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Old 16th Feb 2011, 1:12 am   #21
Herald1360
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Default Re: Circuit Diagrams for Beginners

Quote:
Originally Posted by Boom View Post
I recall reading somewhere that the nicest thing about valve circuit diagrams is that voltages get higher the further up the sheet you go.
I think that is just a UK convention. Across the pond the convention seems to be for all the supplies to be at the bottom. It doesn't half make some circuits difficult to follow. As for circuits with the valves horizontal..... well it makes sense for grounded grid circuits but otherwise it's 'orrible.
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Old 18th Feb 2011, 5:56 pm   #22
terrykc
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Default Re: Circuit Diagrams for Beginners

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Originally Posted by Martyn Stevens View Post
The diagram seems to leave out large amounts of stuff.
I picked on this quote because it is probably the most confusing. Paradoxically, it is done deliberately to (usually) make diagrams clearer!

From your post it is obvious that you will be dealing with amplifiers using parallel heaters. To show the heater connections would require one or, with good quality equipment, two lines across the diagram connecting the heater connections on every valve to the appropriate winding on the mains transformer.

There are two points here:

1. These lines would exist on every diagram in exactly the same way;
2. These lines also get in the way of the rest of the diagram, cluttering it up and making it harder to read.

Solution: as they're always there and (it is assumed) everybody knows they're there, there's no need to show them!

But, if you don't know that ...

If you find the mains transformer, there will be a winding marked 0 - 6.3V or 3.15 - 0 - 3.15V (or similar) and possibly nothing more than an arrow on each connection which you are assumed to know means that they are connected to the heater pins on all the valves or, sometimes, all of the valves except one. In the latter case, there will be another heater winding which, in all probability, will be shown complete with connections to the valve it serves.

There are other 'short cuts', though some have the reverse effect of making diagrams harder to understand ...

When I first started learning about what we today call 'electronics', circuits always showed the earth line (chassis) at the bottom - often nice and bold for clarity - and the HT line along the top. However, it is possible to draw a circuit without either!

Every earth/ground connection just has an appropriate symbol on it and the HT connections will have arrows which might (if you are lucky!) be labelled HT or HT1, HT2, etc., if there is more than one HT supply but could just as easliy be marked A, B, C, etc., which isn't as useful.

There are many ways of drawing circuits: some are very clear and easy to follow whilst others defy most efforts of even the most highly experienced to yield their vital information - with many variations in between.

There are other pitfalls for the unwary: a resistor, for example, may be drawn as a zigzag line or as a very slim rectangle. The first time that I encountered the latter, it was obvious what they were because they were drawn in all the places I expected to see a zigzag line!

It still took a little time to get used to them. Now, I couldn't tell you if the circuit I looked at an hour ago was drawn one way or the other ...

Your prime interest is obviously with audio equipment only, to start off with, at least, so there is no point in confusing the issue by studying radio circuitry (by which I mean the part of the circuitry which handles only RF) and concentrate on the audio sections. Books, etc., dedicated to audio amplifiers are ideal but that doesn't mean that the relevant parts of books covering a wider spectrum should be ignored!

If the Mullard book you referred to is the Mullard Book of Audio Amplifiers, it should be very helpful.

Can you scan the circuit you referred to in your original post?

If you post it so that we can see it and ask a couple of questions for starters, the answers will be tailored to your circuit. Otherwise, because there are so many variations, as others have pointed out, answers to your queries may appear as incomprehensible as the circuit!
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Old 23rd Feb 2011, 11:25 am   #23
qualityten
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Default Re: Circuit Diagrams for Beginners

A thread of this kind is really helpful, as it covers just the kind of things which are assumed elsewhere. Post #18 alone is worth printing out until that information is well lodged in the memory.
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