How to succeed with your clock

Go step by step, following the instructions and performing ALL the tests.

If one of the tests fails, DONT KEEP GOING! Stop, try to get the test working again and post in the forums if you're stuck. If you keep going it will not magically fix itself and you'll have much more to try to debug...
Get ready by checking all your parts against the Bill of Materials (parts list). Once you are sure you have everything, prepare your workspace by heating up the soldering iron, wetting the sponge and arranging your tools and parts so they will be convenient.

The first part to be placed is the DC jack. This connector allows you to power the clock using an external power adapter.

Place the part as shown, it will only be able to fit in one way.

Now flip the board over. If the DC jack doesn't stay in place, you can use a piece of tape to hold it against the PCB, or use a finger if you are dexterous.

Now using your hot soldering iron, press the long side of the tip against the one of the pins and pads for the DC jack. Wait a few seconds until they are heated up and then press solder into the connection so that it flows into the entire pad.

Repeat for all three pads. Make sure there is plenty of solder filling the holes completely, they provide mechanical strength!

The second part to go in the fuseF1. The fuse looks suspiciously similar to a ceramic capacitor. So before you continue lets identify the fuse.

The fuse, all the way on the left, is yellow and has a larger 'head'. The leads have a kink in them and the lead spacing is wider than the capacitors, 0.2" (5mm)

Once you have picked on the correct part, place the fuse next to the jack. Remember it should just fit, if you have to bend the leads a bunch you may have picked out a capacitor. Fuses are just 'wires' so they can go either way and work fine. The fuse protects the circuit, when the circuit tries to draw more than 200mA, the fuse heats up and cuts the power to the circuit. After a whilewhen it cools down, the fuse resets and passes current to the clock again.

The fuse will sit 'above' the PCB when placed correctly. This makes sure there is plenty of air circulating around the part so dont try and squish it against the PCB all the way

With the leads bent, the part will stay in place. Flip the PCB over.
Now using your soldering iron, heat up both the pad and pin of the component and apply solder. Do the same for the other leg.
Next it is time to clip the extra long leads of the fuse. Using your diagonal/flush cutters, clip the wires right above where the solder joint tapers off.

Next is the input protection diodeD1 and D2. Diodes are a semiconductor component that only allows current to go one way. By placing a diode between the power input and the circuitry, it helps protect against plugging in a negative DC power supply (backwards) which would make the kit release its 'magic smoke'. As you can imagine, its important to place the component in the right way. On one end of the diode is a white/silver stripe. Make sure this stripe matches the stripe in the silkscreen image. See the image left if you're not certain.

Bend each diode into a 'staple' shape and once you've double-checked the polarity, place the diodes in the D1 and D2 spots. Then bend the leads out a little so that the diode stays flat against the PCB.

Now using your soldering iron, heat up both the pad and pin of the component and apply solder. Do the same for the other legs.
Next it is time to clip the extra long leads of the diode. Using your diagonal/flush cutters, clip the wires right above where the solder joint tapers off.
Next is the 7805 5V regulator chip IC3. This component takes the voltage from the power adapter, which can be from 7V to 16V, and reduces (regulates) it dow to a nice smooth 5V. Bend the legs into a 90deg angle...

And then lay the part down so it matches the silkscreen. Try to get the hole in the regulator's metal tab to line up with the hole in the PCB. you can make this a little easier by taking a 4-40 screw (such as those in the enclosure kit) and placing it through both holes to line them up.

Then to keep it in place, solder one pin of the 7805 from the top.

Once you have the 7805 tacked in place, flip over the board and solder in the three pins.
And clip them short.

Next is C2, the 47uF/25V electrolytic capacitor. This capacitor smooths out any large ripples in power coming into the kit. Electrolytic capacitors arepolarized which means they must be placed correctly or they wont work at all. If you look at the capacitor you'll notice one leg is longer than the other, this is the positive (+) lead. Make sure this lead goes into the pad silkscreened with a +. See left for how to place the capacitor.

Next is C4, a 220uF/6.3V electrolytic, which is the capacitor which helps reduce noise on the regulated 5V supply. It is electrolytic so make sure its placed correctly.

Once the electrolytic capacitors are placed correctly, bend out the leads and solder them in place.

Use the diagonal cutters to clip the leads short.

Now place C1 and C3, both 0.1uF ceramic capacitors. Make sure to use the 'plain' 0.1uF capacitors. These don't have kinked leads (middle in the lefthand photo).These capacitors are smaller and work with C2and C4, smoothing out smaller high frequency noise. Ceramic capacitors are not polarized so you can put them in either way!

Bend the leads, solder and clip.

Now is a good time to take a break and test your work so far. Place the board down on a clean surface - make sure there are no stray wires or solder balls, etc.

Plug in a DC adapter that provides 7VDC-12VDC and at least 200mA, positive tip. (See this tutorial on how to verify your adapter)

Now find your handy multimeter, and set to measure DC voltages (and set the range if necessary).

Place the ground/black probe on the big silver tab of the 7805 (which is a ground connection). Then place the tip of the positive/red probe on the first pin of the 7805 (closest to the 'bottom', as shown in the image).

You should get a DC voltage between 7V and 13V. If not, check: is the adapter plugged in? Are the diodes correct? Is the multimeter hooked up right and in the right range?

Now check the 5V regulator by probing the third pin (closest to the 'top' in this image). You should get a steady voltage between 4.7V and 5.2V DC

If the voltage is not right, check the components such as the electrolyic capacitors, and IC3 now.

Make sure you have the 5V supply working now, since it is an essential test!

Unplug the board as soon as you are done, do not solder while the board is plugged in.

We will now continue and place the 270K resistor R1, this resistor is part of the 'lost power' detection circuitry. Resistors are nonpolarized so they can go in 'either way'. Bend the part into a staple and place it over the silkscreened R1.

Also place the piezo beeper SPK. This is the alarm noise-maker! It is non-polarized and can go in either way.

Solder in both components and clip the leads.

Now place the IC socket. The socket protects the microcontroller chip and allows it to be replaced if necessary.

The socket has a U-shaped notch in one end. Make sure that this notch matches the U-shaped notch in the silkscreen, see the image to the left if you're not sure. If you end up putting the socket in backwards, don't fret. Its not essential that it is in right, but it will help you if you have to replace the chip.

You can keep the socket in place with tape or if you have long fingernails, by bending over two of the little legs to hold it in place. First solder in 2 opposite corners. Then solder the rest of the pins.

They do not need to be clipped as they are already quite short.

Now it is time to insert the chip! Carefully remove it from the packaging. You'll have to bend the pins in a little to make them fit nicely into the socket. I grab both ends and rock the pins against a tabletop. (The image shows a smaller chip, but the idea is the same). Once the legs are parallel, locate the U-shaped notch in one end. Make sure that this end goes into the notched-end indicated on the silkscreen (and, hopefully, the socket as well)

Double check the chip is in right!

Now making sure that all the legs are lined up, and not bent or twisted, press the chip into the socket. It should seat itself easily without a lot of force.

Now we will do another quick test. Clear off the table and plug in the board. You should hear the piezo beep. If it does not, check the 5V regulator, make sure the chip is in right, and that R1 is in the correct location.

We'll now finish the low voltage power detection circuit. Solder in the 100kohm resistor R2 (this forms a resistor divider with R1) and 0.1uF capacitor C10 which keeps the resistor divider voltage steady.

Solder and clip the parts.

Solder in the 10K resistor R5. Photos to come soon. This resistor is next to R1 and R2 you just placed. Bend the 10K resistor over, as shown in the image to the left, and solder in place.

Now we will place the 32.768 khz clock crystal. This crystal lets the chip keep time properly. The crystal Q1 is a silver tube and is symmetric so it can go in either way. Next to it goes two 20pF capacitors C8 and C9. These caps stabilize the crystal to keep the timing correct. They are ceramic capacitors but are in a disc package. They are symmetric and can go in either way.

Solder and clip the parts.

Please note that a few people have had clock difficulties because they put the 20pF capacitors in wrong. They'll fit if rotated 90 degrees so DOUBLE CHECK that the caps are in right!

The 20pF capacitors might also be blue colored instead of orange!

Now we will begin to build the boost converter that generates the 60V for the VFD tube.

Place 47uF/25V capacitor C7Make sure to place it correctly as it is a polarized capacitor.

We also need to place the high voltage transistor that does the switching in the switching regulator. Its a little confusing how to place it because there is no notch. However, two of the pins are bridged. These go on the right as shown.

Place the transistor chip solidly against the PCB.

Next place another Schottky diode D3 as shown, make sure the stripe lines up properly.

Also place the large 100V capacitor C6 (its the large round thing) which smooths the output of the boost converter. Make sure to place it correctly as it is a polarized capacitor.

Next is the inductor L1 which stores and releases power to boost the voltage up. Inductors are just coils of wire so they are not polarized and can go in either way.

Solder in all of the components.

The diode connects directly to the transistor at one point so it may seem like a short but it is done on purpose.

Clip all the leads.

Now place the 60V zener diode D5. The zener diode, unlike the other diodes, is not black with white stripe but rather red glass with black stripe. Make sure the stripe on the glass diode matches the white stripe on the silkscreen.

Solder and trim the leads

Now it is time to test the boost converter.

Clear off the desk and make sure there are no stray wires hanging around. Plug in the board and be careful not to touch the right hand side of the PCB. If you need to hold the PCB, hold it by the left hand side near the DC jack. This way you will not risk touching the boost converter. Use a nonconducive vise if necessary.

Set up your multimeter to measure around 60VDC. Touch the black (negative) lead to the ground tab of the 7805 and the red (positive) lead to the striped end of the diode. You should measure around 60VDC. It may be as low as 40V but not lower. It should not be higher than 70V.

If the voltage is higher than 75V, check the wall-power supply. You may need to use one that is lower voltage and/or current rating. Do not continue if the voltage is higher than 75VDC.

Unplug the DC jack and continue to measure the voltage on the diode. It will slowly drift down. When it is around 15VDC you can continue to work on the kit.
The next step requires placingC5. This capacitor is 100V so make sure to use the the one with kinked leads!

Place the last 0.1uF/100V capacitor C5 which works withC7 to smooth out the boost converter

Next the PLCC socket. Like the microcontroller socket, this protects and holds a chip. This chip is for driving the VFD display. Unlike the other socket, this one must go in the right way.

If you do not put the socket in right, it will be very difficult to fix so make absolutely sure you do not get this wrong!

In the bottom left corner you will see there is a flattened edge in the silkscreen.

When you place the socket, make sure you place it so that the corner that is flattened goes in the bottom left.

Check this more than once so that you do not make a mistake, as we said it is very hard to fix this if you get it wrong.

Once you are sure you have done it right, flip the board over and solder in all the pins of the socket and the capacitor.

Then you can push the MAX6921 into its socket, it will only fit one way due to the notch in the chip

Before the next step, check out your ZVP2110A MOSFET (Older versions of the kit may have a ZVP3306). There's two possible shapes. One shape has the text on the flat side of the FET. The other shape has the text on the round side.

The photo on the left shows it on the curved side.

If you're used to transistors with the text on the flat side, this can be a little confusing!

Use care when working with the MOSFET. They are easily damaged by static discharge. Work with all parts on an anti-static surface and ground yourself to it before handling the device.

Next place 22 ohm resistor R3, this is the bias resistor for the VFD tube heater. The resistor is symmetric.

Also place P-channel MOSFET transistor Q4 (Q3 on earlier kits) which allows the microcontroller to switch off the display when in low power mode.

The transistor must be placed correctly: make sure the rounded half of the transistor case matches the rounded silkscreen.

Solder and clip the components.

Next place the 2x10 0.1" spacing female header. it goes with the socket facing up.

Hold the socket in place, while you solder in two opposite corners, to tack it place.

Then hold it up and look to make sure that the socket is sitting flat against the PCB before continuing.

Finally solder in the rest of the pins.


Now we will solder the headers on the matching part. Place the smaller PCB in the vise and make sure the silkscreened part is facing up as shown. The kit will not work if this part is flipped.

Place the right angle 2x10 male header as shown

Tack the header from the top to keep it in place. Then do the same test as you did with the female header and make sure that it is sitting as flat as possible.

Once you have verified the header is straight, solder the rest of the pins.


Clip the pins. Be careful and wear eye protection. The little pieces can fly off and hit you if you are not careful!

Now gently unwrap the tube, and clean the wires if they are covered in wax with warm water and a paper towel/napkin.

Look at the wires near the front. Right in frontmost you might see 3 wires that are not connected to anything. Please click the photos to the left to see larger detailed images. If you do not see 3 disconnected wires (19 pin tube, not 22, go to the next step).

Separate these three wires out.

You may have a tube that does not have 3 not-connected wires. in this case, the spacing will be different in front and you'll see two wires that seem 'farther' than the others. They are right in the front of the tube and are the two pins in the 'middle' of the front plate (which has 4 connections). Make sure you have identified the correct wires, please click the photos to the left to see larger detailed images as its much easier to see than explain.
Madworm suggests cutting the wires in an angle so as to make it easier to place them into the PCB, so you may want to try it!

If you have non-connect wires, thread these three wires as shown so that they pass through the holes marked "Display NC" (not connected).

Alternately, if your tube does not have non-connect wires, thread the two front wires so that they straddle the NC pins but do not use them.

Please click the photos to the left to see larger detailed images.


Now pass the remaining wires through so they pass straight through and are not crossed or bent.

All the wires should have a hole that lines up except the three non-connect wires (if they exist).

Straighten out the wires with pliers and slide the tube down. This will take care and patience as the wires are thin and bend easily. Work slowly and use pliers to gently pull on any kinked wires.

Make sure you have the tube positioned correctly since it will be nearly impossible to fix if the tube is not aligned correctly or soldered wrong.

Push the tube so that it is a few mm away from the PCB.

Before soldering, do a test by plugging the tube into the mainboard. Tubes vary a lot and some are bent a little. Make sure that tube is straight with respect to the main PCB. You can pull the tube a little to angle it so that it ends up straight.

If you want a perfect fit, assemble part of the enclosure now and verify that the tube will fit nicely in the box with the tip flush with the enclosure side.

Once you are satisfied, bend the wires out to keep the tube in place and solder each wire, making sure to have no shorts.

Clip the wires when done.

Once you are satisfied, bend the wires out to keep the tube in place and solder each wire, making sure to have no shorts.

Clip the wires when done.

Don't forget to install the MAX6921 before continuing

Clear off your desk and plug in the DC adapter. You should hear a beep and the display turn on and display some numbers (probably 12 00 00) If you get anything on the display you're doing great and the tube is working well. Note that it will be very dim! That is because the display is designed to be at the lowest brightness (voltage) when first built. Once its in an enclosure you can make it brighter! If the tube seems to not be working, turn off all the lights and look again.

If you're having problems, check that you have the boost converter working, that you installed all the parts including the chip and that all pins are soldered well. With the MAX6921 chip in place, the boost converter voltage will no longer be outputting 70V but will measure at around 20V, this is OK.

If you need to probe the voltage, remember not to touch the right hand side of the board. Use a nonconductive vise to hold the left side near the 5V regulator only!

Once you're done, unplug the DC jack and wait a few minutes to let the boost converter drain.

Remove the tube from the mainboard.

We will now assemble the backup coin battery circuitry.

First, melt a tiny bit of solder onto the center tab of the battery holder. This will make good contact with the battery.

Now place the 12mm coin battery holder.

Solder the two tabs, they dont stick out all the way past the PCB, so you'll have to hold it in place with tape or a finger.

Solder in the final Schottkey diode (D4), this one keeps the battery disconnected until the main power dies. Place it so that the stripe is on the left hand side. Solder and clip the diode.

Now we'll place the buttons and switches. The alarm on/off switch SW1 goes on the left near the PLCC socket. The three buttons are identical and go in locations S1, S2 and S3.

Flip the board over and solder in the switch, you may need to hold it in place with a finger.

The buttons should snap in place but make sure they are sitting flat against the PCB before soldering them in place

Finally, if you're planning to ever ugrade the firmware or hack the clock, solder in the ICSP header. The longer pins go on top.
You're done! Now its time to make the enclosure. Do not operate the clock without an enclosure! An insulating enclosure is essential to protect the user from accidentally touching the high voltage on the VFD display.

This guide was first published on Mar 06, 2013. It was last updated on Mar 06, 2013.

This page (Board Assembly) was last updated on Feb 28, 2013.

Text editor powered by tinymce.