Modified Silvertone Model 1421 Amp – Part One, The Tear Down

From the tail end of the vacuum tube era, a real Tone Gem in the genre of garage band tone.

Editor’s Note: This is Part One of a two part series on modifying the Silvertone 1421 guitar amp. This article is a work in progress, so please check back for additional info and updates.

The 1960’s Silvertone 1421 Combo Tube Amp (also originally sold as the Sears 10XL) is a great little vintage tube amp. It’s compact size makes it easy to carry to practice or a to small venue. It’s low 10-watt tube output (actually, closer to 5-watt) is perfect for the recording studio. It has two instrument inputs going into one channel, volume and tone controls, and a fantastic 12AX7 tube tremolo circuit, playing out to an 8-inch speaker. The sound here is definitely in the garage band category, but you can coax some great sounds out of this little guy.

The all-tube version of this amp was made from 1968 to 1972, and was later replaced with a all-transistor (solid-state) version in 1973. I picked this one up off eBay a few years ago. It’s a 1970 model and is all original, except for the brown speaker grille fabric (which is ugly!).

Below is a photo of my Silvertone 1421 after it first arrived. The vinyl covering, the controls, the faceplate were all in excellent condition for its age; no tears or scratches. The original vinyl handle was flexible and intact. The only problem this amp had was a stuck (frozen) power switch. I replaced the bad switch with a new heavy-duty toggle, and replaced the old two-prong power cord with a new grounded cord. When I powered it up for the first time it was amazingly quiet for an old tube amp.

1970 Sears 10XL Silvertone 1421

The knobs and faceplate were in great condition. The handle was still flexible and firmly secured to the cabinet. But the original toggle switch stuck (frozen).

1970 Sears 10XL Silvertone 142 Control Panel
1970 Sears 10XL Silvertone 142 Control Panel

Front view showing the replaced grille cloth over the original baffle board and speaker.

Sears 10XL Silvertone 1421
Sears 10XL Silvertone 1421 Front

Rear view of cabinet. You can see the new grounded power cord that I added.

Sears 10Xl Silvertone 1421 Back Cover
Sears 10Xl Silvertone 1421 Rear

The Sears product label on the rear panel showing the model number and vacuum tube layout.

Sears 10XL Silvertone 1421 Label
Sears 10XL Silvertone 1421 Label

A view of the chassis through the back panel vent.

Sears 10XL Silvertone 1421 View of Chassis
Sears 10XL Silvertone 1421 View of Chassis

Photo of the cabinet interior, showing the chassis and the original 8-inch speaker made by CTS.

Inside Sears 10XL Silvertone 1421
Inside the Cabinet

A closer view of the chassis.

Sears 10XL Silvertone 1421 Chassis and Speaker
Chassis and Speaker

The 8-inch speaker with ceramic magnet made by CTS (code 137).

Sears 10XL Silvertone 1421 Speaker
Sears 10XL Silvertone 1421 Speaker

Another view of the chassis, showing the power transformer, the filter capacitor can, the output transformer, and the tubes. The on-baord tube complement is one 6X4 Rectifier tube, two 12AX7 tubes for preamp and tremolo circuits, and 7189 power tube.

Chassis and Tubes
Chassis and Tubes

Here is the baffle board removed from the cabinet. The board was nothing more than 1/8″ thick Masonite.

Sears 10XL Silvertone 1421 Baffle
Sears 10XL Silvertone 1421 Baffle
Sears 10XL Silvertone 1421 Original Speaker
Sears 10XL Silvertone 1421 Original Speaker
Sears 10XL Silvertone 1421 Original Speaker and Baffle
Sears 10XL Silvertone 1421 Original Speaker and Baffle
Sears 10XL Silvertone 1421 Original Speaker and Baffle
Sears 10XL Silvertone 1421 Original Speaker and Baffle

Here is the cabinet with the baffle board removed.

Sears 10XL Silvertone 1421 Front Baffle Removed
Sears 10XL Silvertone 1421 Front Baffle Removed
Sears 10XL Silvertone 1421 Back Cover Removed
Sears 10XL Silvertone 1421 Back Cover Removed

The wiring is hand-wired and soldered.

Sears 10XL Silvertone 1421 Chassis
Sears 10XL Silvertone 1421 Chassis
Sears 10XL Silvertone 1421 Chassis Components
Sears 10XL Silvertone 1421 Chassis Components
Sears 10XL Silvertone 1421 Chassis Components
Old School Resistors and Capacitors
Sears 10XL Silvertone 1421 Chassis Components
Orange Drop Cap and Fuse Assembly
Sears 10XL Silvertone 1421 Chassis Components
Orange Drop Capacitor
Sears 10XL Silvertone 1421 Chassis Components
Old School “Chiclet” Capacitor
Sears 10XL Silvertone 1421 Chassis Components
Sears 10XL Silvertone 1421 Chassis Components

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