IMPORTANT: the two 1N2001 Diodes are not (!) zener diodes, but normal silicon diodes, with voltage drop from 0,7 up to 0,8 Volt (DUS=Diode universal Silicon, 1N4002 or 1N4003 or 1N4004). All about the signal tracer, its importance, and how to make it. Every (serious) electronic hobbyist needs one. In fact it is a small high quality audio amplifier with a high impedance input, seperated for DC by non polar input capacitors (range: 470 N = 0,47 uF up to 1 uF or 3 uF non polar!). It is a very (!) useful device because you can trace the signal through a radio or amplifier circuit or whatever circuit and find faults and defects.. E.g. when the signal disappears or gets distorted you can hear it via the loudspeaker. Also good to trace (e.g.) a TV signal on a plug etc. (typical digital sounds).
Much more info about good audio amplifiers and loudspeaker boxes in my book: "Schematics 2, audio amplifiers and loudspeaker boxes", author Ko Tilman. Available via bookshops or Amazon, but the cheapest price = via the Lulu website.
My channel trailer
[ Ссылка ] gives links to the video's on my channel in thematical order (audio, radio, generators, switches, etc.)
By the way: all resistors in this schematic are 0,5 Watt.
Important: the pin connections from the BD 140 (PNP) BD 138 (PNP) and the BD 137 (NPN) / BD 139 (NPN) are all the same (see video).
Reading from the side with the printed type number (= the front): from left to right it is E - C - B. (emitter - collector - base)
All the videos hat I have published on You Tube can be found via my Channel Trailer: Link is
[ Ссылка ]
In thematic order you can find these video’s under the “comments” section.
Important: to find all the links to the (+/-700) video’s on my YT Channel, select, in the comments section, “NEWEST FIRST”
My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there.
[ Ссылка ]=
There is an important video via which you can buy a document where I give links to many of my video’s, published between 2010 and 2018.
Link is: [ Ссылка ]
Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics) and important adaptations to the circuits.
Be aware of that, I saw on the internet my circuits reproduced in a poor or even not proper way. I can not help that, sorry.
