FIF : Replacing A Broken Fuse Holder

Written by
Logan Tabor
Published on
January 21, 2021 12:29:22 PM PST January 21, 2021 12:29:22 PM PSTst, January 21, 2021 12:29:22 PM PST
Welcome back to Fix It Friday.  Today we have a broken part to fix, and while the procedure isn’t all that complicated, it’s still a crucial piece of the amplifier puzzle.  This problem can arise for literally anyone; the occasional gigger, the full-time touring artist, studio pro, or bedroom guitar god.
The fact is, anytime we move our gear around we risk causing damage to it, especially if we are getting help from others who may not cherish our little electronic babies the way we do.  In my case, I was moving an amplifier out of storage and I guess at some point it must have taken a hit!  When I turned it on and got it warm I noticed a burning smell; I checked my fuse holder and found it was bent.  When I took the fuse out, I saw it had been shattered and was being barely held together by the actual fuse holder apparatus.  This type of little bend can happen fairly easily on any part of the front or back panel of an amp, it just takes that one unfortunate bump.  So, let’s replace this little bugger and get back to rocking!
Today we will need the following tools:
Fuse Holder (This will vary depending on your amp)Fuse (This will vary depending on your amp)Soldering IronSolderPhillips Head ScrewdriverPliersCell Phone (Specifically the camera)Multimeter

As always, the first thing we need to do here is remove our back panel and chassis so we can get to the amplifier’s guts; so break out that screw driver (or drill), get the back panel off, unplug your speaker wire and any reverb tank connections, and then get that chassis out of the cabinet and onto your workbench.  Let’s direct our attention to the fuse holder and surrounding area. Take some time to study the connections on the fuse holder’s lugs; see what’s coming in, where it’s coming from, etc. Then, it might be best to bust out your cell phone and just take a picture of how the fuse holder is wired in; this way we can have a visual reference when we go to install the new fuse holder.  
Note: With my particular fuse holder there are only two wires connected and it does not actually make a difference which lug they are connected to.  However, taking a reference photo is good form for future projects and can really save you, so it’s best to go ahead and make this a habit!
I’m working on the fuse holder in a Blackface Deluxe Reverb Style Amp, so my connections look like Image 1A below…




You can see one of my lugs is connected to one of the black primary AC leads of the power transformer, and the other is connected to the black (hot) wire of the power cable.  If you are working on a Blackface Style amp you should have an extremely similar -- if not identical -- situation on your hands, but if you are working on any other type of amp, things could be different so study your connections carefully (and use that reference picture).
Note: This is a fairly safe procedure provided we do not have our amps connected to power.  Make sure your amp is unplugged and turned off, and do not touch any internal components apart from those referenced below.
Moving on, we need to free up our fuse holder by removing those soldered-in connections, so let’s heat up our joints and pull the wires loose...


Once the fuse holder has been freed from its connections, we can loosen its fastening nut using our pliers or preferred tool (Image 2A).  You should be able to just give it a little twist with the pliers and then finish it off by hand once the nut is loose enough. Then remove the fuse holder and set is aside; you should now have an empty chassis cutout (Image 2B).  




It’s time to put the new fuse holder in so just insert it the same way the old fuse holder was inserted, fasten down the nut by hand as tight as you can, and then finish it off with the pliers -- the exact reverse operation of what we did to remove the old fuse holder.  
Once you have the fuse holder fastened in, you’ll notice the lug on top of the fuse holder is pushed down flat against the plastic housing.  We need to manually bend this lug upwards so we can get our lead through and solder it in. This can be done by hand; just get a fingernail under the lug and bend back gently until you have enough clearance to get wire through (Image 3A).  



Now it’s time to get those leads soldered into our new fuse holder.  Using the picture you took at the beginning as reference (for posterity’s sake), insert the appropriate lead into the appropriate lug, heat the lug briefly and apply the solder…




Okay our leads are in, now we can put the fuse into the fuse holder and test for voltage.  Once the fuse is in, plug the amp into the wall and turn the power on. Put the ground probe of your multimeter directly onto the chassis, and put the hot probe on one of the lugs you just finished soldering (Image 4A).  You should be reading around 120VAC (if you are in the US), or whatever the typical wall voltage is in your country. I’m reading right around 123VAC so I’m good to keep moving forward.




Now that we’ve fixed our bent and broken fuse holder, we are ready to rock on this glorious Friday!  Reinstall the chassis, plug in your speaker and reverb connections, screw down your back panel, plug her in, and let her rip!  We hope you’ve found this tutorial useful. Thanks again for tuning in and we look forward to seeing you next time.