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Battery Acid Damage

This week I've had two machines come in; a Marshall JMP-1 and a Sequential Circuits Prophet 5 (yes, you read correctly). One was just in time and prior to battery leakage. Unfortunately the other arrived too late and had suffered considerable battery acid damage.

Last week I received a call from someone who had just bought a Marshall JMP-1 and, after stumbling across my article on Marshall JMP-1 Service while doing a little research on-line, decided to send me his new purchase for a once-over.

I got a shock, when I opened it as the battery was right on the point of popping. This was incredibly lucky. With a date of manufacture of 1992, the battery was the original, as fitted in Marshall factory, twenty-eight years ago!

Soldered CR2032 in Marshall JMP-1
Just about to pop, this CR2032 was fitted on to the main PCB of this JMP-1 at the Marshall factory in 1992.

After quickly removing the battery, I tried to take some macro pictures to show  swelling. If you look closely, you might be able to see what I'm talking about. The top of the battery should be flat.

Swollen CR2032 from Marshall JMP-1 (2020.12.15)
Look carefully and you'll notice the slight 'hump' on the top of the battery indicating that although this battery is still holding memory, it's also about to start leaking.

I analogise battery check-up with home security; most of us consider investing in CCTV or an alarm system after an incident! Stuart took the initiative and sent me his JMP-1 shortly after he bought it.

Unfortunately the owner of the Sequential Circuits Prophet 5 wasn't so lucky. Apparently this machine had been stored in a case since it was used with Roxy Music over thirty years ago.

A Sequential Circuits Prophet 5 last used over thirty years ago.
Last used over thirty years ago with Roxy Music, this Sequential Circuits Prophet 5 looks amazing.

It's incredibly sad to see horrendous battery acid damage on the inside of such a beautiful example of this legendary machine.

Battery Acid Damage in Prophet 5 2 (2020.12.16)
Inside the Prophet 5, what a mess!

Many components and quite a bit of PCB tracking are damaged but I'm going to try my best to fix this. Having said that, I've already informed the customer that things aren't looking good.

Battery Acid Damage in Prophet 5 (2020.12.15)
Components in the battery acid affected area have just rotted away. Some components just fell out of the machine as soon as I took off the bottom case.

So, I urge anyone who's buying vintage gear to get the memory back-up battery checked. I also strongly advise all, to regularly check the memory back-up battery in your equipment. Battery acid damage is a terrible thing and can cost a fortune to put right, if at all even possible.

My Live Forever battery mod which is available for most synthesisers, keyboards, effects processors, etc, doesn't just replace the factory fitted battery with something more substantial but if possible, I also move the battery off the main PCB.

Live Forever battery mod at Plasma Music
Large capacity CR123A battery mounted off-board.

Aurora (for the Roland MKS-80) and Super Nova (for the Roland Juno-106), are a couple of switched-mode power supplies that I make and that are either available ready assembled or can be installed by me. I recently released Aurora Board Bx, an option that includes a remote memory back-battery and Super Nova was designed with fully integrated remote memory back-battery facility.

Aurora Bx and Super Nova with on-board Live Forever
Both Aurora and Super Nova have an on-board Live Forever memory back-up battery facility.

I'm currently designing power supplies for several other machines and I'm including the same remote memory back-up battery facility on all of them.


Back-up batteries aren't just wired to memory chips. There's always associated circuitry which depending on the age of the machine, the manufacturer and so on, can do several jobs such as switch between battery and PSU power when the unit is switched on and off, provide current limiting and reverse polarity protection.

Memory back-up battery in the Marshall JMP-1 showing associated components.
As an example, here's a part of the Marshall JMP-1 schematic showing the memory back-up battery and associated circuitry.

Since my Live Forever battery mod connects directly to the original back-up battery connection points, any components or circuitry associated with the memory back-up function remain untouched and fully active. As far as your machine's concerned, nothing's changed!