XTBM Assembly Notes
01/25/10   (version 1.1 PCB)

Please check for the latest version before beginning assembly.

The XTBM should be a relatively easy PCB to assemble.  Because some locations are left unpopulated, please refer to the parts list.  Assembly requires experience working with small components, and also the ability to correctly identify component values.  A low-wattage soldering iron with a 1/16" tip is recommended.  Care must be taken to not overheat the semiconductor devices.  Several components have been packaged separately because identification can be difficult.

BEFORE ASSEMBLY

A few people have had trouble identifying components.  The zener diode is packaged with the other semiconductors to help identify it.  It is best to keep it packaged until you are ready to install it.   You will need a magnifier to read the some of the part numbers.   Be sure you have correctly identified ALL the diodes before you begin installing them.  I also recommend sorting out the capacitors and resistors before soldering any onto the board.  Be careful to distinguish between 3.3K and 33K 5% resistors, and 1.0K and 10K 1% resistors.

PRINTED CIRCUIT BOARD ASSEMBLY:

Please read these Detailed Assembly Instructions before beginning actual assembly to avoid any problems.  Also, please refer to the parts list, board layout, and high resolution photograph of the assembled board while assembling your own unit:

XTBM Parts List

XTBM Version 1.1 Board Layout

XTBM Version 1.1 Board Photograph

Do not try to assemble the XTBM with a high wattage soldering iron having a tip larger than 1/8".  A variable temperature iron with a 1/16" tip works well.  I recommend installing all diodes first, followed by the 1/4 watt resistors.  Work your way up to larger and larger components.  Leave the transformer for last.

A dual-primary transformer may be supplied with the XTBM.  That can be identified by it having 4 pins on both sides.  A dual-primary transformer requires two short jumpers to be installed on the reverse side of the board to connect the primaries in parallel for 120V operation.  The connections are diagramed on the silkscreen.  Cut-off component leads can be used for both of the short jumpers.  Be sure to cut these leads flush with the top surface of the board so they don’t interfere with the transformer.  Note that for use on 240V, both windings must be connected in series with a single jumper.

Things to watch out for:

1)  The 1% resistors are blue.  They follow the standard color code, but the tolerance band is brown for 1%.

2)  The small 220uH inductor L3 may be blue or green, and looks like a resistor.  It can be identified by its resistance is being about 6 ohms.

3)  C3, C16, and C17 are polarized capacitors.  Be very careful to get the polarity correct.

4)  The 8.2uH inductors are a tight fit.  I recommend installing them with the wider section at opposite ends, as shown in the high-resolution photo.

5)  IMPORTANT:  Q2 2N7000 is static sensitive, and is very easily damaged.  R14 was changed to zener diode D13 on the version 1.1 PCB to protect Q2 when the microcontroller U4 is not in the socket.  Be sure D13 is on the board before installing Q2.

6)  Be sure U5 is firmly seated because it is a tight fit under the cover.  It can be bent slightly toward the rear if it still contacts the cover.

7)  The PCB and LCD display accept a 16-pin connector.  Pins 15 and 16 are only used for a backlit display, and 14-pin connectors are normally supplied.  Be careful to install those connectors at the pin 1 end of the hole pattern.  The male header goes onto the board with the LONG end up.  The female socket is soldered onto the LCD facing down.  Before soldering all pins, make sure both connectors are aligned exactly vertical so they will mate when the cover is installed.

8)  There is no extra clearance between the transformer and the top cover.  Be sure the transformer is firmly seated to the PCB before soldering it down.  If you have installed jumpers for a dual primary transformer, be sure they are snipped flush with the top of the PCB.  The jumpers are not needed unless the transformer has a dual primary (8 pins).  Depending on the transformer manufacturer, the pin numbers may be labeled on the bobbin near the pins, or there may be a mark at pin 1.  Pin 1 goes in the square pad near D6.

9)  You will note that a number of device locations are not populated.  They were there to provide some “just in case” options for the first production board.

10)  When installing the power cord, allow a little extra wire for the bend in the strain relief before squeezing it closed.

11)  The LCD display mounts to the top cover with the supplied self-tapping screws.  While a tight fit in the LCD display, they are the ones supplied for that purpose.

12)  Since there is not much clearance under the board, all leads must be cut short – certainly no longer than 1/8” above the board.

13)  I originally planned to rigidly mount the PCB to the base with screws and cup washers.  However, it seats firmly enough that rigid mounting is not necessary.  It is held in place by the LCD connector and the power transformer.  Just push the PCB down until it sits on the flanges around each of the holes for the case clamping screws

XTBM CHANGES FOR 240V 50Hz:

R18 is 330K 1/2W, and MOV1 is 275V for the 240V version.  Also, C1 and C5 must be rated for 600VDC or 250VAC

The transformer primaries must be wired in series for 240V with a cut-off component lead.  (use the small holes).

RECOMMENDED ASSEMBLY ORDER:

D1, D2, D3, D4, D5 (all 1N4148)

D6, D7, D8, D13  (BAT43 & zeners)

Add 120V transformer jumpers on back if transformer has a dual primary (8 pins)

    NOTE:  for 240V install single jumper as shown.

    NOTE:  snip jumpers flush with top of board before installing transformer

R7, R10, R22, R20, R21, R23, R24, R19  (all 1/4W 5%)

R26, R17, R2, R3  (all 1/4W 5%)

R5, R6, R8, R11, R9, R15, R16, R13, R12  (all 1/4W 1%)

    NOTE:  no 1/4W resistors should be left

L3, R1

D9, D10, D11, D12

R18, R4

DIP socket for U4

U1, U2, U3  (dot near the square pad & be sure U2 is AD817)

2-clips for Fuse  (be sure to orient so the fuse can snap in)

F1  (do it now so you don’t forget)

C6, C7, C14, C13, C12, C11, C15

C20, C19, C8, C9

C4, C2, C18, C21

L1, L2  (with fat ends opposite)

TS1  (install facing board edge & make sure it is fully seated)

C5, C1, C3, MOV1  (be sure of C3 polarity)

    NOTE:  C5 may be a high-voltage ceramic for the 240V version

carefully install Q2

J1 14-pin header  (starting at square pad with long pin side facing UP)

    NOTE:  make sure it is fully seated and exactly vertical

Q1

U5  (large 5V regulator - be careful not to confuse with Q1)

C16, C17  (be sure polarity is correct)

X1 Transformer  (pin 1 at square pad, make sure jumper(s) are installed if required)

Plug in the PIC microcontroller U4

Install J2 14-pin socket on LCD assembly  (starting at pin 1 end, and facing DOWN)

    NOTE:  make sure it is fully seated and exactly vertical

INTERWIRING & FINAL ASSEMBLY:

Install the power cord through the rear panel with the strain relief.  Be sure to leave enough slack to make connections to the terminal strip.  Orient so the polarized plug wide prong connects to the neutral terminal on the terminal strip.  Press the PCB down onto the base and slip the back panel into the groove.  Before mounting the LCD assembly to the top panel, plug the it into the header, and apply power.  Be careful because there is 120V inside the unit.  The LCD should indicate the unit is functioning.  If your unit indicates FAIL SELF TEST, carefully check your assembly.

Assuming the unit is working, remove the plastic protection from the LCD and mount it to the top cover with the screws provided.  They may be a tight fit through the LCD PCB.  Using the back panel as a guide, carefully install the cover.  If the connectors were mounted exactly vertical, they should mate without a problem.  You can look in through the side to check orientation.  This is perhaps the trickiest part of the assembly.  (One fellow found it easier to mount everything to the cover, and then slip on the base.)  Install the rubber feet and label to the underside if they are included in your kit.

TEST & OPERATION:

If you have a Maxi Controller, plug both the XTBM and Maxi Controller into the same receptacle.  If there is no signal sucker on that circuit, the XTBM should display voltage above 5Vpp for the Maxi Controller commands, and the decoded commands should be displayed.

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