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Check and Change a Power Fuse

  • Updated

Warning

Amplifiers utilize levels of voltage that may cause serious injury or bodily harm. If you are unfamiliar with the maintenance of tube amplifiers, we recommend seeking assistance from a trained amplifier technician.

Before accessing and checking the power fuse on your amplifier, first ensure that the amplifier is turned off and unplugged.

Checking the Mains Fuse

Fuse housing beneath power inlet
Plastic fuse housing below power inlet

The mains fuse on your PRS amplifier is located inside the plastic power outlet housing. The bottom compartment is accessible using a small flathead screwdriver. In brand-new PRS amplifiers, there will be a spare mains fuse stored in the compartment.

To verify whether the fuse has blown or is still in good condition, perform a continuity test with a multimeter:

  1. Ensure the amp is turned off and unplugged.
  2. Carefully remove the fuse from the compartment.
  3. Set your multimeter to read resistance (ohms).
  4. Touch the probes to the metal contacts on both sides of the fuse:
    1. A small resistance reading indicates that the fuse is still good.
    2. No reading or an “OL” (open loop) reading indicates that the fuse has blown.
  5. If there is no continuity or an open loop, replace the fuse with the spare.

 

Changing the Mains Fuse

If the fuse needs replacing and the spare isn’t available, replace the mains fuse with one that has the exact values described on the back of the amplifier. The replacement fuse must match the current rating, voltage rating, and whether it is a time-delay (slow blow) fuse.

Fuses can be sourced from electronic component suppliers such as Mouser Electronics or your local hardware store.

Blown Fuses

If the fuse has blown, check the following to prevent further issues:

  • Ensure your amplifier and speakers are properly loaded.
    • Improper loading of the amp head and speaker cabinets can cause components to overheat, which can result in a blown fuse.
  • Ensure your amplifier is properly connected to all speakers.
    • Loose speaker wires may result in an electrical short and blown fuse.
  • Ensure your amplifier is in a location with adequate ventilation.
    • Leave space between the back of the amplifier and wall to ensure airflow to the tubes and reduce the risk of fire.

If the amplifier blows a fuse immediately after replacement, and all the above actions have been taken, there may be an issue with an internal component. At this stage, the amplifier would need to be seen by an amplifier technician.

For assistance in sending your PRS amplifier in for factory service, please feel free to reach out to our customer service team.

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