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.
This circuit is from a1970 documentation. R1 may have 10k and P1 47k. The transistors can be BC558...
In the figure we have an amplifier using the 741 operational amplifier without the need for a...
This filter was found in old Raytheon documentation. The circuit makes use of operationals of the time, but...