Repair guide

Remove a leaking Amiga clock battery and clean the board

Old clock batteries on Amiga boards are known to leak and eat traces, so the safest repair is to take the battery off the board entirely and clean up. This guide covers removing it, cleaning the damage, checking traces and fitting a replacement that cannot leak onto the board.

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Battery · Careful · about 90 minutes. Worth doing. Reports say this fix helps on many machines.

You are in the right place if: The Amiga forgets the date, or you can see green or white crust and tarnished solder near the old battery.

Before you start

Leaked battery residue can burn skin and eyes. Wear gloves and safety glasses and work with ventilation.
Do not recharge or short a leaking cell, and dispose of it as battery waste, not in household rubbish.
Some boards trickle charge the battery. If you swap a rechargeable for a non-rechargeable cell, look up how others on your exact revision handled the charge path before you power it on.
If traces to several chips are eaten away, or you are not comfortable with fine soldering, stop and send it to a repair person rather than guessing.

Board revisions and models

Battery type, location and charge circuit differ between the A500 (on the trapdoor expansion), A600, A1200, A2000, A3000 and A4000. Confirm your board revision before you follow any specific modification.

Parts you may need

Coin cell or battery holder. An off-board or socketed cell is easier to swap and keeps any leak away from traces Amazon · eBay
Thin jumper wire. For repairing broken traces Amazon · eBay
Replacement cell. Only if your board revision still expects a rechargeable cell Amazon · eBay
White vinegar and 99% isopropyl alcohol. Neutralise then clean Amazon · eBay

Tools

Soldering iron and desoldering braid. Remove the battery and clear holes Amazon · eBay
Soft brush and swabs. Scrub off residue Amazon · eBay
Magnifier or microscope. Look at traces and via damage Amazon · eBay
Multimeter. Check repaired traces Amazon · eBay
Nitrile gloves and safety glasses. Leak residue irritates skin and eyes Amazon · eBay

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Step by step

Power down and open up Unplug the machine, discharge yourself on a metal case and open it. Keep the screws in labelled piles.
Find the battery Locate the clock battery. Depending on the model it may be a barrel cell or coin cell on the board, or on the trapdoor RAM expansion on an A500. Photograph it from several angles first.
Note polarity and the surroundings Mark which leg is positive on your photo, and look at what sits next to the battery: traces, chips and sockets are the usual victims of a leak.
Look for leak damage Check for crust, discolouration, lifted solder mask and green copper. If you see any, plan to clean thoroughly before anything else.
Take the battery off Cut the battery body free from its legs if it is stuck, then desolder each leg and clear the holes with braid or a pump. Do not pry a soldered battery off with force.
Neutralise and clean With gloves and eye protection, neutralise the residue (a mild acid such as white vinegar on a swab for an alkaline leak), then scrub with isopropyl alcohol and a soft brush until nothing sticky is left. Dry the board fully.
Inspect and repair traces Under magnification, check every trace and via around the old battery. Fix any broken track with a thin jumper wire, and check continuity to the nearest chip pin.
Fit a safer replacement Fit a holder or a lead to an off-board cell so that a future leak cannot reach the board. Match polarity and check the board revision for how the charge path was handled (see cautions).
Test and set the clock Reassemble, power up, set the time in Workbench, then power off for a few minutes and check it keeps time.
Check for hidden damage If the machine misbehaves after the clean-up, check nearby sockets and chips for corrosion before blaming other parts.

Tips, tales and maybes

Found in write-ups and forum threads. These are other people's reports, not tested by us.

Tip (Medium confidence). One A500 owner on a mailing list pointed at the trapdoor battery, not the capacitors, as the headline fault on that model. Source
Story (Medium confidence). A battery-leak repair on a newly acquired A2000 is shown on video, including cleaning and a recap afterwards. Source
Watch out (Medium confidence). An A1200 black screen turned out to be reversed capacitors from an earlier repair plus a broken trace, so double-check polarity after any battery or recap work. Source

Guides we used

We wrote the steps in our own words from these. They have the photos and the full detail, so please read them and support their authors.

cctalk post on the A500 trapdoor battery (Forum) by classiccmp mailing list. A list post saying the A500's headline failure is the battery on the trapdoor expansion, not the electrolytics.
Jan Beta's Amiga 2000 Battery Leakage Repair and Recapping (Video) by Jan Beta (YouTube), listed on The Oasis BBS. Video of a newly acquired A2000 with a battery leak plus a recap; useful to see what a leak looks like on the board.
Why recapping isn't always the cure (Amiga 1200 repair story) (Blog) by LinuxJedi. An A1200 black-screen case caused by reversed capacitors from an earlier repair, a bad Paula chip and a broken trace; a good reminder to check polarity and traces.
Recapping Amiga computers (Blog) by walkero.gr. A walk through an Amiga recapping job.

Boards and models vary, so check what is in front of you. A repair can involve hot tools, chemicals and, on some machines, dangerous voltages. You do it at your own risk.