ASSEMBLING THE BOARDS
Take your time stuffing components into the boards.
Follow the parts list and schematic for a description of where each part
goes. Each of the boards has it’s own separate numbering system for designators.
For instance, designator R-1 appears on each of the 6 PCB’s. The same applies
to capacitors, transistors, and headers, so always check the parts list.
If you have a question or believe the documentation may be in error, PLEASE
contact us either by e-mail or via the message board.
One of the biggest pitfalls in assembling the boards
is getting the correct value resistors where they belong. Check the web
site for the resistor color tables to make certain you have the correct
value. Sometimes it is hard to decipher the color bands on a resistor or
misread them. Double checking resistor values with an ohmmeter is a quick
way to ensure the correct value is in the right place. Checking your work
carefully at this stage will save hours of troubleshooting headaches on
the back end. You'll learn this from experience. The web site contains
photos of finished boards to use for visual reference.
WATCH THAT DECIMAL PLACE
Be extra careful with resistor values when stuffing
the side-chain board. There are a lot of resistors that can easily be mixed
up because their significant digits are all the same but the decimal multipliers
are not. There are 475, 4K75, 47K5 and 475K values for the various ratio
settings. See how they are all related by a factor of ten? Also note that
as often as possible we use the European style of substituting the magnitude
— a K or an M — in place of the decimal, which could easily get "lost"
in the printing process. It's amazing how a spec a dirt might even be misread
a s adecimal place if it lands in the right place.
Also, capacitors C-6 and C-7 of the side-chain PCB
have different footprints on the boards than the parts on the parts list.
C-7 is a .01 cap that will need its leads bent out slightly to fit into
the holes. Carefully bend each leg with your needle-nose pliers close to
the base of the cap. Then move the pliers down a few millimeters and bend
the leads back in a bit so they point perpendicular to the board. This
is done to widen the base of the cap to fit in the holes. Be careful to
not break the base of the cap by bending too hard or too much when making
the first outward bends.
Conversely, C-6 will need to be bent in the opposite
direction to shorten the base. Bend the leads inward close to the base
and then slide down and bend them out again to make them perpendicular
to the base.
See the images below for a visual reference.
Hopefully you have already marked and drilled
mounting holes on the chassis bottom before the boards were stuffed as
indicated earlier in the instructions. Now the boards can be mounted to
the chassis via stand-offs with screws through the bottom of the chassis.
The next step is to connect the boards. The most
important thing to get right is the power distribution. Check the schematics
and note that the header pin-outs at the power supply do not match
the receiving power pin-outs at each board. Note that pin-1 and pin-2 on
each input power header is ground. The power supply output headers have
only pin-1 as ground. The extra ground on the receiving PCB’s is there
for a convenient ground tap when connecting switches, or extra boards.
You probably won’t use them all, but be aware of their existance and intended
Hooking the –10volt and/or +30volt rails to the one
of the ground pins can damage the FET’s and transistors on the boards as
well as cause damage to the power supply.