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Recap: general method

Replacing capacitors is the most universal retro repair. On many machines (Mega Drive 2, Game Gear, PC Engine, Amiga, mono MVS, CRT chassis) it is the No. 1 cause of failure — and sometimes an emergency (electrolyte eating the board).

Why capacitors die

  • Aluminium electrolytics: the electrolyte dries out → ESR (series resistance) rises, capacitance drops → filtering fails, ripple, instability, degraded sound/video.
  • SMD electrolytics (Game Gear, MD2, PCE, Amiga…): the electrolyte leaks and corrodes traces/vias under the part → emergency: the longer you wait, the more the board is eaten.
  • Heat (near regulators, flyback) and time accelerate everything.

Diagnosis

  1. Visual: bulged top, brown/greenish leak, corrosion around the legs, film on the board, fishy smell (electrolyte).
  2. In-circuit ESR meter: reads without desoldering; an abnormally high ESR = dead cap. On PSU filtering, compare to neighbouring caps of the same value.
  3. On the scope: excessive ripple on a rail = tired filtering.
  4. Doubt: on a "known-recap" machine (MD2, GG…), do a full preventive recap.

Removal (the critical move)

SMD: never 'twist off'

Twisting an SMD cap to rip it out tears the pads and often the vias → a much longer repair. Use hot air (300-350 °C, flux) or two irons / one iron with lots of solder bridging both legs to heat them together.

  • Through-hole: add fresh solder, desoldering pump (or vacuum station on multilayer), finish with wick. Never force a stubborn cap → you rip the via.
  • Multilayer: internal planes sink the heat → preheat + vacuum station. Patience.

Cleaning (mandatory on a leak)

  1. Neutralise the electrolyte: it is conductive and corrosive. Isopropyl alcohol + brush, work under the old footprint.
  2. Stubborn leak: water + a little baking soda (neutralises the acid), alcohol rinse, dry (gentle hot air).
  3. Inspect corroded traces/vias under the microscope → repair before refitting (see traces & vias).

Refitting

  • Polarity: respect the − (stripe) / +; reversal = leak/explosion.
  • Value: same µF; voltage ≥ original (going up in voltage is fine). Don't raise the µF except on bulk filtering if space allows.
  • Quality: low-ESR, 105 °C, reputable series (Panasonic FR/FM, Nichicon, Rubycon). On hotspots, 105 °C is mandatory.
  • Polymer / MLCC replacement: at some points a polymer (or several MLCCs) gives far lower ESR and no leak — relevant for local filtering.

Tantalum and MLCC cases

  • Tantalum: polarised (mind the direction), never exceed the voltage (failure mode is a short → flames). Derate the voltage generously.
  • Ceramic MLCC: non-polarised, no leak; beware mechanical cracks (board flex) that create shorts.

After recap

  • Visual check (polarity, bridges), rail measurements, ripple on the scope.
  • Extended functional test (heat soak).

Kits & supply

  • Console5, RetroFixes, etc. offer per-machine cap kits (values pre-sorted) — handy so nothing is missed.

See also

Sources & attribution

  • Synthesis of established recap practice (retro/arcade); values = read off the board / cap kit, never invented.

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.