Why is there an extra resistor on these clones/layouts.

Started by pappasmurfsharem, July 26, 2012, 08:13:24 PM

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pappasmurfsharem

I'm looking at building an RM Octavia. I found a nice veroboard layout here.
http://www.aronnelson.com/gallery/main.php/v/TCobrettis-Stuff/album161/octavia_vero.gif.html?g2_imageViewsIndex=0
This layout seems to match up with nearly all schematics I have seen online.

Now here is a set of gut shots from an Octavia. Look at the "RM Octavia inside 1 through 5"
http://www.aronnelson.com/gallery/main.php/v/TCobrettis-Stuff/Roger-Mayer-Gutshots/

Every value and transistor seems to match perfectly in the vero layout, which also appears to match the TONEPAD.com RM Octavia

Except there is an extra 2.2M resistor. In both clones, that doesn't exist in the gutshots. In the gutshots I count 20 Resistors where on the clones I see 21

Anyone have any idea what is up?
"I want to build a delay, but I don't have the time."

R.G.

Probably pulldown resistor(s). All you need to do to have all this down cold is read the last decade or two of the forum.   :icon_wink:

You're starting up the curve. Keep asking, and go study the references you're given. You'll get there.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

pappasmurfsharem

I was thinking it was possibly a pull down, in just so used to seeing 1 Meg pull downs.
"I want to build a delay, but I don't have the time."

reverberation66

if you use the search function here there should be some information on pulldown resistors, what values are most suitable, and why.  I think 2.2M is fairly common for a pulldown resistor in a stompbox circuit.   

R.G.

When you are trying to suss out component functions, *always* think function first, then value.

R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.