Author: sam

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Keyboard maintenance

My synth is dead – what can I do?

It’s a terrible feeling – to turn on your favorite synth, and instead of watching it gleefully come to life, you get…nothing.  No lights, no display, no sound.  Nothing.

It sounds like the worst problem a synth could have – nothing works!  But in reality, it could be a simple fix, if you are armed with a multimeter and a bit of sleuthing ability.

A multimeter may sound intimidating, but it’s an indispensable tool, not very expensive, and fairly easy to use.  But before we get to that, let’s take a look at what is likely causing your synthesizer to lie comatose.

If turning on your synth results in nothing coming on, the most likely causes are:

A blown fuse

A faulty or incorrect power adapter (if your synth uses this)

A bad wiring connection

A faulty power supply

All of these are pretty easy to check using a multimeter.  But to get to some things, you’ll need to open up your synth, and poke around where there will be potentially dangerous voltages.  So you’ll need to take some precautions, and if this sounds like it’s more than you are willing to handle, find a tech in your area who can do this job.  Read on, and you can at least have a better understanding of what he will be looking for.

Your friend, the multimeter

Ok, now about that multimeter…  It is such a handy tool that once you have one, you’ll wonder why you didn’t get it much earlier.  You can get a really cheap one at places like Harbor Freight, but spending a bit more (try eBay or Amazon) can get you a quality meter at a good price.  You basically want to be able to measure both AC and DC voltages, and have a ‘beeper’ to test the continuity of a circuit.  

Some multimeters do not have an audible continuity tester – make sure the one you get does.  With that tester selected, touching the two meter leads together will give you a nice beeeeep.  That nice synthy tone tells you that electricity can flow from one lead to the other, unimpeded.  When you touch those leads to the ends of a fuse, or a circuit trace, that reassuring beep will let you know that the electrons can travel as they should.

Test any external fuse

The first thing to check is any external fuse your synth might have.  With the synth unplugged from the wall, look on the back panel, where the power cord attaches, and if there is a fuse, remove it.  Set your meter to the continuity tester, and touch the leads to the opposite ends of the fuse.  If your meter is silent, then the fuse is blown.  Replace it with one of the same rating, and your work is probably done!

If the meter does beep, then the fuse is good, and it’s time to keep sleuthing.

Test the power adapter (if any)

If your synth uses an external power adapter (a ‘wall wart’, or a lumpy thing that plugs into the wall – something more than just a power cord), then it is possible that this has died.  Or perhaps you are using an incorrect power adapter. The label – probably with absurdly tiny text – should say what the Output voltage should be. It will say something like 9VDC (this means 9 volts DC).

Test the power adapter by plugging it into the wall, but not into the synth. Put the meter leads on the inside and the outside barrel of the connector, and measure the voltage there (set your meter to read either AC or DC voltage, depending on what the Output voltage of the adapter is supposed to be – most are DC). You should get a reading equal to or higher than the voltage specified on the adapter.

If you get no voltage, or a low voltage, it’s time to replace the power adapter.

If you are using a new power adapter on this synth – one that you have not used with it before – it’s possible it is still the wrong adapter, even if the voltage is ok. It might not have a high enough current rating (the tiny text on the adapter will specify this), or it could be the wrong polarity.

An adapter with a current rating higher than your synth requires is just fine. If your synth requires a 1A (amp) adapter, for example, and you are using one rated at 2A, that is no problem – you will have plenty of ‘headroom’. But if you are trying to use a 0.5A (or 500mA) adapter, it won’t deliver enough juice to power your synth.

The adapter should also show a diagram indicating the polarity, showing either the center pin marked ‘+’ and the outer barrel marked ‘-‘, or vice versa. This must match what your synth requires – and it hopefully has a similar diagram where the adapter plugs in. If the polarity of the adapter is wrong, at best, it won’t work. At worst, it could damage your synth.

(An adapter which delivers AC instead of DC voltage will not have a polarity.)

Check for a bad wiring connection

If you’ve made sure the fuse is okay, and any power adapter is working and correct, the next steps require opening up the keyboard. So this may be where some decide to hand off the task to a trained tech. After all, this is where you can be poking around dangerous voltages, and if your synth is still under warranty, it won’t be after you pop the hood.

So, if you continue, do so at your own risk, and be very careful.

Remove the power cord from the wall, and open up the synth. The first step is to simply give a good visual inspection. If you see any obvious signs of burning, you’ve likely found a good clue to the problem. But determining what caused the burning is more tricky, and the synth should probably be handed off to a tech at this point. A burned spot here could be caused by a shorted capacitor way over there, and it takes a lot of circuit tracing to find the culprit.

Another thing to scan for is loose wires. While it’s not common that wires simply come loose, if any did, they should be pretty easy to spot. A synth shouldn’t have any unconnected wires flopping around, so if you spot such a thing, it’s almost a sure sign of trouble. If a wiring harness came unplugged, and you are absolutely sure of where it should be plugged, then try reconnecting it and see if your synth comes back to life.

Sometimes a wire can break loose from a spade connector or from a solder joint, and if that has happened, it won’t be as obvious where the connection is supposed to be; for that repair, it’s probably best to take it to a service center where the tech can confirm – via the schematics – where the wire is supposed to connect, and then he or she can re-solder it.

Check the power supply

If you don’t notice any burned areas or dangling wires, it’s time to check the power supply. This is usually a circuit board inside the synth where the incoming power wires connect. If your synth uses a regular power cord, the internal wires will typically lead to a power switch and transformer, then on to the power supply board. If the synth uses a power adapter, there usually won’t be a transformer, just follow the wiring to the power supply board.

You may find some fuses here that are not accessible from outside the synth. Just as you did before, test these with your continuity tester – you can do this with the fuse still in place, but be sure the synth is not plugged into power! If a fuse is blown, replace it with the exact same type, and see if your synth is happy again. It very well could be a short-lived happiness, as whatever caused the fuse to blow in the first place may well cause it to blow again.

If no fuses are blown, try finding the service manual for your keyboard; with that, you can usually find out what voltages should be present at what point on the power supply. But tread carefully now – further testing requires turning on the power to the synth while you are poking around dangerous voltages! Don’t proceed unless you are confident of your abilities to measure live voltages!

With the schematics handy, switch your multimeter into DC Voltage mode, and test the points where the power supply should be delivering specific DC voltages. A common scenario is that some voltages are correct, but one is significantly lower than it should be, and that indicates that a section of the power supply has gone down.

That may seem like bad news, but the good news is that power supplies are fairly easy to repair, and they use common parts. So while you probably want to get it to a tech at this point, you can at least deliver it knowing that the problem is an easy fix, and won’t require sourcing any hard-to-find components.

The healing process

It could be that none of these things reveal any clues to your lifeless synth – there are many, many things that can go wrong in such a complex electronic instrument. But in most cases where the synth is lifeless, the issue is in the power supply or the parts that feed it.

Following your detective work, it may seem like most of the paths to healing your synth eventually involve handing it over to a repair tech. And while that is not nearly as satisfying as bringing it back to life all on your own, techs charge an hourly ‘bench rate’, and the more you can reduce the time they spend tracking down the problem, the more money you will save on the repair bill.

But perhaps more importantly, your journey down the wires of your synthesizer is a great education, and whatever familiarity you gain with this synth will be a great background for the next keyboard problem you tackle!

Categories
Keyboard maintenance

My synthesizer needs a new main board!

The heart and soul of a synthesizer is its main board, the place where the nitty-gritty happens, where the most basic and the most important functions take place. If your synth turns on but the display shows weirdness, or if it boots up but gets stuck on one screen, or freezes up in the middle of your song, these are the sorts of things that can indicate that the main board – sometimes called the mother board – is faulty.

Repairing a non-working main board is not for the faint of heart. It requires an experienced tech with diagnostic tools to determine that this one chip amongst hundreds has failed, or that the ROM has been scrambled, or that pin 27 of the CPU chip isn’t receiving the correct reset voltage. It’s a process that takes many hours of bench time at expensive hourly rates.

If your main board has gone off to PCB heaven (PCB stands for printed circuit board), it is often quicker and cheaper to simply replace it. That process usually involves simply removing the old board (often as simple as unplugging wiring harnesses and unscrewing the board) and dropping in a new one. The hardest part of the equation is often finding a replacement circuit board. What do you do when your beloved SonoSlapper 6000 needs a new main board, and a Google search turns up no results?

At Syntaur, we’ve been having good luck finding main boards for lots of fairly recent instruments – meaning those of this millennium – simply by developing good relationships with the manufacturers. If there is a brand new main board out there, we can usually find it. Ok, we might not be able to find that mother board for the SonoSlapper 6000, but if you have a Korg Krome, or a Nord Stage, or especially a Yamaha synth or digital piano that needs a heart transplant, we can probably help.

Yamaha, in particular, makes so many different keyboard models that we’re always racing to keep up. At the time of this writing, we list parts for 630 different Yamaha models, and there are at least that many that we haven’t gotten to yet! So if you need a board for a Yamaha CLP or CVP Clavinova digital piano, or a Yamaha PSR portable keyboard, or a Yamaha stage piano or synthesizer, it may indeed be available even though the internet seemingly offers no hope. Yamaha is a huge company, and is probably the best for maintaining a parts inventory for their keyboards. And if they have a replacement main board tucked away somewhere, we can get it for you.

The trick is to not get dismayed by the fact that we may list a hundred parts for your synth on syntaur.com, but no main board. In that instance, let us know you need this board, and we’ll go on the hunt. At the bottom right of nearly every page on the site, you’ll see this link: ‘Can’t find the part you’re looking for? Make a request for it here.‘ Once we see your request, we can find out if the board is still available, and if it is, we’ll let you know how to special order it.

Even if the circuit board is out of production and not available from the manufacturer, all is not lost. We have an absurd number – hundreds and hundreds – of synthesizers in line to be either refurbished or scavenged for working parts, so we can also check our database to see if perhaps the synth model you need to repair is lurking in our warehouse. If so, we can test it to see if the main board is good.

Long story short: We’re happy to do a bit of research to see if we can find a main board for you. After all, we live to bring old synthesizers back to life! But I ask just one favor: Please don’t call to ask us this – use the website form mentioned above. That gives us a record of who is looking for what, and it makes it easy for us to do methodical checking. Otherwise, your request will get scribbled on a slip of paper, which then gets moved to someone’s desk, and then faces an uncertain future. My desk, for example, is arranged in archeological layers. Trust me – you don’t want your main board request to land there.

We often think these days that if Google can’t find something, it’s not to be found. But we’ve still got some tricks up our sleeves.

Categories
Keyboard maintenance

Keys not responding correctly? Check the contact strips.

One of the most common problems with electronic keyboards is keys that don’t respond the way they should. Perhaps one or more notes don’t sound at all, or a note plays sporadically. Or the most telling symptom: a note that always plays at full volume no matter how hard you press the key.

These are all symptoms of dirty or worn out contact strips, the rubber strips that span the keyboard on most synthesizers. And the good news is that repairing these issues is not difficult, not very expensive, and is a great first project for anyone wanting to try their skills at synth repair.

To determine if you have bad contact strips, play chromatically up the keyboard and see:

(1) if specific notes don’t play at all

(2) if specific notes play only at full volume

If you find either symptom, it’s time to clean or replace the rubber contact strips.

What the contact strips do

The contact strips are the interface between the plastic keys and the electronics that make the sound. Somehow, the synth has to tell the sound circuitry what notes to play, when to play them, and how loud each of them should be.

The contact strips do this by means of a rubber “bubble” underneath each key. And inside each bubble is a carbon pad – and that carbon conducts electricity. So when you press down on a key, the key presses down on the bubble, and that carbon pad presses against a circuit board (the key contact board) and completes the electrical circuit. All of this tells the sound engine, “Play note D#5” for example.

Now, how does the synth know to play loudly when you play harder, and softly when you play softer? It does this by using double bubbles! (Sounds like a chewing gum ad…) Each bubble in the contact strip has two carbon pads in it, at slightly different heights. So when you press down on a key, one contact is made slightly before the other. The synth measures the time from the first contact to the second, and it translates this to key velocity – which is then translated to how loudly a note is played.

Some modern keyboards – mostly digital pianos – have three contacts per bubble, for even more responsive velocity sensitivity.

When things go bad…

There are two sources of trouble for contact strips. First of all, they can get dirty. If a drink is spilled into the keyboard, or a bit of grit gets between the contact strip and the key contact board, the proper contact won’t be made, and they key won’t respond as it should.

The other source of trouble is that after a lot of use, the carbon contacts just wear out. The black carbon dots inside the contact strip should have a matte finish, but as they wear, they get more of a glazed, shiny look, and will even show the pattern of the contact surface from the circuit board.

What to do to fix the problem

You’ll need to get the keybed out, and remove the contact strips. This usually only requires not much more than a screwdriver, and unplugging a cable or two. If you can find the service manual for your keyboard online, it can big a big help in the disassembly.

Once the keybed is out, remove what you need to get to the contact circuit boards underneath the keys. The contact strips are attached to these boards, usually via rubber nubs on the strips which fit into holes on the circuit board.

Often, you can leave the keybed plugged in, turn on the keyboard (be careful not to touch any exposed wiring, especially around the power supply!), and you can press a bubble down with your finger, “playing” that note.

So find the notes that don’t work as they should and pull that contact strip up gently from the circuit board. As you pull, the rubber nubs should come out of the circuit board holes, but you may need to help them along – you don’t want to tear the rubber strip. You can push from the opposite side with a toothpick to help release each nub.

Usually the strips are in octave sections, so you might only need to remove one or two of them. Once a strip is off, take a look at the underside, and see if the carbon surfaces looks glazed. If so, you may want to replace that strip (or all of them, if you’re the proactive sort). If the strip is noticeably dirty, you can wash it in warm water with dish soap.

Likewise, go ahead and clean the contact areas on the circuit board also. Use a Q-tip and 70% rubbing alcohol to swab each contact point.

Once everything is cleaned up, put it back together enough to see if the errant notes work now.

If you still have trouble with a particular note, try swapping that contact strip with another, to see if the problem moves to the new place on the keyboard, or stays on the same note. If it moves with the contact strip, you’ll want to replace that strip. If it stays on the same note, the problem is with the contact board – it’s either still dirty, or it may need repair or replacing.

Installing contact strips

Whether you are replacing a strip with a new one or reinstalling strips that you removed and washed, be aware that some types of strips are a bit too symmetrical – in other words, it is possible to install them backwards. If yours fit only one way, then great – there’s nothing to worry about. But if you can flip it around 180 degrees and it still fits onto the contact circuit board, take a minute and make sure you get it on the correct way.

Remember those “double bubble” strips which have the carbon contacts at two slightly different heights? The keyboard scanner circuit is waiting for the lower contact to hit first, so it can then measure how long it takes the higher contact to hit, and thus tell a note how loudly to play. If the strip is put in reversed, the circuit thinks the two contacts strike at the same time, and it sends the message, “Maximum velocity!” So if you reassemble everything, and you have an octave of notes that all play at maximum velocity, you can be certain that you’ve installed a contact strip backwards.

Key contact board issues

If you have tried everything above, and still have a problem with one particular note, then it’s likely a faulty key contact board. A soda spilled into the keybed can cause circuit board traces to eventually corrode, and this can lead to one or more notes going silent. Cat pee is another terrible fate for a contact board.

Depending on where the damage happened, you might lose either a contiguous grouping of several notes, or you could lose a repeating pattern of notes, such as every F across the keybed, or every 8th note as you play chromatically.

In these instances, your options are either to repair or replace that key contact board, and replacing it is by far the easiest. These boards are not very expensive, and there is a good chance that the one you need is available. Syntaur is likely to have the contact boards and the contact strips available for your keyboard.

If not, you’ll probably need to take your board to a repair tech who can test the traces and make any necessary repairs to them. (This will almost certainly be more expensive than replacing the board, so it’s a last resort.)

Reassemble, and make some music!

Now it’s time to put it all back together, and enjoy being able to play any note you desire – and bask in the pride of having repaired your own keyboard!

Categories
Keyboard maintenance

How to tell if your Juno-106 needs voice chips

juno-106 synthesizer

It’s no secret that the Roland Juno-106 is a great analog synth – and that the proprietary voice chips are it’s Achilles heel.  These chips – one for each of the Juno’s six voices – were dipped in an epoxy coating when they were made back in the early 1980’s.  And decades later, it turns out that that epoxy starts becoming conductive as it ages.  A conductive coating on an electrical circuit = Not Good.

The fix is pretty straightforward, though you’ll want an experienced tech to handle the repair.  Because the problem is so common, Analogue Renaissance has remanufactured the voice chips with bullet-proof modern components, and their voice chips sound exactly like the originals.  You can purchase these from Syntaur here.  But installing them requires fluency with soldering – and especially with de-soldering.  It’s easy to get the circuit board too hot, and lift the delicate traces, causing even more trouble with your Juno.

But the first step is determining whether or not you need to replace voice chips – after all, each voice chip will cost about $60, plus the cost of installation.  (If you buy a complete set of six chips, you’ll get a discounted price.)  So it’s not cheap –  but it will certainly up the value of this classic synthesizer.

To determine whether your Juno-106 needs one or more voice chips, you will:

Boot up in test mode

Play notes, and see in the display which voice is sounding

Take note of any voices which sound irregular

Set the filter to self-oscillate, and check the individual voices again

Take note of any voices which sound irregular

Here are the details for doing each of these steps:

Boot Up in Test Mode

Power on the Juno-106 while holding down the KEY TRANSPOSE button; this will put the synthesizer in Test Mode. The display will read ‘-_’. Press the POLY 1 and POLY 2 buttons together, and now for each note played, the display will show which voice is sounding (‘-1’ through ‘-6’).

You may want to give the Juno five or ten minutes to warm up before you start getting serious about listening to voices.  It’s an analog synth, and it needs electrons flowing through those circuits for a while before it settles down and gets stable.  It’s no problem to play it during this warm-up period, it just may sound a bit goofy.

Play notes, and see in the display which voice is sounding

Play one note at a time, and the display will indicate which voice is sounding; the Juno will cycle through the voices consecutively.  So pressing a key repeatedly, for instance, will show -2, -3, -4, -5, -6, -1, -2, etc. in the display.  

Take note of any voices which sound irregular

If a voice sounds goofy while you are doing this, make a note of which voice it is.  If you hear a crackling sound every time voice 4 plays, you know that voice 4 likely needs a new voice chip.  Other tell-tale signs of a failed chip are voices that sound very thin, or distorted, that hang on after the key is released, or that don’t sound at all.

If a voice sounds just slightly askew, it may just need a calibration.  If the voice sounds out of tune, or a bit dark, for instance, that can be corrected by calibrating the Juno (the subject of an upcoming post).  Crackly, distorted, or hanging notes, on the other hand, are the indicators of a bad voice chip.

Set the filter to self-oscillate, and check the individual voices again

This is my favorite trick for finding bad voice chips – it works to ferret out a bad chip that sounds normal under most circumstances.  The idea is to turn off the oscillators completely (including the sub-oscillator), then make the filter self-oscillate – which means it will ‘play’ a sine wave.  Often, a faulty voice chip will lose this ability to self-oscillate.

To set this up, turn the pulse and sawtooth off, and set the SUB and NOISE sliders all the way down. Now, make the filter self-oscillate by setting the RES slider fully on – you should now hear a sine wave sound, and the FREQ slider will control its pitch. Set the VFC ENV and LFO sliders all the way down, and with the VCF KYBD slider fully upward (this opens the filter to match the keyboard tracking), the filter should play chromatically as you play the keys.

Take note of any voices which sound irregular

As you play notes with the filter self-oscillating, if a note doesn’t sound at all, that almost certainly indicates a failed voice chip.  So take note of the display when a voice doesn’t play, and like before, it will tell you the voice number which is bad.  If a note plays, but it noticeably out of tune, that’s another indicator that your Juno just needs a good calibration.

Now, you should be fully informed of exactly how many voice chips you need, and exactly which voices need them – in other words, which specific chips on the PCB need replacing.  

If you find that you need multiple voice chips, you might consider replacing all of them – if several have gone bad, then the others might not be far behind.  And your Juno-106 is a good investment – replacing all of the voice chips will ‘future-proof’ it, which will make it an even more valuable instrument!