The battery in your 1980s synth is on a clock
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If you own anything with a memory made between about 1978 and 1990, there is a battery inside it, and it was rated to last a few years.
Do the arithmetic. Most of these machines are on their first or second battery and are decades past the point where it should have been changed. Some of them are fine. A few are being eaten from the inside while they sit in the corner looking perfectly normal.
The useful thing to know is that "the battery" covers two completely different problems, and almost everything written about it online runs them together.
Problem one: the machine forgets
Most machines from the mid-eighties on use a lithium coin cell — usually a CR2032 or similar — to hold the patch memory when the power is off.
When one of these dies, the machine forgets. You turn it on and the patches are gone, or scrambled, or it has reverted to a set of factory sounds, or it will not boot past a memory error. Some machines display something helpful. Most just behave strangely.
This is annoying and it is not serious. Lithium primary cells very rarely leak in a way that damages anything. The board is fine. Replace the cell, reload the patches, carry on.
Machines that commonly turn up needing exactly this: Roland Juno-106, JX-3P, JX-10, Alpha Juno, Yamaha DX7, Korg Poly-800, Sequential Prophet-5, and the Casio CZ series — which, unusually, puts its batteries in a normal compartment on the outside, so you can change them yourself in a minute.
One thing to get right before you touch it. On most of these, disconnecting the battery instantly wipes every patch in the machine, and on some it takes the factory presets with it and they are not easy to get back. Save your sounds to a cartridge, a SysEx dump or whatever the machine supports before the battery comes out, not after. This is the single most common way people lose twenty years of their own programming.
Problem two: the machine dissolves
This is the one that matters.
A number of machines from the late seventies and early eighties used a rechargeable NiCd cell instead of a lithium one, trickle-charged by the instrument. Manufacturers largely stopped doing this in the early eighties, though a few carried on into the nineties.
NiCd cells leak. Not occasionally — as a matter of course, given enough decades. What comes out is corrosive, it is conductive, and it goes downhill onto whatever is beneath it. On a board where the battery sits above fine copper traces and sensitive components, the damage spreads outward from the battery and keeps going for as long as it is left there.
The famous case is the Korg Polysix, where the battery is soldered directly to the voice board. A Polysix that has never been touched has usually eaten part of that board. It is repairable — people rebuild them routinely — but the difference between a Polysix caught early and one left another five years is the difference between a straightforward job and a board rebuild.
Others that come up repeatedly on the same list: Korg Poly-61, Roland CR-78, Roland JP-4, Kawai SX-210 and SX-240, Teisco SX-400, ARP Chroma, and various Siel, PPG, GEM, Wersi and Peavey machines. Board layout is part of it — the CR-78 is a well-known example of a machine that was revised without moving the battery away from the thin traces next to it.
If you own one of these, this is not a "when I get round to it" job. Every month it sits there, it costs more to put right.
How to check without making it worse
You can do the first part yourself, and you should.
Look up your specific model and find out whether it uses a rechargeable cell or a lithium one. This one fact decides how urgent the whole thing is.
Then look at it. Unplug the machine from the wall first — not switched off, unplugged. Take the lid off, find the battery, and look at the board immediately around and below it. You are looking for white or green crust, a dull or discoloured patch on the board, or traces that look furry rather than clean. Photograph it.
Then stop. If there is any corrosion, put the lid back on and do not power it up again. Running a machine with active leakage on the board spreads the damage and can short things that were still fine. If it is clean, you have answered the question and you know where you stand.
We would far rather see a photograph of a board and tell you it is fine than see the same machine in two years.
What we do with them
Battery work on these machines is not really battery work. Fitting a new cell is ten minutes. The job is everything around it: neutralising and cleaning the residue, tracing where the corrosion has reached, repairing lifted or eaten traces, replacing components that have been sitting in it, and testing the sections that were downstream. On a machine that used a rechargeable cell, the charging circuit gets checked too, because there is no point fitting a new battery to a circuit that killed the last one.
And where the machine allows it, patches come off first.
Getting it looked at
Drop it in at Stockport, or post it in — we work with customers right across the UK. We are an authorised repair centre for AKAI, Numark, Denon DJ and Stanton, and we work on synthesizers, drum machines, samplers, mixers, mixing consoles, effects and outboard gear generally.
If you are posting a machine in, tell us the make, the model, and whether you have looked inside. A photograph of the board around the battery is worth a paragraph of description.
And if you only take one thing from this: go and find out, today, which type of cell is in your machine. That is a five-minute search, and for a few hundred people reading this it is the difference between a repair and a rebuild.
The Bench is an equipment repair workshop at Revelations House, Royal Oak Yard, Stockport SK1 1JZ.