ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi I am just starting the planning phase to restoring my 3400 and going through a component matching process Capacitors & Transistors etc but what are these circled, I can’t find a symbol reference?
Also for the diodes symbol are these something special perhaps Shockley Diodes? Or is it just symbology from he 70s and in fact there are just a semiconductor diode, the most commonly used type today with a p–n junction?
Any help appreciated, sorry if the photos are a bit poor. Ok why are my photos not loading suggestions?
Ahh sorted and found out how to load photos, bit clunky but it worked!
How are you saving the picture? JPG is usually fine, save in a convenient file and then go to options and use browse to find it.
Peter
You have circled the darlington transistors in the output stage, two diodes in the safety circuit and three band-pass filters in the tuner.
"component matching process" What is that and what is the purpose?
Martin
Hello Martin
When I say component matching it really means do I understand the schematics I have?
The symbols for what you have identified circled as three band pass filters I’ve not seen before and not sure how they work although I do understand R, C, L filters.
Ive not seen a symbol for the Darlington Transistors before and don’t know their make up, PNP or NPN or other? but did recognise them as some form of transistor.
The diodes in the safety circuit, the symbol themselves, on the schematic I’ve also not seen before although I do recognise this part of the circuit as a protection circuit, that’s why I started to ask what type of diode are these?
I’ve much to learn before I even consider opening this unit up, my process is build my knowledge of this 3400, the circuits and components used so I understand what I should expect to see at various test points and or individual component test as well as reading all posts on failures modes and likely component failure.
Any further info on the questions above would help me further, many thanks Steve
Hello Peter I uploaded the jpegs to my images areas then tried to load from three via insert media but it just says loading. Perhaps an iPad compatibility issue, I’ll try again via Mac
A band pass filter will only let a certain frequency or frequency range pass. Everything else is grounded.https://en.wikipedia.org/wiki/Band-pass_filter
They are ordinary diodes (Schottky diodes are different components and have a different symbol).You can see, that all other diodes are drawn using the same symbol.