This can be considered a complete laboratory for the repair professional. A full featured signal tracer with 13 tubes. The circuit is from the March 1946 issue of Radio Craft.
We have already explored this configuration in several projects on our website. What the circuit does...
P1 on this Radio Shack circuit is a 6 V lamp with current up to 500 mA depending on Q2. The...
The transistors of this timing circuit may be more modern types such as BC548 and BC558. The...