Batteries are great things, they start your car in the morning, they are in the emergency torch that you need if the lights go out, your mobile phone wouldn’t be mobile without them, and the list goes on…
But their story in Synths is very much a mixed experience, for the most part they back up your editing and work, so when you call up your killer preset on stage it will be exactly what you meant it to be, and for the most part this is true. But perhaps for inhabitants of the 21’st century some of the unforeseen issues of the past battery technologies are starting to rear their ugly heads.
There seem to be two types of batteries that cause damage in Synths and other Electromusic products, rechargeable Ni-Cad’s and dry cell batteries (the kind you would put in a torch).
Large cylindrical dry cell batteries were used in a few Pro synths such as the SH101 and the Poly 800, so they could be played portably on stage, and as memory backup for some Drum Machines such as the TR808 and 909. A lot of home keyboards by Casio, Yamaha and others had them as well but any bad consequences of leaky batteries in these have probably led to Land-Fill many years ago, thankfully we all recycle now.
Currently the SH101 has achieved quite a high value, and the Poly 800 is only a couple of hundred of your currency behind but an incredible amount of damage can and has been done by leaving a full set of Alkaline or Zinc Chloride batteries in one of these for a few years. Whether the damage is terminal or not depends on the physical attitude of the synth in storage, is the synth stored on it’s back or on one of it’s ends, or flat (as in a playable position) or upside down in a box?
From our experience, the position that assures it’s possible resurrection is flat on it’s back, in the playable position, any of the others is probably terminal, but not leaving any dry cell batteries in these machines long term is definitely the safest option. You might lose the onboard presets in an early Mk1 Poly 800 or your sequence data in your SH101, but it is a small price to pay in the end.
The above image is of the metal base plate of an SH101, the other end of this part was just as bad, and the output jack board had to be completely stripped and rebuilt and many components replaced, in order to make this synth any way reliable. The battery terminals themselves had to be replaced and a tremendous amount of cleaning had to be done to remove the legacy of battery acid from the inside of the synth. This one was stored in the playable position, can you imagine how bad it would be if it had been otherwise?
We have the carcass of a Poly 800 here, it was stored upright with the joystick side on the ground, the battery acid had eaten through parts of all the connectors that link the front panel and the main board, but had also managed to eat through a lot of the PSU circuitry and the relevent unobtainable connectors. Even the filter chip in it’s socket had a lovely green patina on every pin and cannot be assumed to be a survivor. The front panel board and the Chorus board seemed to survive intact as they were away from the direction of the batteries leaking and they look fine. They will do for spares.
The other major source of damage to older synths is the Nickel Cadmium rechargeable batteries (NI-Cads) that are commonly thought to be only in a few synths but that list seems to be growing. The original idea was that a battery that was trickle charged when the synth was switched on would never need replacing. and this theory was good for about 15 years before they started to decompose into their constituent chemicals and start to leak a corrosive cocktail all over the PCB. As this is always the main CPU for the synth, this is going to lead to major problems. Originally the Korg Polysix was the most infamous for this, but the Korg Trident 1 and 2 both have them, the Korg Poly 61 is another, and the list also includes the OSCar, the PPG Waves, the Siel Opera 6 and recently the GEM S2/S3 Turbo, and there are probably many more. We have a Lexicon M200 Reverb unit which was also almost destroyed by a Ni-Cad battery in it. The Lexicon truly didn’t need to have a Ni-Cad in it, it only has 2k of lower power RAM in it, and a Lithium Ion battery would easily have supplied it’s needs for 20 years or more.
The picture below is of a Korg Polysix which had the luckiest escape from Ni-Cad disaster that we have ever seen, it was stored in the Polysixes sweetspot, upright and on it’s back, the rear panel towards the floor.
The corrosive compounds leaked directly from the battery to the rear chassis just avoiding the power supply and only spattering the cables and connectors on that end of the CPU board.
This is rear panel after cleaning, all of the connectors were stripped down, checked, repaired and rebuilt and the back panel is about as good as we can make it. All in all, a remarkable escape.
The above picture is part of the interior of a Lexicon M200 Reverberation unit and shows all of the circuitry related to the power on reset, muting and control panel interrupt timing. The RAM chip is at the top right of the picture and this is also tied into this block of circuitry as only after a successful reset will the RAM be enabled.
When acid starts leaking onto a pcb, it eats into the Lead and the Tin of the solder joints, Oxidising them and making them very reluctant to accept heat from a soldering iron and to thus melt. It turns even cutting out all the damaged components and trying to clear their pin holes extraordinarily difficult. Just cutting out the components and clearing the component holes took more than 3 hours, and this took a lot of heat, liquid solder flux and patience to do.
The above picture is after everything was replaced, the Lithium Ion battery now backs up the RAM and the diode resistor combo at the right centre of the picture is to stop the Lexicon trying to recharge the Li-on battery.
The 2 IC’s to the left of the picture both had to be replaced and the the Z80 main CPU had also gone faulty probably as a result of the battery damage.