Economy 6 Watt Push-Pull Amplifier Kit A-4

• alternative name: Heath Company

The Heathkit A-4 is a vintage monaural (mono) audio amplifier introduced by the Heath Company in 1947 as part of its first line of electronic kits. It was a simple, low-power unit developed from circuits found in the Radiotron Designer's Handbook and is considered rare today.

Technical Specifications:
The A-4 was a primitive tube-based design built on a single sheet-metal chassis. According to historical Heathkit records: 
Power Output: Rated at 6 watts.
Circuit Design: Based on standard designs of the era, it utilized surplus wartime electronic parts.
Output Tubes: Typically employed a pair of surplus metal-type 6L6 or 6V6 output tubes.
Transformer: Featured a potted output transformer, likely manufactured by Chicago Transformer. 

Maintenance for Collectors:
If you are restoring an original Heathkit A-4, experts from Vintage Radio Info and Nostalgic Kits Central recommend the following:
Component Replacement: It is critical to replace original paper or "Black Beauty" capacitors, which are known to short over time and can damage rare output tubes or transformers.
Powering Up: Always use a variac to slowly bring up the voltage on vintage tube equipment that has been in storage to avoid blowing internal components. 

Here you find 816 models, 799 with images and 515 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Heathkit (Brand), Heath Co.; Benton Harbor (MI)