LOLbooster Assembly

General Assembly Notes

Assembly of LOLbooster should take no more than two hours; experienced solderers may only require about 45 minutes. If you’ve ever soldered a decoder into a locomotive, you will find this kit a breeze to assemble. All parts are through-hole and relatively easy to solder. You will need the following tools:

• Soldering iron
• Flush-cutters
• Jeweler’s screwdrivers (flat-bladed and cross or Philips head)
• Heatsink compound (optional but strongly recommended; available at Radio Shack)
• Hobby vise (optional; for holding PCB during soldering)
• Multi-meter (optional; for testing)

The soldering iron need not be of high quality; An inexpensive model with a power rating of between 25W and 40W and a conical tip will suffice. A soldering gun, however, is inappropriate. Flush cutters are necessary for trimming leads after soldering. The screwdrivers are for attaching the heatsinks, wiring the screw-terminals, and adjusting the voltage-adjustment trimpot.

If you have little experience soldering, you will find that a through-hole kit, such as LOLbooster, provides a gentle introduction to soldering. Good soldering guides can be had on the internet, and a discussion of soldering technique is beyond the scope of this document.

In general, it’s a good idea to start with the shortest parts first, then move to taller ones. This is because it will likely be a real pain to try and fit, for example, the resistors that sit between the two heatsinks after the heatsinks have been fitted, because you’ll need tweezers. So we’ll start with the resistors, move to the capacitors, then the ICs and other components, with the two ginormous heatsinked ICs last.

Each part has a corresponding outline on the circuit board that shows how it should be placed. Match components and outlines by looking at the shape of the outline, and the value next to that shape. Oblong hotdog-like shapes are resistors; small rectangles and large circles are capacitors; large rectangles are ICs, etc. Each outline on the PCB also indicates the value of the part that should be placed there; if you know how to read the markings on each part, there will be no doubt as to which part goes where. (Look below for a guide to reading the markings on each part.)

List of Included Parts

The LOLbooster kit includes all of the necessary parts, except for hardware to mount LOLbooster to your layout, and a power supply. I figure you probably know better than I do how best to do that in your particular case, so I leave the particulars of the mounting to you.

Note that the identifier on each part may vary slightly from what’s indicated here: Manufacturers like to add suffices and prefices to the identifier, so that “LM358″ may become “LM358N”, or “74HC10″ may become “M74HC1081″. What’s important is that the stated identifier appear somewhere on the part; the stated identifier will never appear on a similar part of differing value.

Assembly

Here is a diagram of the top side of the bare PCB. Take a moment to examine the various markings, and to familiarize yourself with the layout.

Resistors

We begin with the resistors. The little blue (or sometimes beige or tan) cylindrical things are the resistors; the orientation does not matter, but the pretty colors do. Refer to the chart below to determine which resistor goes in which slot. Bend the leads at a 90º angle to the body, so the resistor looks like a staple, insert into the PCB, and then bend the legs outwards so as to hold the resistor in place while you can turn the PCB over to solder.

Note that some or all of the resistors in your kit may be beige or tan, rather than blue. This makes no difference.

Resistance	PCB Label	Appearance
120 ohms 1%	120R
1 kilo-ohm 1%	1K
1.1 kilo-ohms 1%	1K1
1.8 kilo-ohms 1%	1K1
3.16 kilo-ohms 1%	3K16
100 kilo-ohms 5%	100K
1 mega-ohm 1%	1M
10 mega-ohm 5%	1M

Once the resistors are soldered in, move to the resistor array:

Your resistor array may have different markings than the one pictured here. But one marking that is important is the brown circle, to the lower left. Resistor arrays are polarized. Pin 1 on the very left is indicated with the brown circle, because it is different than the other pins. Pin 1 should be soldered into the hole marked with a ’1′ on the PCB.

The second thing to notice is that although the circuit calls for a 3-element array (i.e. a array with 4 pins), your resistor array may have 4, 5, or even 6 pins. That’s just the result of market availability for resistor arrays of the size this board needs. The circuit board has extra holes to accommodate too-large resistor arrays. The important point is to make sure that pin 1 (i.e., the pin marked with the brown circle) goes into the marked hole (see the diagram).

Errata!

Mistaken silkscreen showing incorrect resistance value for resistor array.

Corrected silkscreen showing correct resistance value for resistor array.

Early versions of the REV B board mistakenly label the resistor array as “100R”, indicating a 100-ohm resistor array. In fact, you should use a 470-ohm resistor array, although the precise value is not critical.

 

 

 

 

 

 

Finally, solder in the trimpot. It’s the blue box thing.

Notice that there is an outline of the adjustment screw on the PCB. Simply align the actual adjustment screw with the drawing on the PCB to ensure that the trimpot is being installed correctly.

When you are done, the PCB should appear as such:

Ceramic Capacitors

LOLbooster uses two different kinds of capacitors: Ceramic, which look like this:

and aluminum electrolytic, which look like this:

Begin with the ceramic capacitors. If you have trouble reading the values on the capacitor bodies, the value should also be written more legibly on the polybag each is packaged in. Notice that the units on the polybag label and the units on the PCB may not match up: Consult the table below to see the different ways each capacitor might be marked.

Ceramic capacitors are unpolarized, and so orientation doesn’t matter. Thread them into the correct holes, and bend the legs outward to hold them in place, as before.

When you are done with the ceramic capacitors, your board should look like the one above.

Aluminum Electrolytic Capacitors

The aluminum electrolytic capacitors are polarized, and orientation does matter. The PCB is marked with a “+” sign to indicate where the positive lead should go. The positive lead is the longer lead. Notice also that the capacitor has a stripe along the side indicating the negative lead. It is very important that these capacitors are installed with the proper orientation, on pain of explosion. Ouch.

The values on the side of the capacitor should match the values printed on the PCB.

When you are done, your board should look like this:

LEDs

LEDs are polarized devices, and as with the electrolytic capacitors, the long lead indicates the positive lead, and a flat side to the lens indicating the negative lead. The PCB is marked with a “+” sign next to the positive (longer) lead, and an outline indicating the flat for the negative lead.

The green LEDs are for the two power indicators, and the red for the two warning indicators. When you are done, the board should look like this:

Chip Sockets and Chips

Most of the chips (those with two rows of pins) will not be soldered directly to the board, but will be inserted into mating sockets which will be soldered into the board. Notice that the chips, sockets, and PCB silkscreen all have a semi-circular notch at one end. Make sure that these are aligned when soldering the sockets and inserting the chips!

The boad will look like this once the sockets are soldered in.

Then identify the following four chips. Note that the identifier on each part may vary slightly from what’s indicated here: Manufacturers like to add suffices and prefices to the identifier, so that “LM358″ may become “LM358N”, or “74HC10″ may become “M74HC1081″. What’s important is that the stated identifier appear somewhere on the part; the stated identifier will never appear on a similar part of differing value. The “SFH6731″ has funny-shaped legs, which may help in identifying it as the printing may be quite faint on this chip for some reason. (Also note that the SFH6731 does not have a semi-circular notch in one end of the package; instead, it has a printed dot at one end that serves the same purpose. Go figure.)

To insert the chips, the pins must first be straightened to 90 degree angles. Set the chip on its side on a flat surface, and gently but firmly roll the chip so that the pins flatten out to a right angle. Repeat on the other side.

Once the chips are in, your board will look like this:

Terminal Blocks

Next, insert and solder the terminal blocks such that the terminals face outwards, towards the edge of the PCB. The angled terminals are used for the inputs and ground terminals; the vertical block is used for the DCC out terminal.

More Chips

Next identify the two chips below, again recalling that the identifier may including one or more suffix or prefix characters.

The L7805 needs the teeny-tiny heatsink. If you have some heatsink paste, apply a very thin layer to the back of the L7805. Place the heatsink so that the fins face forwards (see illustration below), then thread the bold from the front of the chip (the face with the printing on it), and through the heatsink. Place the locking washer and nut on the heatsink side, and tighten the assembly until hand tight.

Did you insert the bolt as indicated? Double check, because if you inserted the bolt the wrong way, you have no way of removing it if it came to that.

Then insert both the L7805 and the STPS745 so that their shape matches the outline on the PCB. Both are polarized, so take care to insert them correctly. The two-legged chip will face outwards, and the three-legged chip will face inwards. Take care that the metal tab of the STPS745 and the heatsink on the L7805 do not come into contact.

Yet More Chips

The final two chips are the trickiest, as they must be first mounted to the ginormous heatsinks. Identify the two chips below, yet again recalling that the identifier may including one or more suffix or prefix characters.

Attach the heatsinks to each. If you have some, smear a thin layer of heatsink compound along the back of each chip. Thread the bolt through the narrow channel of the heatsink, then through the chip. Slide the lock washer onto the bolt (the lock washer should be against the chip, and not the heatsink), and then loosely screw the nut in place. Do not tighten yet, but seat the loosely assembled chip into the PCB.

Did you thread the bolts as indicated in the text above? Really? Double check, because if you threaded them the opposite way, you will have no way to tighten the bolts once both chips have been soldered in place. So check again.

Flip the PCB, letting it rest on the top of the heatsink, and while hold the PCB flat against the heatsink, solder the chip’s leads and the solder lugs on the heatsink. Because they are attached to a heatsink, the solder lugs will take a fair amount of time to heat up in order to solder them securely to the PCB; do not assume the chip is strong enough to support the heatsink without having to solder the lugs, becaue it isn’t. Just be patient and don’t worry too much about overheating the attached chip. Repeat with the second chip.

Now tighten the bolts until hand tight.

Below is how your completed LOLbooster should look when you are finished:

Final Touches

Finally, use the mounting holes (which are sized to take a no. 4 screw or bolt) to attach LOLbooster to the underside of your layout, or where ever you would like to locate it.

And now your LOLbooster is complete!

Click here for installation instructions.

Some images in this document are derived from the Fritzing Project.

“LOLbooster REV B Assembly” by D.E. Goodman-Wilson is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.