The XTB has a densely populated circuit board. Assembly requires experience working with small components, and the ability to correctly identify component values.  A low-wattage soldering iron with a 1/8" or smaller tip is recommended.  Care must be taken to properly align the tiny surface-mount op-amp before soldering, and the semiconductor devices should not be overheated.  Several components have been packaged separately because identification can be difficult.  Please be careful not to mix components from the different packages together.

BEFORE ASSEMBLY

DO NOT MIX UP THE COMPONENTS.  A few people have had trouble identifying some of the components.  Several components have been packaged with the semiconductors to help identify them.  Those include the two tiny Pico fuses and zener diode D9.  It is best to keep them packaged until you are ready to install them.  If you have trouble identifying any components, please refer to the detailed parts list with physical descriptions at the end of this document.  That will be helpful to those of you who may not be familiar with manufacturer coding or resistor color charts.

PRINTED CIRCUIT BOARD ASSEMBLY:

Please read the Detailed Assembly Instructions below before beginning actual assembly.

The photographs in this document were taken for the Rev 1.0 PCB.  Several minor changers were incorporated into the Rev 1.1 PCB.  Since none of the changes significantly affect the assembly process, the photographs not been updated.  Please refer to the layout below if one was not included with your kit:

Printed Circuit Rev 1.1 Layout Diagram.

NOTE:  An additional bandpass filter has been added to the XTB to help deal with powerline noise.   This was implemented by changing a resistor to an inductor, eliminating one resistor, and two value changes.  Some kits may have R14 at 5.1 ohms, which gives a slightly narrower bandwidth.  Please note that the photographs do not include this change.  Be sure to refer to the parts list at the end of this document and the comments in the assembly order below.  Contact me if you need the assembly notes and parts list for the earlier version.

Do not try to assemble the XTB with a high wattage soldering iron having a tip larger than 1/8".  I use a variable temperature iron with a 1/16" tip.  After assembling over 100 XTBs myself, I recommend installing components in the following groups:

D10, D11, D12, D13
D1, D2, D9  (D9 is from the semiconductor pack)
R2, R9, R15
C3, C9, C6  (C6 was changed in value for the filter)
R6, R5, R14, R4, R16  (R14 was changed for the filter to 5.1 or 10 ohms)
U1
D4, D3, D7, D8  (Only D8 band down, others band up)
L5 (install @ R13), R3  (L5 is for the new filter, R12 was deleted)
R10, R11, D5, D6  (Only D6 band down)
C7  (bar or + sign near D5)
C1, C2, C4, C5, MOV  (Some MOVs are too tall, and must lean out to clear the transformer)
F1, F2  (from the semiconductor pack)
R1, R8
L1, L2
L3, L4  (skinny end up)
Q1, Q2
Q3  (metal tab toward board edge)
R7
C8  (check polarity)
Transformer  (2 pin primary facing C4 & C5)
LED  (long pin at +)

DETAILED ASSEMBLY INSTRUCTIONS:

Many components stand on end in order to fit into the available space.  This should make it easier for the DIY builder to assemble the XTB than if it had used smaller surface-mount devices.  The size of the board is determined by several major components that are not available in surface mount packages anyway.  Be careful when installing diodes because the banded end must be at the pad labeled "K" in the layout diagram accessed by clicking the link above.  The "K" does not appear on the silkscreen, but that pad will have an extra circle around it for identification.  Most of the diodes mount banded end up, but D6 and D8 mount banded end down.  You can verify correct diode polarity by comparing with those installed in this photograph if unsure.

Note that the added bandpass filter requires substituting inductor L5 for resistor R13, and eliminating R12.  The inductor is normally blue or green, and will measure approximately 5 ohms.

Install the smaller devices that are flush to the circuit board first.  Use caution not to accidentally mix up zener diode D9 with one of the 1N4148 diodes.  They are the same color, and almost the same size.  The zener may be very slightly larger, and is packaged with the last group of semiconductors to be installed.  If these do get mixed up, it takes a strong magnifier to read the part numbers on these tiny devices.  Work your way up to the larger passive components.  The small ceramic capacitors may vary in size and color depending on the manufacturer.  Be certain that the 0.22uF is installed at C3.  Also be careful not to confuse the Pico fuses with the resistors.  They are similar in size, and magnifier may be needed to read the current ratings.  The Pico fuses are packaged with the semiconductors to make identification easier.  They may look identical to each other, but they have different current ratings.  Be careful to install them in the correct locations.  The higher current fuse should be installed at F1.  There are extra pads for some of the capacitors to accept alternate devices with different lead spacing.  When supplying your own components, please verify alternate devices will fit into the space available before ordering.  Be sure you install the two polarized capacitors correctly.  The little tantalum C7 is installed with the bar or + sign to the right near D5.

The op-amp should be installed near the end to reduce the chance of static damage, but it is easier to install before the other passive components that surround it.  The op-amp is located with pin 1 (tiny dot) near D8.  A technique that works for me is to carefully position it over the pads and hold it in position while just touching the tinned iron to one corner pin.  If alignment isn't perfect, that pin can be reheated and the position adjusted slightly until the pins are centered on the pads.  Then using just a quick touch, solder the pins using the barest amount of solder to avoid bridging the connections.  Be very careful not to overheat.  When you are done, check the quality of these connections with a magnifier.  This is certainly the most delicate operation of the entire assembly.  The op-amp is available in DIP and T05 versions, but there was just no way to squeeze these larger devices into the space available.  Install the transistors and power FET near the end because of their sensitivity to static damage.  Be sure to orient the transistors and FET to match the marking on the silkscreen layer.

The transformer should go on next to last because of its size and weight, followed by the LED.  The transformer can have 6 or 8 pins.  CAUTION:  The primary winding (2-pin side of a 6-pin transformer) is positioned near C4.  Transformer pin 1 (possibly marked with a dot) goes into the hole with the square pad near the MOV.  The transformer may be a tight fit, and should be pressed firmly down onto the printed circuit board until its plastic base is seated.  Be careful not to flex the printed circuit board during this process so there is no danger of damaging other components.

The LED is mounted full-length with sleeving over both pins.  The parts kit should contain a 2" length of clear sleeving.  Cut that exactly in half and trim slightly so the shortest lead extends just through the circuit board.  The longest lead goes into the + pad.  If the cover isn't pre-drilled, drill a matching hole in the cover 1/2" up from the bottom, and 5/8" in from the side.   A 3/16" hole will keep the LED recessed inside the cover, and a slightly larger hole will allow the LED to pop through.  When the cover is installed, the LED should be angled to face up into that hole.

INTERWIRING & FINAL ASSEMBLY:

IMPORTANT:  The Polycase base must be modified to prevent conflict between the XTB circuit board and the internal extension of the AC plug ground pin.  That extension will be removed from bases shipped with XTB kits.  If your base has not been modified, use a rotary tool with a small cutoff disc to remove the internal extension of the ground pin so that it is flush with the plastic base.  It was impossible to create a layout that provided enough clearance so the ground pin extension did not have to be removed.  I don't know why Polycase did this, as it is clearly not required for any mechanical purpose.

The AC receptacle should be pressed into the opening in the Polycase cover with the same alignment as the plug on the base.  The receptacle may not lock in securely unless a screwdriver is used to force the plastic tabs slightly outward until they click into place.

Six connections go to the AC sockets.  The 8" green wire supplied with the kit will run directly between the ground pin on the plug and the ground pin on the socket.  While not necessary for proper operation, this connection should be installed for safety.  Insulate the plug ground tab with shrink sleeving to keep it isolated from the printed circuit board.  The parts kit will include short pieces of 1/8 and 3/16 shrink sleeving to double insulate the ground tab.  Keeping the ground tab flush with the plastic base, the ground wire should be looped back on the left side of the case, and around the left plug pin on the way to the top cover.  Be careful not to melt its insulation when later soldering that pin.

The remaining wire should be cut into 4 pieces:  3", 6", 6", & 7".  Strip 1/8" from one end, and 1/4" from the other end of each of these wires.  Tin both ends.  The short end of each wire is soldered to the printed circuit board as follows:

        3" at the right COM hole near the large capacitor ground lead
        6" at the left COM hole near the large capacitor ground lead
        6" at AC hole near L1
        7" at X10 hole near L2

Make sure all leads are cut very close to the circuit board, especially in the area around Q2 to provide maximum clearance for the ground tab when the printed circuit board is mounted.  The board mounts to the base with 4 screws.  The double insulated portion of the ground lead will be compressed slightly when board is mounted, but that portion of the circuit board contains no solder connections.  Make sure the ground lead itself is routed off to the side, and that no solder connections along its path have sharp points that could pierce the insulation.  If you wiggle the ground lead slightly as the board is fastened down, it should position itself between points of compression.  The wire included with the kit is rated 600V, and most active circuitry is operating near ground potential when properly wired.

After the board is mounted, the AC connections are made as follows:

Check the AC & X10 connections because the XTB will not work if they are reversed.  Carefully push excess wire going to the AC connectors into the free space inside the cover, and mount the cover with the LED angled to be visible through the hole.  Add the 24-watt warning label to the cover just above the receptacle, and the XTB label to the recessed portion on the back.

TEST & OPERATION:

As a final check before applying power, verify the resistance between the two plug prongs is about 160 ohms.  If it reads much lower, the transformer may have been installed backwards.

Once assembled, plug it into an AC outlet with a manual X10 controller plugged into the receptacle for testing.  The LED should only flicker when the XTB is amplifying an outgoing X10 signal.  The LED will not be illuminated all the time like the one on the TW523/PSC05.  If the LED is ever illuminated constantly, please unplug the XTB immediately.  That means a fault condition exists that must be resolved.  It might occur if the XTB is plugged into a receptacle without a X10 transmitter connected.  If the LED does not flicker at all, then it is likely something is wired wrong.

The X10 input receptacle will supply 24 watts maximum.  That is about 10 times the average current drawn by a typical X10 controller.  The Rev 1.1 board contains a 3/8A Pico fuse (F2) between L1 and L2 that will pop if the 24-watt limit is exceeded by even a small amount.  That should never happen when the XTB is used for its intended purpose.  Obviously, the cause of the fault should be found if either of the fuses must be replaced.  While not recommended, a popped Pico fuse could be replaced by a single fine strand of wire from a length #18 flexible lamp cord.  To offer protection, that #18 lamp cord should have at least 40 fine strands of wire.  Form that into a loop away from the printed circuit board before soldering.  X10 modules use a similar inexpensive wire loop for protection.

CONVERSION TO 240V OPERATION:

It is feasible to modify the XTB for 240V operation, but it is recommended that the XTB-IIR be selected for 240V applications.  The transformer must have a dual primary for 240V operation, and the appropriate jumper installed to connect the primaries in series.  C1, C2, C4, and C5 must all be 400V versions, which are tough to squeeze into the available space.  The fuses must also be rated for 250V, which again are much larger.  The most difficult items to deal with are the standard 120VAC connectors on the base and cover.

Please contact me if you have any questions at: jeff@jvde.us
If you don't receive a response within 24 hours, try: xtbjeff@gmail.com