Fuse Replacement Guide
Did your Three Sisters or Mangrove suddenly become unresponsive?
Not to worry! If the module was originally purchased before June 2017, the issue is almost certainly with the module's fuses and is a straightforward fix. On some PSUs, including the Doepfer PSU-3, the Pittsburgh Structure PSU, and Trogotronic PSUs, the original fuses on early production runs of Three Sisters and Mangrove can become permanently tripped, however no damage to the rest of the module occurs. This requires replacing the fuses with the upgraded ones that are on all post-June 2017 modules.
Confirming Fuse Version
You need to identify if your module is an old module which was built with the original fuses, or if it has the new fuses and is suffering from a different issue.
- Turn off your synthesizer.
- Remove the module from its case, disconnecting it form the power supply.
- Gently detach the rear PCB (the one with all the circuitry on it) from the interface PCB (the one attached to the panel and potentiometers). Take care not to bend any of the pins on the interface PCB. Set the interface PCB down somewhere safe.
- Inspect the upper right area above the female header on the rear PCB, looking for the two fuses, marked F1 and F2 on Three Sisters and P1 and P2 on Mangrove. If they are green and have small text printed on the green area, then proceed to the next section of this email. If they are light blue with no text, then the module already has the upgraded fuses and does not need them replaced! See below for a reference image. If the module has blue fuses but is not powering, please send us an email.
Replacing the Fuses
If you have DIY skills, it's an straightforward fix. If not, you can provide these instructions to your favorite local synth tech (or anyone handy with a soldering iron), or if you do not have one, contact us via email & we'll arrange a repair.
You will need the following:
- 2x Murata PTC Resettable Fuse PRG21BC2R2MM1RA
- Soldering Iron + Solder Braid + Solder
- Rubbing Alcohol + Q-Tips
Please read all steps before carrying out the fuse replacement so that you are familiar with the order of operations. Watch this reference video for a quick runthrough (password: threefix).
- Locate F1/P1 on the PCB.
- Place the tip of the iron flat across the top of the fuse so that it is touching the solder joints at both terminals of the fuse. Then add solder on top of your iron in order to conduct heat to both of the terminals.
- Once the solder at each terminal has melted, use your iron to gently swipe the fuse to the side and then up and away off of the pads. Be careful not to disturb other components in the area.
- Wipe your iron off on your cleaner sponge or golden fleece to remove the excess solder and the fuse from the tip of your iron.
- Use solder braid to remove any remaining solder from the fuse pads.
- Place new solder on one of the two pads.
- Pick up one of the new, upgraded fuses with your tweezers in your non-iron hand.
- Touch your iron to the pad with solder on it, and once it melts, use the tweezers to slide the new fuse into place.
- Once the new fuse is properly aligned, remove the iron from the pad while still holding the fuse in place.
- Solder the other end of the fuse to the pad.
- Use a Q-tip dipped in rubbing alcohol to clean the pads.
- If you have a multimeter, you can use it to confirm that you successfully installed the fuse by checking for continuity from one terminal of the fuse to the other. There should be continuity (or a couple ohms resistance).
- Locate F2/P2 and repeat steps 2-12.
- Carefully re-connect the rear PCB to the main PCB, ensuring that you do not bend any pins and that all pins are perfectly aligned - make sure you do not commit an "off-by-one" error!
Congrats, your module should be as good as new! If you have any questions or problems, shoot us an email at firstname.lastname@example.org.