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**David Schwab** · 04-18-2007, 01:27 PM

Originally posted by The Captain View Post

Hi, Im using new bits: opamps/ ICs etc. My Q is how to tell their "polarity" to mount. My build http://www.generalguitargadgets.com/...ms/catrmpl.gif. IC areas, or indeed my components have no obvious signs of left, right upside or down, & now I'm not even sure these pcb types are 'reversed' at all!..

I had assumed these track/ pcb layouts were 'backwards' (as writing was reversed) so when flipped components mount on top, track underneath.. but I've just seen similar reversed writing print tracks' adjacent layouts having ICs 'right' way round, or pin 1/ 'o' ident top left or NOT reversed- ie (pdf): http://www.tonepad.com/getFile.asp?id=101. Totally confusing me..

1) Are these pcbs reversed or not, if so why does (pdf) link's ICs have pin 1/ 'o' ident top left? or are they NOT reversed, if not why writing backwards??

2) IS the 'o' actually an IC's ident? on a few I have this 'o' is on lhs corner; others have a semicircle mark on one end; others such as a 5532 and a LM741 have no ident at all- how do I know which way to use these?

3) Just to rub my nose in it, I've a CLM6000 subsitute (a Silonex Nsl- 32) with no discernable markings (bar 2 shorter legs) & the tremolo layout's CLM6000 (top lhs) having 2 alien symbols I cannot even locate anywhere on www!!

All utterly baffling.. can anyone help? thanks Capt

This really isn't baffling at all..it's very standard stuff.

You are looking at the component side of the board, not the trace side, which is why the writing is backwards. This is showing how to load the parts on the PCB.

The "o" at the end of the IC is indeed the indent. IC's either have an indent on the end where the #1 pin is, or a dot or hole by the #1 pin. The 1 pin is always on the upper left looking from the top (with the indent up). See the attached picture for the 4049U IC pin layout for an example.

The 2 "alien" symbols on the layout for the CLM6000 are a diode symbol
(-|<-), which is the light emitting part, indicating the polarity of the internal LED, and a standard resistor symbol:
( /\/\/\ ) which is the photocell part of the optocoupler.

Here's the "alien symbols" as they relate to the NSL-32:

These are standard schematic notation symbols. The problem is many of these online schematic sites don't use them, and instead draw graphic representations of what the parts look like, and not the schematic symbols, which is bad practice. It's like learning TAB and not how to read sheet music.

You need to see the data sheet for your replacement part, it will indicate which lead is which.

From looking at the data sheet I found by Googling "Silonex NSL-32" (http://www.silonex.com/datasheets/specs/103708.htm)

The two short legs are for the LED. There should also be a color dot by the cathode (-) lead of the LED. This must be installed with the correct polarity to work. The photocell end is not polarized, and can be installed either way.

You should pick up a copy of Craig Anderton's book, Electronic Projects for Musicians, he explains how to read schematics. This circuit is one of his also.

Attached Files

**Mark Hammer** · 04-18-2007, 01:45 PM

There was a couple of us (myself included) back in the early days of sites like GGG and Tonepad who had simply not shifted our mindset from the old days of photo-etch and Sharpie pens to the press-and-peel approach, and inevitably etched some boards "backwards". I have a Small Stone that I had to bend the pins backwards on all the precious CA3094 chips just to get it working, and had spent a couple of months trying to debug a Dr. Quack before I realized what I was doing wrong.

The result of those accumulated errors was that layout providers essentially agreed to put text in the PCB pattern which would help to identify the orientation of the mask pattern as being "old world" (photo-etch/Sharpie) or "new world" (toner transfer). The turquoise traces and writing you see in the GGG layout are an "X-ray" view; essentially what you would see from the component side if the circuit board were clear.

**The Captain** · 04-18-2007, 11:52 PM

Superb help- many thanks indeed David. The alien symbols on layout I didn't recognise as an led at all (?), slightly differring as it is confused me.. now that makes sense- as does the nsl diagram which was complete gobbledegook and unrecognisable as being of any use at all before. That books a good idea too. I still have an IC (or an eight legged whatsit) with no 'o' tag or any ident at all- Ill dig it out and specify which- so I'll need IC sockets to flip and see, which, is tricky when I copy track layouts assuming they need reversing so I have the bloody ICs upside-down underneath a now raised board!! a muppet I am; a 1st rate diy tinker I am not! cheers Captain

**The Captain** · 04-19-2007, 09:32 AM

Can anyone have an educated guess at which side l or r the clm6000's led (top half) cathode - is here? http://www.generalguitargadgets.com/...s/catrmpl.gifI I presume the outside rail, but bttm rhs cap's + leg joins it (is this a typo do you think?).

Secondly another educated guess if you would: the two IC's, have 'ovals' at bttm on layout- do you think these are most probably the 'o' / 'top' ident?

Thanks- a simple seemingly but thoughrally confusing diagram! Captain.

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