signal injectors

[Yorkie]

Well done to them.

Sorry to hear they had a bad experience on another forum - no 'roost rulers' or 'tall poppies' here - no dramas.

A handy companion to the signal injector is a signal tracer - basically just a small amp. Lots of circuits about on the net, some using transistors, others using an IC such as an LM386.

I've mentioned before that Vellman do an excellent tracer/injector kit ('K7000') on a compact plated through hole PCB with a volume control for the tracer amp, and a level control for the injector. You get a nice clean sine wave from the injector - nominally 1KHz, but  as often as not it's a bit higher than that. Not important, it has harmonics going way up in frequency anyway. I've built several over the years, often as gifts to friends. I've attached some pics of one that I recently built, and a scope pic and frequency counter readout of one that I built a little while ago (1.25KHz). 

Doesn't need to be in a fancy box  - a plastic project box is fine.  They soon earn their keep.

The kit is widely available from several sources for about a tenner. (Speaker, sockets, knobs, switch etc not included).

https://www.esr.co.uk/products/frame_test-equipment.htm

 The construction manual is here:

https://www.esr.co.uk/manuals/k7000.pdf
 
Hope that's of interest.