Hi all,


I have made a PCB layout of the EN tri-square VCO (EN-76 VCO option 2)
and I manage to put all the stuff on a 3" X 4" copper plate.
The one I had built is working so the layout is proof.

I didn't put the values of the passive component (for copyright reason)
but the EN VCO is about the same then the one in Barry Klein book "Electronic
Music Circuits" (fig 4-7  p.91) and also the one in "EN preferred circuit 
collection" from Bernie Hutchins. So you have to get one of this books.
Barry is really fast for sending the book, I receive it in the same week I 
order it (and I'm in Quebec,Canada). 


There are some modification on the original circuit : 

For those of you how had Klein's book, you must add the following buffer
(TL082):

-------------------------
|                       |
|  |-                   |
---|- --                |
   |     ---            |            R15
   | IC5     -----------|-----------\/\/\/\/\/--------->to inverting input IC6
   |     ---            |                         |
---|+ --                |                         |
   |-                   |                         |
                        |                         R21
       ------------------                         |
       |                                       ------
       |                                         --
       |   |-                   
       ----|+ --                
           |     ---                        R29 now R105
           | TL082   ----------------------\/\/\/\/\/--------- TRI Out
           |     ---     |                               
<----------|- --         |                              
 to     |  |-            |                                
 R22    |                |
        |                |
        -----------------|
        |
        |
        to R33



Another modification is the sync input that Gene Stopp made:



                  Csync        Rsync

   sync in --------||---------/\/\/\/------------>to inverting input of IC6

                  .015 uF          39K              (3080) for both book.



There is a Coarse tune trimpot on the pcb and more CV input (just more 100k)

          TPinit=100k
     +15 /\/\/\/\/\/ -15
              ^
              |
              --------\/\/\/\/\/\/--------
                       RIN4=300K


You could replace one of the input resistor (ex: R1) by a 2.2Meg that go
to a fine tune panel pot. You could also route one of the 100k input resistor
to a coarse tune panel control. 


I had use the component naming of Klein's book.

This is the conversion name you must follow if you use the Electronotes
book instead of Klein's one.


Klein  EN          Klein  EN           Klein  EN
--------------------------------------------------
R1    R80           R23  R102           R45  R116
R2    R81           R24  R99            R46  R117
R3    R82           TP25 TP9            R47  R120
R4    R83           R26  R101           R48  R121
R5    R84           R27  R103           R49  R122
R6    R85           R28  R104
TR7   TR8           R105 R105           C1   C10
R8    R89           R30  R106           C2   C11
R9    R86                               C3   C12
R10   R87           R32  R107
                    R33  R109
R12   R88           
R13   R94           R35  R108
R14   R95           R36  R115
R15   R96           R37  R110
R16   R97           R38  R111
R17   R91           R39  R112
R18   R90           R40  R113
R19   R93           R41  R118
R20   R92           R42  R119
R21   R98           R43  R114
R22   R100          TP44 TP10

Change for both:

Use MAT-03 instead of AD821

The MPF-102, 748, 3140 and 3080 remain unchanged
(Be sure to check the pinout I write on the layout for the MPF-102, the shape
of the component is reverse)

All others chips are now TL082

The chips type are written on the layout.

I strongly recommand that you try two PNP instead of the MAT-03 to see if
everythings is OK (you would not want to blow a MAT! $$$ but don't plug
the pnp the wrong side like I do, the 3080 would die!)

You could just start with the square oscillator : just don't plug the jumper
wire that go from the 3140 to the TL082 buffer (triangle out). 

The PCB is in postscript and I put it on two pages: The first is the layout
and the second is the upside view of the component AND jumper wires. 
IMPORTANT : You will see the layout like if you could see thru the epoxy
plate. The idea is that you could put the 2 pages on top of each others and,
when see thru light, you will see exactly where the component goes. Another
reason is that you could photocopy it on a transparent sheet and iron it on
the copper plate (the ink should be on the good side of the sheet for the 
transfer). That technique didn't work with all type off ink, sheet or copper
(it work best for me with cheap copper plate). Anyway, after the transfer is
done what I usually do is redo the traces with a permanent ink marker (you
just have to follow the existing traces) or better with a Liquid paper pencil!
My experience with permanent ink is that it seem to dissolve a little bit when
put in the etching solution.

I wish to thanks Gene Stopp for his help, Tony Patrick Blake for the EN Vco
schematic and Barry Klein for his book and all the other people in the Synth-DIY
Mailing list for making me learn more about electronics.

If you are succeful with this layout, drop me a line!


Happy modules building!


Yves Lefebvre     REMOVE_THISivanohe@AND_THISabacom.com