Recap & Repair Reference

Aluminium electrolytic capacitors have a service life, not a permanent value. The electrolyte gradually escapes through the seal, capacitance falls and equivalent series resistance climbs, so a thirty-year-old board is running on parts well outside the specification it was designed around. The symptoms are rarely a clean failure: dim or shimmering video, hum or crackle on audio, intermittent resets and machines that work only once warm are all classic signs of capacitors that still measure roughly the right value on a cheap meter.

ESR is the measurement that matters

Capacitance alone will not condemn a capacitor. A part can read close to its printed value and still have an ESR many times its original figure, at which point it no longer filters anything useful. An ESR meter, used in circuit, sorts a board out in minutes. That said, on a machine you intend to keep running, replacing the lot is usually the better economy — the capacitors cost a few pounds and the labour is the same whether you fit five or twenty five.

Identify the board revision before you order

This is where recap jobs go wrong. Designators, values and even capacitor counts change between board revisions of the same machine, so a parts list for one assembly can be actively misleading on another. Find the revision marking on the PCB and match it to the guide before buying anything — that is why the lists here are organised by board rather than by machine name, and why each carries identification notes.

Practical cautions

Note the polarity of every part before removal and photograph the area; silkscreen markings are not always legible and are occasionally wrong. Leaked electrolyte is corrosive and conductive, so clean the pads and surrounding tracks properly and inspect for eaten vias rather than just fitting a new capacitor over the damage. Resist the urge to increase values: a larger capacitor can raise inrush current and upset timing in a supply that was designed around the original figure. Voltage rating may safely be increased, and often should be where the original was marginal. Where a board used tantalums — common on Amiga hardware — check what the guide specifies rather than assuming a like-for-like electrolytic is appropriate.

If the machine is faulty rather than merely tired, work through the hardware diagnostic flowcharts first — recapping a board with a genuine chip fault only hides the evidence. The capacitor code decoder will translate any markings you cannot read.