Supro Thunderbolt Speaker Replacement

Today we'll replace a Supro Thunderbolt Amp S6420 original Jensen speaker with a Supro TB15.  It turns out to be a pretty good match to the vintage 1960's amp.

Let me start by saying:  If  you don't know how to properly and safely work on a tube amplifier, do yourself a favor and don't remove the amp chassis from the amp.  There are lethal voltages inside.  Don't touch anything inside the amp chassis. It's easy to replace the speaker by removing the speaker baffle, and then replacing the speaker.

As an amp tech, I wanted to make sure nothing suspicious was happening inside, so I removed the amp chassis. This also gives the viewer a better understanding of what's going on inside their vintage amp, without taking their own apart.
I begin by removing the tubes from the amp.

Then, I removed the chassis screws, and before pulling the amp chassis out of the cabinet, I removed the cabinet shielding wire screw.

After carefully removing the chassis, I can now remove the speaker from the cabinet.  This is how most speakers are removed- from inside the cabinet.  Since all the nuts were loose on the speaker lugs, I was able to remove them without a socket or wrench.

If your speaker needs a new 1/4" plug, now is the time to make a new speaker cable and install it.  Since this one had a plug soldered on, I made a new one and soldered it onto the replacement speaker.

Installing the speaker is the most difficult part and that was quite easy, actually.  You must be very careful, however to perfectly line up the screws with the speaker holes.  This takes a steady hand and some confidence.  Rushing this part will reward you with at least one hole in the edge of your new speaker. It has happened to me.

Once you have installed the speaker on the studs, you can now install your washers and nuts.  Tighten them with a wrench or socket to be sure the speaker is installed tightly.

Clean the contacts for the cabinet shield and reinstall it with the screw.
Reinstalling the amp chassis is a breeze, as long as you leave room for the amp to fit by rotating the speaker slightly to allow for clearance.  Since you did that, go ahead and reinstall the amp chassis into the cabinet.
Screw the chassis back into the cabinet with the screws you removed.

Reinstall your tubes.

PLUG YOUR SPEAKER BACK IN.

Power up your amp and give it a listen!