SPARC Radio Museum - Sparton 270 Restoration

Restoring a Sparton Model 270
Gerry O'Hara VE7GUH
May 2008

Restored Sparton 270.

This Sparton Model 270 dates from the 1933-34 model year. The model shown here is the 'low-boy' cabinet version, but a Model 270 'Junior' was also produced - a table-top model with the same chassis, but deploying a smaller speaker unit. Both cabinets look a little 'dated' for this period and appear more late-1920's cabinet styles. As floor-standing sets go, this one is quite diminutive and could easily have been located in a room away from the lounge.

The chassis of the Model 270 is a simple Broadcast-band only superhet design and performs well given the simplicity of the circuit. The tube line-up is a 6F7 converter (triode/pentode), 6D6 IF amplifier (465kHz), #75 detector/AGC/first audio, #42 audio output and a #80 rectifier. Tone control is via a three-position switch.

This set was bought from a CVRS member who just could not get around to restoring it. The cabinet had a badly damaged top - the usual scars of a well-watered 'aspidistra' or similar plant placed on it for ornamental purposes (why did people do that!). The remainder of the cabinet was in fairly good condition, so when it was brought into the SPARC workshop it was decided to just re-finish the top and only lightly rub-down the remainder of the cabinet with super-fine steel wool ready to apply some fresh lacquer. Once the top was tinted to match the remainder of the cabinet, the entire cabinet was given several coats of walnut-tinted and then two coats of clear semi-gloss lacquer. The original speaker cloth was very faded and was therefore replaced with one of similar colour tones and design.

The power and output transformers both tested fine - good news. The chassis was then given a thorough cleaning and was entirely re-capped (though the original capacitors looked rather ugly, many of the paper capacitors were found to be serviceable on testing prior to disposal). A couple of resistors had drifted unacceptably high in value and were therefore replaced. Only one tube needed to be changed-out and the top cap (grid connection) repaired on another by a little careful cleaning, soldering and gluing.