Fixing common problems with your ancient junky keyboard (Part 2): The battery

Mar 22, 2006 04:45

You are now understandably anxious to get into the sounds of the mid-80's. I don't blame you; these instruments will open up vast new vistas of electronic politeness. Before you start seriously using your new (to you) synth, though, it would be smart to do some preventative maintenance.

Or redemptive maintenance, if necessary.

First thing to do is plug the synth in to power and amplification and turn it on. Does it turn on? Does it load its operating system? Does it say "Sequential Vector Synthesizer"? Well, probably something more like "Roland Digital Linear Transwave Synthesizer". Does it say "Battery Low"? When fully booted up, your screen should display some patch name (i.e. "Digital Clav"). Note down anything like OS version numbers, low battery warnings and other messages your synth displays during bootup.

Start playing the keyboard. If it doesn't sound, keep holding the key for a few more seconds. Do you hear a kind of rumbling white noise? If you do hear sound, switch to the user-definable patches. Are there any there?

Oh, enough with this charade. Unless you know when the battery was last replaced (and that time was in the last few years), you need a new synth-battery!

A little background: every mid-80's synth is basically an 8-bit computer specifically programmed for music and with a piano-type interface. It stores patches in its RAM and that RAM needs to be supplied with power constantly to maintain its state. This is supplied by very long-lived lithium batteries. I've seen these batteries last almost 20 years, but their advertised lifetime is less than 10 years. When these batteries go out, the patches disappear and all values are replaced by zeroes or random data. The sound of all zeroes (say, in the case of the Sequential Multitrak) is sometimes a slow noise sweep but is usually silence.

Starting from the top (literally), remove the cover of your synth. Don't worry; the warranty expired before you entered middle school. Here are the simple steps for most synths of this era:
1. Ground yourself by touching the metal case of some plugged-in electronics or by touching a water pipe. This will discharge what static you might have built up.
2. Unplug the synth (if it is plugged in).
3. Remove the screws holding the top panel on.
4. Flip up the top panel. If your synth is cool, it will have hinges at the back. If it is slightly less cool, you'll have to detach it and rest it in an upright position so that no ribbon cables become disconnected.
5. Detach any obstructing ribbon cables. Mark the base of the board near where the red or black "key" wire in the ribbon cable attaches so you can recall the cable's orientation.

Now look for the battery. It is usually somewhere on one of the synth's logic boards (near the RAM). If it is a flat and wide pancake shape (Alesis MMT-8, HR-16), then it is a 3.6 V lithium. If it is coin-sized and silver then it is also a lithium battery (Korg Poly-800, Roland D110). If it is cylindrical and looks like a large capacitor, it is yet again a lithium. If it looks like a pile of lithium coin batteries shrinkwrapped in colored plastic, then it is a NiCd.

NiCd batteries, unfortunately, are prone to leak after they expire. If there is fuzzy bluish liquid near the base of the battery, it has died and is leaking acid onto the circuit board. Clean off what acid you can find and quickly desolder the battery from the board. Hopefully, none of the circuit board traces were affected. If they were (look for discoloration, oxidation, swelling under the plastic coating), you'll need to replace them by routing wires. Here is a guide on how to perform this procedure on a Korg Polysix: http://www.oldcrows.net/~oldcrow/synth/korg/polysix/repair3.html

Fortunately, most synths I've seen newer than the Polysix or the Prophet 600 use lithium batteries. As an aside, old Amiga gear used NiCd batteries for clock chips, resulting in all kinds of reliability problems.

Despite the age of the hardware, all of the batteries you will run across are still in production and will be easy to replace. Lithium coin batteries can be found at any Radioshack and many large stores. Larger lithium batteries can be found at specialized electronics stores (in the PDX area is Norvac in Beaverton) and from large electronic cataloges. Always get batteries with leads attached that match the ones in your instrument. Expect to pay from $2 (small lithium coin) - $10 (large lithium cylinder) for new ones. They're terribly cheap considering the amount of usability you get and compared with the cost of getting a professional to swap your battery.

If you haven't soldered before, then maybe it would be good to get a professional to swap your battery. And also: don't use a soldering gun or anything that could fix plumbing. A nice (as in good quality) 15-25 W soldering iron would do just fine.

The hardest swap oddly enough is with the coin-like lithium battery in the Korg Poly-800. That thing is soldered directly into the board. It was almost like Korg didn't expect people to still be rocking the "Underwater Strings" 20 years on. To replace the battery, I soldered wires to the top and bottom of the battery and ran those to the board. Not pretty but fairly solid.

Coin-like lithiums usually pop into holders, which is nice.

Replacing large cylindrical lithium batteries is more involved, but not hard. They come in two flavors; with posts soldered into holes in the board, and with tabs that solder into solder "pads" on the board. Making one fit with the other will take a bit of doing, so try to order the right one. For those with posts, first heat one side of the battery posts with the iron and gently work that side of the battery free. Repeat with the other side and remove battery. You shouldn't have to take out the circuit board to do this procedure. Next, tin the leads of the new battery and insert it into the vacant holes. MAKE SURE IT IS NOT BACKWARDS. Apply iron and a small amount of solder to each hole until battery is securely soldered into place. For tabs, heat the first pad on the board with the iron until the solder is melted. This will sometimes take a gentle back-and-forth action across the pad to make sure your iron is heating the pad evenly. When the solder is molten, carefully lift one edge of the battery until its tab is free. Repeat with the other and remove the battery. Tin the tabs of the new battery and place the tabs on the pads. MAKE SURE IT IS NOT BACKWARDS. Heat the tabs and immerse them in the molten metal of the solder pads.

I've never replaced a NiCd battery; I've only removed them. The procedure should be the same, but they should be replacable with lithiums.

Your synth should now have energy and spritelyness! It should have memory and diction. It should feel 10 years younger! Close the case and try it out, but don't screw it back together. We still have more work to do!

Next up is Part 3: Keys, buttons, switches
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