
[This was originally a 40-col PETSCII file.]


2nd_dox

September 1, 1988 - 10:00pm

Second SID Chip Installation
----------------------------
Copyright 1988 Mark A. Dickenson

This information and software is COPYRIGHTED and made available on a 
SHAREWARE basis.  This file can be freely copied and distributed as long 
as it is not SOLD.  This information cannot be used to construct and sell a 
hardware device without receiving prior permission from the author.  
There is not a set fee for the use of this information.  Just send in 
whatever you feel the information is worth.

If you have any gripes, complaints, suggestions, COMPLIMENTS or DONATIONS 
of any sort please send them to:

 Mark Dickenson
 600 South West Street
 Nevada, Missouri  64772

Adding an extra SID 6581/6582 chip

This is not a project to be tackled by the sqeamish or people who are deathly 
afraid of opening their computer just to take a peek inside.

Now let's get rid of the nasty stuff first.  No liability is assumed with 
respect to the use of the following information.  In other words if you 
screw-up trying to install this modification, then it's your responsability.

  YOU DO THIS AT YOUR OWN RISK!!!!

If you do not feel up to it PLEASE take it to a Commodore repair center 
or a repair service that can work on computers and let them do the 
installation.  I will warn you that most Commodore Repair Centers will not 
or do not like to do this modification.  When they do, it can be expensive.
If you belong to a Users Group, tell them about the project and ask if there
is anyone there that could perform the operation.  This modification will 
NOT hurt the computer in any way, unless it is installed WRONG.

You can make your own piggy back board or you can do what I am going to 
describe (since it is a little hard to put a schematic in a text file).

You should ground yourself with a static guard wristband (such as what 
Radio Shack sells).  Even though the chip is quite durable, just the right 
static discharge can ruin all or part of the SID chip.

For those of you that are not familier with the way pins are numbered on an 
IC chip here is a short explanation.  On one end of the IC you should find a 
little notch, looking at the chip with the notch at the top the numbering 
goes this way.  The upper left corner of the chip is pin 1 and they are 
numbered consecutively, counter-clockwise around the chip.  
Some chips do not have a notch in one end, but instead dot is placed in one 
of the chip corners to designate that pin 1 starts in that location.

            notch
          ----,,----
        1-!.       !-8
        2-! dot    !-7
        3-!        !-6
        4-!        !-5
          ----------


I have included the information that is needed to install this modification 
on the Commodore 64, 64C and 128.  I haven't been able to look inside the 
128D, so I cannot provide the information with any accuracy.

There are TWO different 64C circuit boards and both use DIFFERENT SID 
chips.  You can tell the difference by opening the 64C.  If you see a 64-pin 
chip on the board and the board is only 5.5-6 inches wide then you have 
the narrow board 64C and must use the 9 volt 6582 SID chip.  The number of 
the chip in the 64C narrow is an 8520 and is the same as the 6582.

----------------------------------

Parts Commodore 64, 64C (wide) & 128

1 - 6581 SID chip from Jamco or
    Kassara Microsystems
1 - 2N2222 transistor  Radio Shack
    276-1617
2 - 220pf capacitors  Radio Shack
    272-124

-----------------------------------

Parts Commodore 64C Narrow Board

1 - 6582 SID Chip  From Jamco or
    Kassara Microsystems
1 - 2222A transistor  Radio Shack
    276-2009
2 - .022uf capacitors  Radio Shack
    272-1066
2 - 1k ohm 1/4 watt resistors  Radio
    Shack 271-1321

-----------------------------------

Parts 64, 64C (all) & 128

2 - 1k ohm 1/4 watt resistors  Radio
    Shack 271-1321
1 - 1000 pf capacitor  Radio Shack
    272-126 listed as .001 mf this is
    the same as 1000pf
1 - 10k ohm 1/4 watt resistor  Radio
    Shack 271-1335
1 - 10 uf electrolitic capacitor  
Radio
    Shack 272-1025
1 - 5 inch length of wire
1 - 5 inch length of shielded cable
1 - surface mount female RCA plug 
(this
    is what you normally find on the
    back of your stereo.


On the C-64 and 64C (wide) the SID is IC U18 (the IC number will be marked 
in white on the circuit board).  It is usually located in the middle of the 
circuit board, next to the metal video chip case or up between and just below 
the serial and monitor jacks.

On the C-64C (narrow board) the SID chip is IC U9.  It is located in the 
middle of the board, just a little to the right of center) and called 8520.

On the C-128 the SID is IC U5.  It is located at the back of the circuit 
board just to the right of the metal housing for the 40 and 80 column video 
chips.

First bend out pins 23, 24 and 26 and cut them off of the 6581/6582 SID 
chip.  These are for the two analog and one audio input lines.  They will 
cause problems if connected and since they will not be used it is best to 
remove them.

Now bend out pins 1, 2, 3, 4, 8, and 27.

Solder one of the 220pf capacitors (64C narrow uses .022 uf) to pins 1 
and 2 then solder the other 220pf (64C narrow - .022uf) capacitor to pins 3 
and 4.  The capacitors control the upper and lower frequency range and 
filters of the SID chip.

The reason I am using 220pf capacitors is because of problems with the 
filters in the SID chip.  The C-64 first came out with 2200pf capacitors, 
but they were changed to 470pf.  The reason for this was because the 
filters of the SID vary from chip to chip and using 2200pf caused a lot of 
them to sound muffeled when the filters were on.  I have found that by 
lowering the capacitor value to 220 pf helps even more.  If you wish, you can 
use 470s if you feel it would be better, but DO NOT use 2200pf.

The 6582 SID chip for the 64C narrow must use the .022uf capacitors, as the 
filter range is much different.

Solder one end of your wire to pin 8 of the SID chip.  This is for the chip 
select line.  We will connect this to the cartridge port.  This tells the 
computer where in memory the chip resides (described later).

Now solder the remaining pins (excluding the ones we have bent out 
and/or removed 1, 2, 3, 4, 8, 23, 24, 26 and 27) to the sid chip currently 
in your computer.  You may have to bend those pins inward just a little 
for them to get a good grip on the SID chip.  Be very careful not leave the 
soldering iron on the chip TOO long as you could ruin BOTH SID chips.  I 
would put some heat sink (silicon grease) between the two chips before 
soldering them together.  This will provide better heat dispersal on the 
bottom chip.

Now that you have the chips soldered together (place the SID chips back in 
the socket if you removed them), solder the wire from pin 8 (on the SID 
chip) to pin 7 of the cartridge port on the back of the computer.  Set the 
computer infront of you like to are getting ready to type, with the back 
of the computer away from you.  Look at the cartridge port (located in the 
upper right corner of the circuit board).  You will see two rows of pins 
connecting the cartridge port to the circuit board.  You want the row of 
pins closest to the front of the computer.  Now, count the pins 
starting at the LEFT side and counting to the right.  You want to solder the 
wire from pin 8 of the extra SID chip to pin number 7 of the cartridge port.  
This is the same place on all of the models C-64, 64C and 128.

This will tell the computer that the extra SID chip is at address $DE00 hex 
or 56832 decimal.  You will access it just like you would the regular sid 
chip but starting at this address.

I am no longer describing how to connect for address $DF00.  This 
address causes problems with the RAM Expansion Units and numerous other 
cartridges.  From now on address $DE00 is the ONLY address for the SID chip.

Now partially reassemble your computer (be careful that nothing shorts out 
the pins still sticking out).  Turn the computer on and load the player 
program provided and tell it to load in 'TEST'.  If you get sound then so 
far so good.  Turn off the computer and disassemble the case.

Drill a hole in the back end of the computer just large enough to anchor 
the RCA plug.  Then solder the center wire of the shielded cable to the 
center post of the RCA plug.  Insert the wire through the hole you have 
just drilled and anchor the plug to the case.  Now solder the ground wire 
to the ground tab on the RCA plug.

Here comes the difficult part to explain.  This is the coupling circuit 
for the audio output.  Here is a rough schematic.



Pin 27 on             12volts dc, 
9volts 64C (narrow)
SID chip   resistor    !
--.          10k ohm   !collector
27!----.--/!/!/--.-----O 2n2222 or 
2222A
--'    !         !     !emitter
       !         !     !
       <resistor !     !
       >1k       !     ! +
       <ohm      !     :--!}---to RCA
       !         !     !  10 uf
       !         !     !electrol cap
       !         !     !
ground---        !     !
       -         !     <resistor
                 !     >1k
                 !     <ohm
                 !     !
                 !     !
                 !     !
                 !    ---ground
                 !     -
                 !
                === 1000 pf (.001mf)
                 !  capacitor
                 !
                ---ground
                 -


You can get the 12 volts (9 volts on 64C narrow) you need for the 
transistor directly from pin #28 of the SID chip.

If you need any help on constructing this circuit check out any of the many 
books that have schematics on the C-64 and/or 128.  This is similar to the 
one already inside the C-64 or 64C narrow.

The ground wire from the RCA plug can be soldered to the main grounding 
strip between the serial and video ports.  The center wire will be 
connected to the negative side of the 10uf electrolitic capacitor.

I still think you should have someone familier with electronics install this 
circuit for you.

If you have a problem with some cartridges, you will have to install a 
switch between pin #25 of BOTH SID chips.  This will CUT the power to the 
extra SID chip, effectivly turning it off.  I would suggest that you turn 
OFF the computer before you turn the extra SID chip ON or OFF with this 
switch.

A good place to mount the switch and RCA plug is on the back of the 
computer and above the monitor jack on the 64.  I still haven't found a GOOD 
place on the 128.  A suggestion was made that if you are not going to use 
the RF output on the computer, you can cut the wire going to that RCA plug.  
Then connect your audio output wire to the center connector of the plug.  
This does work but BE CAREFUL!

I have also provided a short player program to test the extra chip.  This 
program will play any SID song created but Compute!s SID EDITOR by Craig 
Chamberlain.  You can also use the STEREO.MODULE in your own software to 
play SID music.

Mark A. Dickenson
