible following cover removal

Calendar wheel train components — The calendar wheel train: two intermediate wheels, intermediate wheel, and two-tier hour wheel

Minute wheel removed — The minute wheel following removal

An unexpected discovery during disassembly: the broken post of a previous seconds hand remained pressed onto the fourth wheel arbor. This required careful extraction before reassembly.

Broken seconds hand post on fourth wheel — The remnant of a broken seconds hand still mounted on the fourth wheel arbor

Broken post removed — The broken post extracted from the arbor

Fourth wheel arbor straightened — The fourth wheel arbor straightened following post removal, gentle correction preventing further damage

Calendar components disassembled — The complete calendar mechanism disassembled, components arranged for cleaning

Going Train Disassembly

With the calendar mechanism cleared, disassembly proceeds to the going train. The Poljot 26xx series employs standard Soviet architecture familiar from previous examinations.

Going train ready for disassembly — The going train exposed and ready for disassembly

The balance assembly presents standard construction with movable stud carrier and shock protection. The customary timing washer appears in its expected position.

The pallet fork and bridge follow standard Poljot practice for the 26xx series.

Pallet fork assembly — The pallet fork assembly typical of Poljot 26xx calibers

Pallet fork components — The pallet fork with its bridge and securing screws

The mainspring motor disassembles quickly. Note the left-hand thread on the ratchet wheel, indicated by three radial marks on the screw head.

Mainspring motor with left-hand thread indicator — The mainspring motor, the three marks indicating left-hand thread on the ratchet wheel screw

Going train before bridge removal — The gear train prior to bridge removal

Train bridge removed exposing wheels — The train bridge removed, exposing the seconds wheel, intermediate wheel, and escape wheel

Train wheels removed — The train wheels extracted for cleaning

Center wheel removal — Removing the center wheel and its bridge

Center wheel components — The center wheel with its bridge

Going train side cleared — The going train side of the movement cleared

The keyless works require mention of a Poljot-specific detail: two spring covers secure the setting mechanism rather than the single cover common in other calibers.

Keyless works with two spring covers — The keyless works showing the two-cover arrangement typical of Poljot calibers

First keyless cover removed — The first keyless works cover lifted

Keyless components exposed — The keyless mechanism components exposed

Keyless works disassembled — The keyless works fully disassembled

Complete disassembly — The movement completely disassembled, ready for cleaning

Cleaning and Mainspring Service

The mainspring barrel reveals the extent of lubricant degradation throughout the movement.

Dirty mainspring barrel — The mainspring barrel showing accumulated contamination

The mainspring employs the desirable S-curve profile, a quality indicator in Soviet movements.

S-curve mainspring — The S-profile mainspring extracted for cleaning

Calendar plate spring during cleaning — The critical calendar plate spring secured during the cleaning process

Cleaned mainspring and barrel — The mainspring and barrel restored to proper condition

Mainspring bridle detail — The sword-profile mainspring bridle

Mainspring installed and lubricated — The mainspring reinstalled with fresh lubricant, barrel ready for assembly

Reassembly: Going Train

Reassembly begins with the main plate and center wheel, working outward through the gear train. Moebius 8000 provides bearing lubrication throughout.

Main plate and lubricant prepared — The cleaned main plate with Moebius 8000 prepared for assembly

Center wheel installation — The center wheel positioned in its bearing

Center wheel bridge installed — The center wheel bridge securing the first train component

The minute wheel installs from the dial side, preparing for motion works and calendar assembly.

Minute wheel installation — The minute wheel positioned from the dial side

Motion works wheel system — The motion works wheel system arranged for installation

Motion works and keyless assembly — The motion works installed with keyless mechanism components positioned

Keyless works complete — The keyless works secured beneath both spring covers

The gear train wheels install with their bridge. The Poljot layout positions these wheels in a configuration that complicates bridge installation, requiring careful manipulation to engage all pivots simultaneously.

Train wheels positioned — The train wheels positioned in their bearings

Train bridge installed — The train bridge successfully installed despite the challenging wheel positioning

Mainspring motor assembled — The mainspring motor assembled and installed

Pallet fork installation follows standard practice: the fork pivots receive no lubrication, while the pallet stone impulse faces require careful oil application.

Pallet fork installed — The pallet fork installed, stone faces lubricated while pivots remain dry

Balance cap jewel service — The balance cap jewel assembly serviced with fresh lubricant

Lower cap jewel lubrication — Lower balance cap jewel lubricated before calendar assembly obscures access

Reassembly: Calendar Mechanism

Calendar assembly demands precise attention to component positioning. The date advance lever installs first, its accumulator spring carefully handled to prevent deformation.

Date advance lever installation — The date advance lever positioned with its accumulator spring, orientation critical

The command wheel follows, its eccentric requiring alignment with the advance lever.

Command wheel installation — The command wheel installed with eccentric properly aligned to the advance lever

The pusher actuator mechanism presents the most demanding installation. The articulated components must engage correctly while the R-spring remains captured. These springs share the launching tendency common to all similar components.

Pusher actuator installation — The pusher actuator mechanism positioned, R-spring requiring careful retention

Calendar mechanisms complete before date disk — All calendar actuation mechanisms in place, verified before date disk installation

With actuation mechanisms verified, the date disk mounts in position.

Date disk installed — The date disk installed on the calendar mechanism

Only after the date disk is in place can the date detent lever and its R-spring be installed. Reversing this sequence results in component displacement and potential part loss.

Date detent lever installation — The date detent lever positioned after date disk installation

Date detent R-spring installed — The R-spring securing the date detent lever, completing this assembly phase

The calendar plate with its critical positioning spring now covers the mechanism.

Calendar plate with spring — The calendar plate with its positioning spring, ready for installation

Calendar plate installed — The calendar plate secured over the date mechanism

Calendar spring positioning — Correct positioning of the calendar plate spring, essential for proper function

The day-of-week assembly completes the calendar: detent lever, day disk, and retaining washer install in sequence.

Day mechanism complete — The day-of-week mechanism assembled on the calendar plate

The positioning ring and dial return with careful attention to the ring's orientation relative to the pusher transfer lever.

Positioning ring alignment — The positioning ring correctly oriented, its relief aligned with the pusher transfer lever

Dial securing screws — The dial foot securing screws properly tightened, correcting the previous loose condition

Final Assembly and Results

With the calendar complete, the balance installs and the movement comes alive.

Balance installation — The balance wheel returning to position, completing the movement assembly

Upper cap jewel service — Final attention to the upper balance cap jewel

A service date inscription documents the restoration for future reference.

Movement ready for case — The serviced movement ready for case installation

The completed restoration returns a mechanically excellent movement to service, housed in a case that honestly reflects its age. A replacement seconds hand in the correct red color completes the dial presentation.

Timing results — Timing machine verification confirming satisfactory performance following service

Technical Observations

The Poljot caliber 2628H represents a distinctive approach to full calendar mechanism design within Soviet horology. By integrating the rapid-set date correction directly into the main plate architecture, the engineers achieved a compact solution that avoids the module-upon-module construction seen in comparable Slava calibers. The cost appears in service complexity: multiple springs, precisely positioned levers, and interdependent components that punish careless handling.

The seventeen-jewel specification indicates a movement of moderate grade, adequate for reliable timekeeping without premium pretension. The S-curve mainspring and standard shock protection represent quality appropriate to the intended market positioning.

For technicians encountering this caliber, the calendar mechanism demands respect. Components must be removed and installed in specific sequences. Springs require careful handling and documentation of their installed orientations. The pusher transfer lever and positioning ring alignment deserves verification before the watch returns to service. Patience invested during assembly prevents frustrating disassembly to correct oversights.

The Stadium case design, distinctive in its era, houses a movement worthy of the attention its calendar mechanism requires. For collectors seeking interesting Soviet complications in unusual presentations, this combination offers genuine appeal.