FT-817 internal battery not working? Here's a potential fix

If your FT-817 has stopped powering up from the internal battery but works from external power, then maybe the internal battery fuse has blown.

There is a small PCB mounted fuse to protect the battery and radio. This fuse can blow, if it does your radio will not work from battery power.

This page will describe how to test the fuse and describe how to make a repair.

Symptoms of a blown internal battery fuse FT-817

The symptoms for a blown internal fuse are as follows (there are other possible causes so do check these first):

  • Unit appears to charge the internal battery, but the battery will not power the radio
  • The radio works off an external power source

Note: Make sure the battery is fitted and connected

Note: Make sure the battery is not discharged

The internal battery fuse

The internal battery power circuit has a resettable fuse in series with the battery. Unfortunately, resettable fuses don't always reset.

If your battery is shorted out, or the battery is connected with reverse polarity when trying to connect the plug, this fuse will go pop. 

This could be the problem, a blown fuse

Yaesu FT817 charging fuse
FT817 charging fuse
Yaesu FT817 internal battery fuse repair
FT817 internal battery fuse repair

Parts and tools required

First, you'll need to order the following components:

  • SMD Vishay MFU0805FF03150P100  3.15 amp fuse

These fuses are available from most online auction sites. A pack of ten should cost around $1.



  • Solder wick and solder sucker
  • Screwdriver
  • Fine soldering iron
  • Fine solder
  • Multi-meter with diode test function
  • ESD protective mat and strap etc.
Similar to the 0.35amp device
Similar to the 0.35amp device

Make the repair

Please don't try to replace this fuse if you are not confident with the removal and refitting of SMT components. Some care is needed when replacing these devices. Consider asking somebody who is skilled with these things if needed.

  1. First, remove the battery and battery lid.
  2. Remove the top cover of the FT-817 by removing the screws from the top, sides and rear.
  3. Next, identify the resettable fuse.
  4. Using your multi-meter, test the fuse and check the continuity.
  5. If the fuse is open circuit, de-solder and remove. This can be done by move your soldering iron across the fuse many times, eventually it should come loose.
  6. Clean the pads with solder wick.
  7. Place the new device in place (be careful), hold the device using your fingernail, and heat one side. This should be enough to hold it in place.
  8. Solder the other side, then solder the first side properly.
  9. Check your work (use a camera or magnifying glass).
  10. Reassemble the unit, connect the battery and switch on. The FT-817 should power on under battery power.

That's it! Your FT-817 should be fixed.


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