ST4 DIY – Exp board
ST4 Expansion board (revisions h, i):
This board is the most complex. It has through-hole and SMD and a large variety of component packages.
Before we start, one very important fact. The PT8211 DACs vary wildly from batch to batch. This was unknown at the time of rev h and rev i design. R23 through R38 are normally 100k, but in case of PT8211’s that have reduced output range, you will need to solder 120k. This is the case with all the PT8211’s we purchased in 2016. You will also need to solder 130k for R1 instead of the old 100k. Of course, these are supplied in the kit.
The Bill Of Materials:
Let’s start with an high resolution overview of how the end result should look (click to enlarge). This is essential to figure out all the IC orientations.
It’s a good idea to start with the passives. This is the most work so let’s just get to it. Best to start with the biggest groups: 100n (at the head or tail of most IC’s) and the 100k and 50k (49k9) found in two columns left of center.
Proceed with the 100p’s which are required for the TL074 quad opamps IC1, IC2, IC3, IC4, IC5 on the left. Note that C43..C50 are 1n! Not all of those are marked on rev i. Sorry about that! The 2 small columns of resistors R39..R46 are 8k2 and are also without value on the silkscreen. These are found at TODO: red rectangle photo! R1 and R7 are 100k and are found at the left most part of the PCB.
Now for the IC’s.. It’s important to note that the silkscreens have double lines on the side of PIN1. There’s often no other way to discern the orientation. Beware!
Now the simple stuff: all the headers and socket.. Start with the male headers. This is how the bottom should look at the end:
Add the female headers for the Arduino’s SPI interface.
Now add the only IDC socket on the bottom. Mind the stripe which indicates where the gap should be!
Now solder all the IDC headers on the top side. Beware of all the silkscreen stripes. They indicate where the socket gaps should be!