Signal Path Components

[patfont]

This is going to be a real neewbie question, but would like to learn a little bit here. What is the art, or how do you view a schematic and know which resistors are in the signal path on a circuit board. I am looking on the phono board and preamp board of my Marantz receiver. It is a 2220B and I am pretty much done restoring it but would like to do a little more. Thanks for any help or pointers here.

[Mooly]

It's not as quite as easy as that.

As your knowledge and experience increases you will begin to understand the operation of the circuit... what each part does and what the effect of changing any value might have.

You need a thorough grounding and background in electronics to do that.

No short cuts to doing that I'm afraid. But don't let that stop you asking questions because it's the only way you learn.

[patfont]

Maybe someone could help me out a little bit on showing me what resistors are in the signal path that are critical if any. Thanks in advance. See the 2 pics below. You can click on the pic and then go and view at any size including full.

[mickeymoose]

With the exception of R429, 415, 416 all resistors are part of the signal path, including feedbacks' R411 R423, R427 etc.
What you need to make sure of is that all resistors are metal-film, not carbon-film resistors. This design looks more than 20 years old and there is a good likelyhood that the resistors are carbon based. Metal-films will give you less noise and better temperature stability. E

[patfont]

Originally Posted by mickeymoose

With the exception of R429, 415, 416 all resistors are part of the signal path, including feedbacks' R411 R423, R427 etc.
What you need to make sure of is that all resistors are metal-film, not carbon-film resistors. This design looks more than 20 years old and there is a good likelyhood that the resistors are carbon based. Metal-films will give you less noise and better temperature stability. E

Yes it is probably 30+ years old. Thanks so much for taking the time to look at this for me. I would if possible like to do this in 2 phases, are there certain resistors in the path that would be considered critical that I could do first. There are 29 resistors on the board minus the 3 out of signal path leaves me 26 to do. If I could do critical ones first if that even applies I would like to go that route.

[DF96]

The concept of 'signal path' is one that is sometimes used, but almost always incorrectly. A good place to start is that all components are in the 'signal path'. If one does not affect the signal why is it there at all? Once you know enough to decide which ones are important you will know enough to ignore the concept of 'signal path'.

[Mooly]

For what they cost you may as well just do them all tbh if that's what you want...

I think you will find all the resistors are still perfect, but I can understand the satisfaction of you wanting to do this.

The most critical tend to be the higher value ones and as mm points out, so look at the feedback networks. And C421

Probably easier to say what isn't critical assuming they aren't obviously faulty (they won't be) and thats R421, 419 and R415. Neither is R429 feeding power to the circuit.

[patfont]

Hi and thank you I think I am catching on a little here. Can you tell me which resisters are in the feedback circuit? Thanks! All of the caps were replaced including the 2 tantalums.

[mickeymoose]

Think about what "feedback" means and what it does (or is supposed to do). E

[patfont]

My guess,

R411, R412
R423, R424
R427, R428 ???