New (old) amp - schematic missing - councils for a reverse engineering job ??

[kagliostro]

I got an old Auso - Siemens stereo amp ( ELA 811 or ELA 8110 don't read well)

it is a stereo amp

2 x ef86

2 x ecc81

4 x ecl86

the construction is near a nice point to point

I'm not able to find the schematic

so I would like to do a "reverse engineering" job, my first one  

have you a planning for that ?

How do you proceed when looking to the circuit to extract the schematic ?

MANY THANKS

Kagliostro

[HotBluePlates]

Pick a starting point, maybe the output tubes and output transformer. Draw them, with all connections and parts. Work outward from there.

You might need to use a meter to check continuity, to see where connections are made that you can't see easily.

Plan on a very messy first drawing, and having to re-draw a couple times to make it neat and readable.

[RicharD]

I agree with everything HBP said.  I usually try to draw in clusters, ie.  power supply, output stage, pi, input stage(s).  Sometimes it's helpful to mark stuff as you go using colorful tapes or clips etc.  Once I have a drawing done, I triple check it using a highlighter marker.

[kagliostro]

MANY THANKS to both friends

That is a good start point

Kagliostro

[Shrapnel]

Pick a starting point, maybe the output tubes and output transformer. Draw them, with all connections and parts. Work outward from there.

You might need to use a meter to check continuity, to see where connections are made that you can't see easily.

Plan on a very messy first drawing, and having to re-draw a couple times to make it neat and readable.

+1

My usual starting point is at the inputs. (My theory is it's the beginning link of the chain, so a good place to start. At the outputs is just reverse of my thoughts, but probably just about as easy. IMHO, starting in the middle can be very confusing.)

So choose your starting point, and start drawing.

[jjasilli]

My 2¢: I work backwards, like Hotblue suggests:  1st power amp -- OT secondary > OT primary > power tubes > PI (if any); then power supply starting at the power chord.  For me, this simplifies the process and gets a lot of any rat's nest wiring mentally organized.

I skip pencil drawing and go right to the Express Schematic program.  With a little practice and a small library you can paste in components or circuits; and define & move whole blocks of circuits around if you find you need to insert something previously overlooked.

[DummyLoad]

i usually start with the power supply, then work my way back through the output stage, on to next stages, drawing the input stage(s) last. my experience is that the drawing flows on paper neater and easier that way.

[Tiny_Daddy]

I open Express.sch, plop down the necessary tubes and proceed to fill in the blanks.

[kagliostro]

Many interesting cues

if I could have the amplifier near the PC I think it will be interesting by drawing in a program instead on paper, but as it is my first job I'm not sure if it is (at the moment) convenient to me

I'll try to think a little to your councils and than start with my "compromise"

MANY THANKS to all

Kagliostro