DRDO CEPTAM Tech-A common mistakes
DRDO CEPTAM Tech-A · Understand the traps and how to avoid them.
In the Fitter section, mixing up the clearance, allowance and tolerance of a fit and answering 'allowance' when the question asks for the intentional difference in sizes between mating parts before assembly.
The three terms are taught together and sound interchangeable; candidates memorise the definitions as a block rather than linking each term to a distinct measurement (allowance = minimum clearance or maximum interference; tolerance = permissible variation of one dimension).
What to do instead
Build a one-page comparison table with the three terms, their formulas and one worked numeric example each, and practise classifying 20 short statements into 'clearance', 'allowance' or 'tolerance' before attempting full questions.
In the Electrician section, applying the wrong formula to a series-parallel resistor network and picking an answer that matches a distractor computed by treating all resistors as parallel.
Under time pressure candidates pattern-match on the sight of resistors and jump to 1/R = 1/R1 + 1/R2 + ..., skipping the step of identifying which branches are actually in series.
What to do instead
Before calculating, redraw the network marking nodes with letters and reduce it step by step from the innermost series pair outward; keep a running note of each reduced value so the final total can be checked against the smallest and largest branch values.
In the Welder/Machinist/Turner section, confusing welding-symbol positions or electrode coding, and confusing cutting speed, feed and depth of cut when calculating machining time.
Trade theory is revised from diagrams that candidates skim; the standard placement of the weld symbol relative to the reference line, and the units of feed (mm/rev) versus cutting speed (m/min), are rarely practised numerically.
What to do instead
Redraw the standard welding symbol from memory daily, labelling each element, and solve at least ten machining-time problems using T = L/(f x N) with unit checks written out, converting cutting speed to rpm explicitly each time.
In the Electronics/Instrumentation/Computer section, computing a transistor or op-amp circuit answer without checking the assumed operating region, so a saturated or rail-limited result is reported as if it were linear.
Textbook formulas assume active or linear operation, and candidates apply them mechanically without verifying VCE or output swing against supply rails.
What to do instead
Adopt a fixed two-line check after every calculation: state the assumed region, then test it numerically (for example VCE > 0.2 V for active mode, or output within supply rails); if the test fails, redo the problem for the saturated or clipped case.
In Quantitative Aptitude, spending more than two minutes on one DI set or arithmetic word problem and then rushing the remaining questions with arithmetic slips.
The paper rewards speed and candidates feel obliged to finish every question; sunk-cost thinking keeps them on a single hard problem while easy marks later are lost.
What to do instead
Set a hard per-question cap (about 60-75 seconds) in practice, mark and skip on the first pass, and do a second pass only on marked questions; track accuracy and time per topic in a log to identify which topics deserve the skip.
In Reasoning, treating a seating-arrangement or blood-relation puzzle as a memory test and guessing when the arrangement becomes ambiguous, instead of testing whether the given clues actually fix a unique solution.
Candidates have seen similar puzzles and assume the standard layout applies; they do not check for multiple valid arrangements or for the 'cannot be determined' option.
What to do instead
For every puzzle, write all clues as constraints, draw the base layout, and after placing entities verify each clue against the diagram; if two arrangements satisfy all clues, select 'cannot be determined' rather than forcing one.
In General Awareness and General Science, relying on rote lists of dates, awards and scientific units without connecting them, and answering 'Newton' for force-related unit questions that actually ask for work or power.
Preparation is often done by reading compilations passively; units and definitions are stored as isolated labels, so near-miss distractors (joule vs newton, watt vs joule) look familiar.
What to do instead
Convert lists into paired flashcards (quantity-unit-symbol-formula) and self-test in both directions; for science, derive the unit from the formula (work = force x distance, so joule = newton-metre) rather than recalling it separately.
In English Language, choosing an answer by how natural a sentence sounds rather than by grammar rules, so errors in subject-verb agreement, articles and prepositions slip through, and cloze blanks are filled one by one without reading the whole passage.
Everyday spoken English tolerates errors that the exam marks wrong; candidates also read options before forming their own answer, which biases them toward a familiar-sounding distractor.
What to do instead
For error-spotting and fill-in questions, cover the options, predict the answer, then compare; for cloze tests, read the full passage once for theme, then answer, checking each blank against the sentence's subject and tense.
In any technical section, ignoring the trade-specific units and significant figures, so an answer in millimetres is marked from a calculation done in metres, or a result is rounded differently from the options.
Technical questions often mix mm, cm and m, or rpm and rad/s, and candidates carry numbers through without converting; option sets are built to punish exactly this.
What to do instead
Write the unit beside every number at each step and convert to SI before substituting; after obtaining the result, re-express it in the unit used by the options and check magnitude against a rough estimate.
Attempting the paper in strict question order across all sections, so a weak technical section consumes time that would have earned more marks in Quantitative Aptitude or Reasoning.
Candidates prepare section-wise but never rehearse the paper as a whole; without a mock-based time plan they default to sequential order.
What to do instead
Run at least three full-length timed mocks and decide a fixed section order based on measured marks-per-minute per section; in the exam, execute that order and leave the weakest section for last, with a reserve of 10 minutes for review.