Yamaha SY85 Battery Replacement Guide


The Yamaha SY85 has an internal 3 Volt Lithium battery that keeps all the synthesizer settings, patches, performances and sequence memory intact when the unit is powered off. It also supplies standby power to any SYEMB06 memory modules you may have installed.

If the battery voltage is low you could lose all your internal settings!
A number of unusual problems may also appear when you use the SY85. Be aware that an exhausted battery may leak and cause damage to the PCB and surrounding components.

The SY85 checks the internal battery voltage at power-on.
If the SY85 LCD displays this message at power-on you must replace the battery:

You can manually check the battery voltage by switching the unit on and pressing this button sequence below to bring you into the diagnostics menu:
[SHIFT] + [STORE] + [EXIT / NO] all held down in that sequence.

When you enter the diagnostics menu a message similar to this will appear:

After a few seconds the display will switch to the menu mode and will display these options:

To check the battery voltage press the panel buttons in this sequence:
[+1] then [PAGE >] then [PAGE >] then [ENTER / YES]

The display will show the battery voltage screen:

If your voltage is less than 3.0V you should think about changing the battery soon.

To exit out of the diagnostics menu press this sequence of buttons:
[EXIT / NO] then [+1]

The SY85 will now re-boot like it does at power-on.

Battery Change Preparation

Changing the internal battery involves opening the SY85 and removing the main PCB.

The SY85 will lose all its internal data during this procedure.
If you have anything important in there you need to back it up now. This includes voices, performances, sequences, synthesizer settings, and any samples stored in SYEMB06 modules.

After the procedure you will need to restore all the internal settings to default using the Factory Set Disk supplied with the SY85.

Points to consider BEFORE proceeding with this battery change procedure:
1. If you have no experience of soldering PCB components DO NOT CONTINUE.
2. If you are thinking about doing this without the anti-static strap or workbench DO NOT CONTINUE.
3. I am NOT responsible for any damage you do to your SY85. THIS IS AT YOUR OWN RISK.

The battery type fitted in the SY85 is a CR2450 with solder tags. Instead of replacing it with another solder tag battery you can use a CR2450 battery holder with a standard CR2450 cell. If you ever need to replace the battery again you do not need to remove the PCB or unsolder anything.
Note: The battery holder I used had a leg pitch of 20mm.

Items you will need to perform the battery change procedure:
• Yamaha SY85 Factory Set Disk
• Anti-static wrist strap to ground yourself to an earth point.
• Work bench with anti-static grounded mat for PCB work.
• Soldering Iron.
• Solder removal braid to suck the solder out of the PCB holes.
• Philips ‘star-head’ screwdriver.
• CR2450 3 Volt Lithium cell.
• CR2450 battery holder with leg pitch of 20mm
• Digital Multimeter if available to check battery voltage after installation.

Remove the Motherboard PCB

Remove any Wave or Voice cards from the slots on the top of the unit and place the unit face down on soft material to prevent scratches

Remove all the screws from the bottom cover except the screws marked in YELLOW.
There are two screw sizes used to keep the cover on. The screws marked in CYAN are the larger of the two sizes.

Cover Screws:
There are 11 large screws and 27 small screws.

Now lift the bottom cover off to expose the SY85 internals:
The white arrow points to the battery location at the top right of the main PCB.

Before touching anything inside the SY85 you need to use the anti-static grounding strap.
Connect the strap’s croc clip to an electricial earth point

Remove any Sample Memory Expansion Boards:
Now would be a good time to remove any SIMM or SYEMB06 expansion boards and place them in a static safe area for now.

Isolate the battery from the rest of the PCB circuitry by removing the Jumper CP1 from the two jumper pins.
You can place the jumper on just one pin of CP1 to prevent losing it as shown in the pop-out photo below:

Carefully remove the four cable plugs out from the PCB left side connectors:

Connector CN12 is a tricky one!
You need to release the cable by lifting up the outside part of the connector first.
Carefully ease the cable out of the connector – patience needed here as it may not come out easily!

Remove the three Front Left Connectors:

Remove the two Front Right Connectors:

Remove the two Right Side Connectors:

Now remove the nine screws holding the PCB in place.
The rear of the PCB uses six coarse thread screws.
The front of the PCB uses three fine thread screws.

PCB Left Side Screws:
5 coarse screws at rear, 1 fine screw with metal cable tie at front left:

PCB Right Side Screws:
1 coarse screw at the right rear, 2 fine screws at the front:

This is the location pattern of the screws holding the PCB in place:

Once you have all the connectors and screws removed from the PCB tuck the cables under the PCB as shown below:

Tilt the PCB up and pull it forward and out away from the rear of the unit:

Place the PCB on a static safe area or workbench:

Battery Removal and Installation of Battery Holder

The factory installed solder tag battery has three pins:
One pin on the Negative tag and Two pins on the Positive tag.

The easiest way to remove the battery is to target the single pin Negative tag first.
Once you have that pin out of the PCB the two Positive tag pins can be worked a little at a time until the battery eventually falls out.

Note: The battery Negative tag pin is soldered into two large copper planes on the top and bottom side of the PCB.
This has the effect of sinking the heat from the soldering iron so you need to be patient when removing this pin.

Let the solder on the pin melt fully before working at the pin.

Hold the iron to the Negative pin (right photo) and with gentle pressure lever the battery down so the pin is worked out of the PCB.

With the Negative pin now fully out of the PCB it’s time to target the two Positive pins.

Target each pin in turn.
Heat the pin and gently tilt the battery away from it
Keep alternating between pins until the battery finally falls out of the PCB.

With the battery out of the PCB use the solder braid to pull the solder out of the Negative pin hole and the right-side Positive hole.
We don’t need the left-side Positive hole for our battery holder so tidy any solder spikes or balls that may have formed when the battery fell out.

You may have to clear the Negative hole with the braid from both sides if the large copper planes prevent the solder from coming out fully from the PCB bottom side.

Now that the PCB holes are clear of solder the CR2450 battery holder can now be fitted.
Fit the center Negative pin of the battery holder to the large copper plane hole.
Fit the outside Positive pin to the front right PCB hole.

Make sure the battery holder is flat on the PCB.
Flip the board over and solder the battery holder pins whilst keeping the battery holder flat to the PCB.

Now that the battery holder is soldered in place you can put the new CR2450 battery in!
Depending on the design of the battery holder there is a possibility that the battery may short-out for a split second against the retaining clip as you push it in.
To prevent this happening hold the clip back with needle nosed pliers as you push the battery in.

When the battery is fully down into the holder release the retaining clip.

Check the battery voltage.
Use the bare copper around the top right PCB mounting hole as a ground point.
A fresh battery should read around 3.3v

Replacing the PCB

Replacing the PCB is simply the reverse of the removal procedure.

Push the PCB in toward the back of the unit and ensure the Foot Controller Jacks and the Click Volume Knob locate through the rear panel holes properly.

Bring all the cable connectors from under the PCB back over to the top of the PCB.

This is the location pattern of the screws that hold the PCB in place:
The six coarse threaded screws go to the rear of the PCB.
The three fine threaded screws go to the front of the PCB.
Use the metal cable tie with the front left screw to neatly hold the two cable looms at the front left of the PCB.

Replace the PCB screws first, then replace all the cable connections.
The PCB screws are marked by the Black and White arrows.
The cable connectors are marked with YELLOW arrows
Fitting the cable to CN12 is the reverse of the removal procedure shown earlier

Reconnect the battery to the PCB circuitry by placing the Jumper over both pins of CP1 as shown in the left photo .
It’s a good idea to check the battery voltage at this stage incase there is an abnormal load present.
Use the Anode of D1 as the Positive point ( right photo ) and the metal bracket behind the PCB as the Negative point to take your voltage reading.

Replace the Rear Cover
Once you’re happy that all the internal parts are back in their proper place put the cover back on.
Remember to replace any SIMM or SYEMB06 expansion boards that were removed earlier.

The small screws go to the white circles, the large screws go to the Cyan circles.

Flip the SY85 over and power it up.

You will notice all the presets have been lost and the synthesizer settings are scrambled.
Load in the Factory Disk supplied with the SY85 to restore all the SY85 settings back to default.

You can manually check the voltage of the new battery by pressing this button sequence to bring you into the diagnostics menu:
[SHIFT] + [STORE] + [EXIT / NO] all held down in that sequence.

When you enter the diagnostics menu a message similar to this will appear:

After a few seconds the display will switch to the menu mode:

To check the battery voltage press the panel buttons in this sequence:
[+1] then [PAGE >] then [PAGE >] then [ENTER / YES]

The display will show the battery voltage reading similar to the photo below:

To exit out of the diagnostics menu press this sequence of buttons:
[EXIT / NO] then [+1]

The SY85 will now re-boot like it does at power-on

Your new SY85 battery should give you many years of service 🙂

// Document End


4 thoughts on “Yamaha SY85 Battery Replacement Guide

  1. Hello, I’ve not used my SY85 for a few years now and the battery has failed – it’s showing 0.1v so not much juice left! Are you able to let me know where I could purchase a suitable battery holder such as the one you have used, as this seems like the way to go rather than a new battery with solder legs? Alternatively, if I can’t find a match could I run short wires from the motherboard +/- connections and solder these to a battery holder and tape this in place?

    Either way, thanks for such a clear and informative ‘how-to’ guide on the battery replacement. I’m sure it will be invaluable once I get to that point.

    As an aside, I’ve just installed a Nalbantov USB floppy disk emulator and it works very well, so I’m very close to getting my SY85 back into fighting shape!

    Thanks again,
    Pete Turner

    1. Hi,

      It has been so long ago I cannot remember where I got the holder from. It was down to luck that I got one that had *almost* the same leg spacing as the holes in the PCB, I had planned to mount it near the original position and run a wire from one of the legs. A slight adjustment on the holder seen it mount straight on.

  2. Many thanks. I’ve ordered a couple, one from Farnell and one from Amazon. Both have a 20mm leg spacing. The one from Amazon looks just like the one you used, so hopefully I’ll get one of them to fit, perhaps with a little persuasion…


  3. Hello again, just to let you know that I carried out the mod to my SY85 today and all is well. A couple of hiccups along the way but everything is now working normally. Thanks again for publishing this guide, I’ve read it so many times I almost knew it off by heart before I started!

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