Chapter 54: Blind Welds and Margins

13:40. Laboratory. The iron door swung open. Cold air rolled in with the smell of rosin and old rubber. It stung his nose. Lin Chen stepped over the threshold. His weight settled on his right foot. His left foot hovered half an inch off the floor. The gauze on his sole rubbed against the inside of his shoe. A dull pain came from the scabbed wound. He ignored it. Smoothed out his breathing.

A long table. Covered with a black anti-static mat. Fine grid across the surface. On the table lay the kit: a perforated board. Resistors and capacitors. Wires. A soldering-iron stand. Solder wire. A block of rosin. Old Li stood behind the lectern. Two black cloths in his hands.

"Additional practical test. Rules changed." Old Li's voice was flat. Without inflection. "Close your eyes. Or blindfold yourselves. Complete the soldering of a voltage-regulator circuit by touch and memory. Time limit: forty minutes. If your pass rate for solder joints is below eighty percent, points will be deducted from your bonus score. Above ninety-five percent, extra points. Timer starts now. Come get your blindfolds."

The crowd stirred. Someone swallowed. Someone's fingers trembled. Lin Chen walked forward. Took a black cloth. The fabric was coarse. The edges frayed. He returned to his seat. Opened his canvas bag. Took out his homemade soldering iron. Plugged it in. Let it preheat. The copper tip glowed faintly red. He brought the rosin close. White smoke rose. The smell was familiar. He closed his eyes.

Darkness fell. Vision severed. Every other sense was forced wider.

He reached out. His fingertips touched the anti-static mat. Grid texture. Located the center. His left hand searched. The perforated board. Sharp edges. Hole spacing: 2.54 millimeters. Standard pitch. He counted holes. Across. Down. Built a coordinate system. Origin. First hole in the upper left corner.

His right hand moved toward the parts box. Resistors. The color bands were useless now. He pinched one. Rolled it between thumb and forefinger. Judged size. Wattage. Quarter-watt. Slim. Resistance unknown to the eye, but the circuit diagram had already hardened in his mind. R1. 1kΩ. R2. 2.2kΩ. R3. 10kΩ. He distinguished them by feel. The 1kΩ was slightly thicker. The 2.2kΩ standard. The 10kΩ long and fine. He placed them into their corresponding holes.

Capacitor. Cylindrical body. Polarity. Long lead positive. Short lead negative. He pinched it. Ran a fingertip over the leads. Difference in length: about two millimeters. Confirmed. Inserted.

Transistor. TO-92 package. Half-cylinder. Flat side facing left. Lead order. E. B. C. He found the flat face. Set the orientation. Inserted it.

His movements were slow. But steady. No rushing. No bumping anyone else. In the darkness there was only the faint sound of metal leads scraping across the perforated board. And breathing kept low. Someone's hands shook. A component dropped. A crisp clatter. Someone cursed under his breath.

Lin Chen paid no attention. His fingers kept moving. Wiring. Stripping the insulation. Leaving enough length. Bending. Inserting. Securing.

The soldering iron. In his right hand. Temperature stable now. 350°C. He judged it by feel. The copper tip approached the pad. Not touching yet. Hovered for half a second. Felt the radiating heat. Hot enough.

Pressed down. The tip touched the lead and pad at the same time. Two seconds. Rosin melted. A wisp of white smoke rose. Sharp smell. His left hand fed solder. The wire touched the iron tip. Melted. Flowed into the pad. Pulled away. Solidified.

Hearing joined in. The hiss of molten solder. Short. Even. No crackle. That meant the temperature was right. No cold joint.

Touch joined in. The joint had formed. Conical. Smooth surface. No burrs. He brushed it lightly with a fingertip. Slightly raised. Not sharp. Acceptable.

He moved on. The next joint. Repeated. Position. Heat. Feed solder. Withdraw. Inspect.

Time passed. In the dark there was no light. Only touch. Temperature. Sound. Smell. Four lines, crossing in his mind. Not colliding. Not tangling. Each moving forward on its own.

His foot hurt. He adjusted his posture. Shifted more weight to the right. Left leg suspended, keeping pressure off the injury. His fingers were going numb from the cold. He breathed warm air onto them. White mist dispersed. Continued.

Old Li's footsteps moved down the aisle. Stopped behind him. Breathing close. No comment. Only the stopwatch. Tick. Tick.

The thirty-second joint. The transistor's collector. Cramped space. Dense leads. His fingertips reached in. Felt for position. Off by half a millimeter. He adjusted the angle of the iron slightly. Let the beveled face settle in. Heated. Fed solder. Withdrew.

A hiss. Short. Even.

He kept his eyes closed. Touched it lightly with his fingertip. Full joint. No bridging. Acceptable.

The last wire. Power input. Positive and negative. He pinched them. Red and black. The insulation thickness was different. The red wire was slightly thicker. Positive. The black slightly thinner. Negative. Inserted. Secured.

Power-on test. He found the switch. Pressed it.

A hum. Faint current noise. No explosive short-circuit pop.

He found the multimeter. Plugged in the probes. Touched the output terminals. The needle swung. He read the scale by feel. 5.0V. Stable. No drift.

He released the probes. Cut the power. Set down the soldering iron.

"Time's up. Hands off. Remove the blindfolds."

Old Li's voice rang out. Power cut. Silence in the lab.

Lin Chen opened his eyes. Light stabbed in. His pupils contracted. He adjusted. Took off the black cloth. Set it on the desk. The solder joints were lined up neatly. The sheen of solder glimmered faintly. No cold joints. No burrs. No bridging.

Old Li came over. Magnifying glass in hand. Bent down. Examined. His gaze passed over every joint. Paused. Gave no comment. Only recorded.

Then he moved to the next table. Continued.

Lin Chen sat down. His fingers were a little stiff. Red marks had been pressed into his fingertips. He rotated his wrist. The joints gave a faint click. His breathing stayed even. Chest rising and falling. Fixed rhythm.

14:40. Grading finished.

Old Li returned to the lectern. A form in his hand. Rough paper. Curled edges.

"Additional practical test. Results." He read names. No inflection. "Lin Chen. Solder-joint pass rate. Ninety-eight percent. Power-on test. 5.01V. Error: 0.01V. Blind soldering. Extra bonus points. Total score. First in bonus points."

The crowd stirred. Some lowered their heads. Some clenched their fists. Some looked at him with complicated eyes.

Old Li kept reading. Names. Scores. Rankings. No extra words.

"Tomorrow. Final winter-camp evaluation will be announced. Resources will be allocated according to ranking. Group A. Guaranteed spots for the provincial competition. Group B. Recommendations to key city high schools. Group C. Completion only. No recommendation."

He put away the form. Turned. Left. Footsteps receding.

The lab went quiet. Only the sound of equipment being packed away. And hushed discussion.

Lin Chen stood. Tidied his workspace. Returned components to their places. Unplugged the soldering iron. Let it cool. Put it into his canvas bag. Pulled the zipper shut. Weight evenly distributed.

He pushed open the door. Left. The hallway was cold. Wind poured up from the stairwell. Carrying the smell of chalk dust and old wood.

16:00. Back to the dormitory. He pushed the door open. Locked it behind him. Set the canvas bag on the bed. Light movement.

He spread open his ledger. Pencil moving across the page.

Day 32. 16:15. Additional practical test finished. Blind-soldering pass rate: 98%. First in bonus points. Funds: 1.19 yuan. Surplus. Next step: final evaluation announced. Resource allocation. Provincial competition slots.

The pencil tip paused. He closed the ledger.

He stood and went to the washroom. Cold water. Piercing. Washed his face. The towel was rough. Scraped his skin. Left red marks. Kept him awake.

Back in the room. Sat down. Closed his eyes. There were no formulas in his mind. Only rankings. Quotas. Resources. Three lines crossing in the dark. Not colliding. Not tangling. Each moving forward on its own.

He opened his eyes. His gaze fell on the windowsill. A notice. Somehow slipped through the crack in the door. The paper had yellowed. Creases along the edges.

He walked over. Picked it up. Opened it.

Supplementary Notice from the Municipal Education Committee: For this winter camp's final evaluation, in addition to theory and practical work, an extra category of "family background and overall qualities" has been added. Recommendation comments will be submitted by the teacher leading each school's team. Weight: ten percent. In addition, students entering the provincial competition training camp must provide their own oscilloscope, multimeter, and basic component kit. Estimated budget: about 80 yuan. Those unable to prepare all required items will not be admitted.

His fingers tightened. The edge of the paper curled.

Eighty yuan. Family background. Recommendation comments.

He closed his eyes. There was no complaint in his mind. Only equations. Gap. Paths. Countermeasures.

He opened his eyes. His gaze fell beneath the bed. An old tin box. Inside were parts traded from the scrap station. And half a length of copper wire.

He pulled out an old notebook. Blank page. Pencil moving.

Funding gap: 78.81 yuan. Countermeasures: 1. Scrap station. Copper wire. Aluminum housings. Old appliances. Dismantle. Sell. 2. Cafeteria. Wash dishes for others. Exchange for cash. 3. Group A classmates. Pool orders. Purchase together. Push down the price. 4. Recommendation comments. Homeroom teacher. Old Li. Need to talk.

The pencil tip paused. He closed the notebook. Fingers tightening. The page edges curled. He shoved it into the bottom of his bag. Pinned it there.

Outside the window. The sky darkened. Clouds hung low. Snow had not yet fallen. Wind passed through the gaps. Letting out a low whine.

The broadcast speaker. Static. Buzzing. Old Li's voice, distorted. Coming through the walls.

"Tomorrow. 07:00. Assemble on the sports field. Final evaluation list will be announced. Anyone absent will be treated as having withdrawn voluntarily."

The current cut. Silence in the dorm.

Lin Chen opened his eyes. His gaze fell on the side pocket of the canvas bag. Dried tangerine peel. Old newspaper. He reached into his inner pocket. Receipt. Red stamp. Fifty yuan. Already paid. But the road ahead was not smooth. Ranking. Quotas. An eighty-yuan gap. Recommendation comments. He needed to calculate. Time. He needed to squeeze it out.

He stood. Went to the washroom. Cold water. Piercing. Washed his face. The towel was rough. Rubbing his skin. Leaving red marks. It did not hurt. It kept him awake. Back in the room. He spread out a fresh sheet of graph paper. Pencil. Ruler. Drew axes. Marked scales. No sketching. No shading. Lines straight. Even. He closed his eyes. There were no curves in his mind. Only solder joints. Temperature. Time. Molten solder. Solidification. Three lines crossing in the dark. Not colliding. Not tangling. Each moving forward on its own.

He opened his eyes. His gaze settled on the graph. The first stroke came down. Steady. No tremor.

Coordinate axes. Horizontal axis: time. Vertical axis: funds. Origin. Zero point. Scale marks. Each square: 10 yuan. 1 day. He calculated. Current: 1.19. Target: 80. Gap: 78.81. Linear. Positive slope. He drew the line. No bends. No breaks. Pencil dust fell onto the paper. He wiped it lightly with the eraser. No trace left.

His foot hurt. He changed posture. Shifted his weight to the right leg. Left leg suspended, keeping pressure off the injury. His fingers were stiff with cold. He breathed warm air onto them. White mist dispersed. Kept drawing.

Outside the window. The wind died. The grains of snow grew finer. Ticked against the glass in a scatter of tiny taps. Everything was being leveled flat. Leaving only white. And cold.

Tomorrow. Seven o'clock. Final evaluation.

He closed his eyes. Slept. But his hand kept moving. His fingertips traced a circuit diagram across the bedsheet, unconscious. Power supply. Current limiting. Load. Feedback. Nodes. Loop. Ground. Lines straight. Even. Unshaking.

Tick. Tick.