Manual / Guide · 2016
87-page assembly manual for the no-IC KABtronics Nixie Transistor Clock (6 x IN-12A): parts list, build order, staged high-voltage bring-up, logic tutorial, circuit description, troubleshooting, and the 23-sheet schematic (Rev 5.0, 2013; scanned images, no text layer).
Nixie-Transistor Clock Assembly Manual K A B T R O N I C S I N T R O D U C T I O N Manual Version 1.2 1.3 1.4 Date 6/6/2011 1/10/2012 7/4/2013 PCB version Version 3 Version 4 Version 5 1.5 1.6 1.7 6/29/2014 4/2/2015 10/8/2016 Version 5 Version 5 Version 5 Change Details Initial shipments Updates from first builders PS drive circuit mod, 24 Hour shutoff mod, update schematic and BOM Add text for oscillator frequency selection Update BOM Add SENSE resistor selection text Document 1.7 for PCB version 5 Copyright © October 8, 2016 by KABtronics Nixie Transistor Clock Kit Page 2 K A B T R O N I C S I N T R O D U C T I O N Table of Contents INTRODUCTION........................................................................................................................................ 5 UNPACKING/PARTS LIST .......................................................................................................................... 6 SOLDERING .............................................................................................................................................. 7 UNSOLDERING ................................................................................................................................................. 8 OPTIONAL CLEAN-UP ........................................................................................................................................ 8 BUILD ORDER ........................................................................................................................................... 9 12 VOLT SUPPLY ............................................................................................................................................ 13 SECONDS COUNTER, DECODE, DRIVE ................................................................................................................. 22 THE REST OF THE COUNTERS ............................................................................................................................. 24 HOURS DECODE AND DRIVE ............................................................................................................................. 26 HIGH VOLTAGE POWER SUPPLY ........................................................................................................................ 29 HIGH VOLTAGE SWITCHER ............................................................................................................................... 30 NIXIE AND NEON DISPLAYS .............................................................................................................................. 34 FINAL ASSEMBLY AND TEST .............................................................................................................................. 36 PARTS IDENTIFICATION .......................................................................................................................... 38 RESISTORS .................................................................................................................................................... 38 CERAMIC CAPACITORS ..................................................................................................................................... 38 INDUCTORS ................................................................................................................................................... 39 DIODES ........................................................................................................................................................ 39 TRANSISTORS................................................................................................................................................. 40 TRANSISTORS – TO-220 POWER ....................................................................................................................... 40 LEDS ........................................................................................................................................................... 40 NEON BULB .................................................................................................................................................. 41 NIXIE TUBES AND SOCKETS ............................................................................................................................... 41 THEORY OF OPERATION ......................................................................................................................... 42 LOW LEVEL LOGIC ........................................................................................................................................... 43 COUNTER ..................................................................................................................................................... 44 CIRCUIT DESCRIPTION ............................................................................................................................ 47 IN CASE OF DIFFICULTY .......................................................................................................................... 54 GENERAL TROUBLESHOOTING ........................................................................................................................... 54 POWER SUPPLY DEBUGGING ............................................................................................................................ 55 DEBUGGING FLIP-FLOPS .................................................................................................................................. 56 DEBUGGING DECODERS ................................................................................................................................... 58 SPECIFICATIONS ..................................................................................................................................... 59 CIRCUIT BOARD VIEWS .......................................................................................................................... 60 SCHEMATIC ............................................................................................................................................ 63 COMPONENT SILK SCREEN SYMBOL ....................................................................................................... 86 Nixie Transistor Clock Kit Page 3 K A B T R O N I C S Nixie Transistor Clock Kit I N T R O D U C T I O N Page 4 K A B T R O N I C S I N T R O D U C T I O N Introduction Thanks for buying this kit. After about 20 hours of assembly, and with a clock to show for your efforts, I hope you will thank me for offering this kit. This is a complex kit meant for experienced electronic hobbyists. The High Voltage supply in this kit will produce over 160 Volts storing about 2 Joules of energy in the circuit. Touching the wrong thing, placing yourself in the electrical circuit will be very painful, and could possible kill you. You must keep your wits about you and maintain common sense protocols while working on this kit. I just have to make this obvious, so bear with me. This kit can KILL you if you come in contact with the 160 Volts. Here is the high voltage protocol – it applies after you build the High Voltage supply. • Build the HV supply last, after the rest of the circuit is done, tested, and working. • The 180 Volts will still be present even after removing power. o You must wait for the 180 Volts to bleed off after removing power. You can use a volt meter to check for a safe voltage. • If you are working on the board with the power applied, use the one-hand protocol o Use only one hand to move test leads and whatever else you are doing to the board, the other hand is in your pocket, this is to prevent you completing a circuit with your body. The worst you could do is short out one hand, very painfully I will add. Since you are an experienced kit builder the soldering section may be superfluous, you be the judge, but keep in mind; You need to make 2917 good solder joints to have the clock work. Also, a bad solder joint in the High Voltage supply can destroy components, perhaps in a spectacular fashion, if the voltage regulator isn’t working properly. Nixie Transistor Clock Kit Page 5 K A B T R O N I C S U N P A C K I N G / P A R T S L I S T Unpacking/Parts List Present X Nixie Transistor Clock Kit Qty 1 1 1 1 75 180 180 3 2 50 5 1 set 1 1 2 1 2 3 13 90 2 1 1 150 30 1 50 1 16 500 4 1 2 5 6 1 13 13 13 10 1 6 3 1 1 22 feet 6 feet Item Assembly Manual Resistor, 0.47ohm Resistor, 10 ohm Resistor, 100 ohm Resistor, 1K ohm Resistor, 10K ohm Resistor, 100K Resistor, 1Mohm Resistor, 22 ohm Resistor, 22K ohm Resistor, 220Kohm Resistors, 348K, 357K, 390Kohm Resistor, 47K ohm Capacitor, 120uF Capacitor, 6,800uF Capacitor, 10uF,16V Tantalum Capacitor, 0.001uF Ceramic Capacitor, 0.01uF, Ceramic Capacitor, 0.1uF, Ceramic Capacitor, 220pF, Ceramic Capacitor, 470, Ceramic Inductor, 220uH, Toroid Transformer, wall, 12VAC Transistor, NPN, 2N3904 Transistor, PNP, 2N3906 Transistor, NPN Power, TO-220 Transistor, STX13003G,400V 1A Transistor, PNP, MPSA56 LED, red 3mm Diode, Signal, 1N4148 Diode,1N5818 Diode,3A, 400V Zener, 4.7V, 0.5W Neon Lamp IN12A Nixie Display Heatsink, Dual TO-220 Nut, 4-40 Screw, 4-40, 0.5in Hardware, washer, 4-40 Nylon Tie Wraps TermBlock, 2 Pos Socket, Nixie, IN12A Switch, Fuse, 3A, Fast, pico PCB, Nixie Version 3 Hookup wire 2 conductor cable for power cord Page 6 K A B T R O N I C S S O L D E R I N G Soldering This manual can’t teach the art of soldering, but here are the basics. Remember, you need to make about 2917 GOOD solder joints; each bad joint will be an adventure in troubleshooting. Wet the tip of the iron with a bit of solder and wipe off the excess solder on the wet sponge occasionally, or when you notice the joint is not heating properly. The small amount of solder left on the tip helps conduct heat to the lead and the pad. Insert the component leads and press the component flat against the PC Board. Slightly spread the leads to hold it in place when you flip the board over to expose the back side with the component lead facing up. • Make good contact between the iron, the lead, and the pad on the board so the lead and the pad both heat up enough to melt the solder. • It should take from 0.5 to 1 second for the joint to become hot enough to melt the solder. • Don’t overheat the joint, as soon as the solder melts and wicks into the joint remove the iron and hold still for a few seconds until the joint freezes. • Be careful not to press too hard while soldering; the trace can break at the copper ring and that broken trace will be hard to find. Nixie Transistor Clock Kit Page 7 K A B T R O N I C S S O L D E R I N G A good solder joint will form a shiny curved surface bonding the lead and the pad on the PC board. If the lead wasn’t heated enough to melt the solder, the solder will wick in to the pad, but will not adhere to the lead. You may notice a dark line around the lead where the solder dives down through the hole. A similar bad joint forms when the pad wasn’t heated enough to melt the solder. A cold solder joint can often be fixed by reheating the joint; sometime a little more solder will be needed. More detailed instructions can be found on the internet with a little searching on the topic of soldering. After inspecting the solder joint, clip off the excess lead using the diagonal cutter. Cut at the top of the solder joint; don’t dig into the solder joint. Unsoldering A supply of de-soldering braid is supplied with the kit. If you find the need to remove a component, use the de-solder braid by pulling out a few inches and pressing the braid against the lead and the pad using the iron. You will see the solder melt and spread into the wick leaving very little solder left in the pad. Sometimes it helps to clip the lead off the component so you can deal with each lead separately. Optional Clean-up The clear sticky rosin left around the solder site can be cleaned up with alcohol (not “rubbing alcohol”) and a toothbrush, but be sure to let the board dry before expecting the board to operate properly. You won’t hurt the circuit by powering it up, but it won’t count right until the board has completely dried. As for me, I don’t bother to clean up the board unless the counters are not working right, then I do clean off the rosin. If you do clean the board, be sure to really clean it, not just redeposit the gunk over the board in an even layer; that will cause unreliable operation as these counters are very sensitive to leakage currents that will pass through the gunk layer. Nixie Transistor Clock Kit Page 8 K A B T R O N I C S B U I L D O R D E R Build Order OK, so here you are staring at about 1335 components with over 2900 solder joints to make. Please build it in the order shown in this diagram. Nixie Transistor Clock Kit Page 9 K A B T R O N I C S B U I L D O R D E R The list of clock sections and also the build order is; 1. 12 Volt supply 2. Prescaler 3. Seconds Counter 4. Seconds Decode and Drive 5. Tens Second Decode 6. Tens Decode and Drive 7. Minutes Counter 8. Minutes Decode and Drive 9. Tens Minutes Counter 10. Tens Minutes Decode and Drive 11. Hours Counter 12. AM/PM Counter 13. Hours Decode 14. Hours Drive 15. High Voltage Control 16. High Voltage Switcher 17. Nixie and Neon Displays There is a reason to build in this order; the NIXIE displays will not turn on until the 180 Volt switching power supply is built and working. The 180 Volt supply is the last item that should be built for safety reasons. So the question is; how do you test the time counters before the Nixies are displaying? The answer is to use LEDs at the right stage of building - when the decoders are half built. These LEDs replace the base junction and indicate when the decoder would turn on the transistor. These LEDs should not be soldered in, just pressed in the transistor holes. The short lead goes in the right hole in this view. Nixie Transistor Clock Kit Page 10 K A B T R O N I C S B U I L D O R D E R You will need the following tools to build your clock. • • • • • Soldering Iron meant for electrical work Small Diagonal Cutter Very small flat-blade screwdriver to tighten the wire terminals A multimeter to check for shorts and power supply operation An oscilloscope will be needed during the bring-up of the high voltage switching supply Silk Screen symbols Notice the silk screened symbols are only on one side, this side is called the “component” side, and this is the side where the components are placed. The side without the silk-screening is the “circuit” side. It is on the circuit side where the soldering of each component will take place. Most of the parts on the board can be located by the white silk screen symbol on the PC board. Here is an example of the power supply section of the board. Note how the component outlines have different line and blocks within the symbol outline. See how this power supply section within the marked area has four different values of resistors – the sharp cornered rectangles. NOTE: The symbols on the board trump, or override, any information in this manual, schematic, or BOM. Load the PCB according to the symbols on the printed circuit board. Nixie Transistor Clock Kit Page 11 K A B T R O N I C S Nixie Transistor Clock Kit B U I L D O R D E R Page 12 K A B T R O N I C S B U I L D O R D E R 12 Volt supply Let’s start. Locate the low voltage power supply section marked #1 on the diagram above. Check the PC board for a manufacturing defect that would short the power traces together. Use an ohm meter and check for an open circuit on the two pads for the 6800uF capacitor as marked above. If you find a short, check that there are no leads or pieces of metal on the front or back of the board, and that the table top you are using does not conduct. If your board shows a short, contact KABtronics for a replacement board swap-out. Here is a table of the parts you will load in the power supply section. This table only shows the parts in the power supply section Nixie Transistor Clock Kit Page 13 K A B T R O N I C S B U I L D QTY Item 11 100K resistor 4 10K resistor 2 1 Meg resistor 1 1K resistor 4 large diode 1 small diode 4 PNP transistor 5 NPN transistor 3 0.1 capacitor 1 0.001 capacitor 1 0.01 capacitor 1 6800 uF capacitor 1 terminal connector O R D E R Symbol Find these parts in the kit and prepare to load them. Here are step-by-step assemble instructions for the power supply section. The other sections will not be as detailed. Place the PC board on the table in front of you and identify the power supply section of the board. Nixie Transistor Clock Kit Page 14 K A B T R O N I C S B U I L D O R D E R Mount the 6800uF cap by inserting the leads in the proper pads, be sure to place the positive (+) lead in the square pad (nearest the board edge) and the minus (-) lead in the round pad. Before soldering, use a nylon tie wrap to hold the capacitor to the board as shown in the pictures. Solder and clip the leads close to the board, just above the solder meniscus. Also, clip off the nylon end piece. This is the last time clipping the leads will be mentioned, so you need to clip the leads without being reminded. Look at the terminal connector. You will see two small plastic “nubs” on the bottom of the connector that interfere with mounting this part. Use your diagonal clippers to remove these “nubs”. Mount the wire terminal to the board; be sure to face the wire openings to the outside of the board. Be sure the terminal is snugly against the PC board before soldering. You will have to hold it against the board while soldering, don’t get burned. Mount the four large diodes in the four locations below the large capacitor. Diodes have to be mounted to match the symbol; the white line on the part has to go the same way as the white line in the symbol on the silk screen symbol. Try not to overheat the part while soldering, this part is more sensitive to heat than resistors and capacitors are. Mount the 100K resistors matching the proper symbol. Mount the 10K resistors matching the proper symbol. Mount the 1K resistor matching the proper symbol. Mount the 1M resistors matching the proper symbol. Nixie Transistor Clock Kit Page 15 K A B T R O N I C S B U I L D O R D E R The small diodes may come packaged one of two ways. They may be loose in a bag, or they may be in a paper strip. If you have the strip, just clip the leads on both sides near the paper to remove the diode, don’t try to pull it out of the paper, you may damage the glass package. Mount the one small diode in this section. Be quick about soldering it, heat it just enough to get the solder to flow. The transistors also may come in one of two ways, loose or the paper strip. Once again clip the leads near the paper all at the same time to free the transistor from the paper. Mount the NPN transistors in the same direction as the symbol on the PC board. You will need to spread out the leads if you have the loose transistors, the paper transistors have the leads already formed. After inserting the transistor and locating it about ¼ inch form the board, spread out the two outer leads on the back side slightly to hold it in place while you solder it. Mount the 4 – PNP transistors in the same way as the NPN transistors. Mount the 2 – .001 capacitors, they should be snug against the PC board, spread out the legs slightly to hold them in place while you solder them. Mount the 3 – .1 capacitors exactly as the .001 capacitors. The power supply section is now done. Check for a short across the large capacitor using your ohm meter. You will see the charging of the cap with your leads in one direction, and you may see leakage current if your meter reverse polarizes the large capacitor. What you are looking to see is that you don’t have fewer than 10 ohms displayed continuously; you should see an initial low reading that climbs beyond hundreds of ohms. Next you need to wire the wall transformer. Follow the pictures on the next two pages. Nixie Transistor Clock Kit Page 16 K A B T R O N I C S B U I L D O R D E R Now wire up the PC Board. Here is a way to make a strain relief using a nylon tie. Nixie Transistor Clock Kit Page 17 K A B T R O N I C S B U I L D O R D E R Before you plug in the wall transformer, here is what might happen if you have made a mistake. If you: • Installed some of the large diodes backwards – you may be shorting out the wall transformer, which will overheat and be damaged and perhaps be a fire hazard. • Installed the large capacitor backwards – you may cause the capacitor to overheat, be damaged, and possible vent hot electrolyte liquid on you and other things which would rather not be vented upon. • Installed some smaller part wrong – you may find parts that overheat and possible smoke. Since you have extras, this is not the end of the world. Set your voltmeter to DC volts; prepare to check the voltage across the large capacitor remembering that the lead with the square pad, nearest the plus sign, nearest the outside of the board is the positive lead. Plug in the wall transformer and check for about 18 volts appearing on the capacitor. A few volts either way is OK. At this point, with very few components on the board, nothing should be getting warm. The voltage on this board at this point is low, so you can safely use your finger to test the temperature of the components (that will not be true after you build the High Voltage supply). Nothing should be getting hot. If one of the transistors or diodes is getting hot, you have made a mistake – you need to unplug, go back and double check your placement of the components. Nixie Transistor Clock Kit Page 18 K A B T R O N I C S B U I L D O R D E R If you have an oscilloscope, you could check to see if there is a 60Hz square wave appearing at the input of the prescaler. (Lower left resistor in the seconds counter, see flip-flop debugging) (Note: your switches are not loaded yet) Nixie Transistor Clock Kit Page 19 K A B T R O N I C S B U I L D O R D E R Prescaler Load the left half of section 2, the divide by 10 portion of the prescaler. There is not much to say here. I find it easiest to load about 10 components at a time before soldering. I load in this order; • • • • • • • Diodes 1Ks 10Ks 100Ks NPN transistors PNPs Capacitors Your board should look like this, Nixie Transistor Clock Kit Page 20 K A B T R O N I C S B U I L D O R D E R The right half of the prescaler has jumpers to choose 50 or 60 Hz mains. For 60Hz place a jumper wire in the three 60Hz locations. For 50Hz, jumper the two 50Hz jumpers. 60Hz 1 HZ signal going to seconds when completed 50Hz 50Hz 60Hz 60Hz Load the components and add the jumpers. Your board should look like this; Nixie Transistor Clock Kit Page 21 K A B T R O N I C S B U I L D O R D E R Seconds Counter, Decode, Drive Load the seconds counter, section #3 Notice that there is a pattern to each flip-flop. Load only the three 220pf caps for each flip-flop, shown above Do not the other 220pF caps scattered about the board with a dot in the outline. For example, don’t load these three caps. Nixie Transistor Clock Kit Page 22 K A B T R O N I C S B U I L D O R D E R Your board should look like the picture above. The low voltage power supply, the prescaler, and the seconds counter are done. Next, partially load the decoder as shown below, stop before loading the high voltage transistors. Insert the LEDs without soldering them. The short lead goes in the right hole. When you plug in the supply, one and only one LED should light up, and each second the next LED should light up. The pattern will go top to bottom and repeat. Nixie Transistor Clock Kit Page 23 K A B T R O N I C S B U I L D O R D E R The rest of the counters Load sections • #5 – Tens of Seconds • #7 – Minutes counter • #9 – Tens of Hours • #11 – Hours • #12 – AM/PM And then partially load • #6, #8, #10 decoders Now use the LEDs to test the counters. Use the time setting switches to advance the counters. Nixie Transistor Clock Kit Page 24 K A B T R O N I C S B U I L D O R D E R Now let’s discuss the other 220pF capacitors with the large white dot in the outline strewn about the board that are not part of the flip-flops. These are edge rate control capacitors and there are two for each flip-flop on the lines going to the decoders. They are not normally needed unless the edge reflections are causing issues with a flip flop. I have found, with a build sample of three clocks, that you should load the edge rate caps only for the hour counter and the AM/PM flipflop. That is a total of 10 - 220pF caps on the left of the board. If a counter is not counting correctly, first check all the components and solder joints. Watch and write down the count sequence. Think about what the sequence is telling you. It reveals which flip-flops are working, which are stuck, and which logic may be acting oddly. You can check if the input to a stuck flip-flop is changing, check the signal on the 1K input resistor (see the flopflop details on page 56). You can place the 220 edge caps without soldering for a troublesome flip-flop and see if that fixes the problem. Remember: you must have all counters, seconds to hours running properly before proceeding with the building of the high voltage supply. Nixie Transistor Clock Kit Page 25 K A B T R O N I C S B U I L D O R D E R Hours Decode and Drive You must decide between 24 hour or 12 hour operation. Load all of these For 12 hour operation, load these For 24 hour operation, load these Don’t load these yet. Load for 24 hour display Don’t load these yet, these turn off the display for each hour This is an always load diode, not a 12 hour diode. The circle is a trace VIA, look carefully Load for 12 hour display The 12 or 24 hour decode logic can be tested by placing the LEDs in the diode position for the “turn off at hour X” diodes along with a 1K resistor placed in the position shown in the pictures. Nixie Transistor Clock Kit Page 26 K A B T R O N I C S B U I L D O R D E R To test the grid logic, push the LEDs into the HV transistor locations with the short lead in the lower holes. The hole are labeled on the back 0-9 and T-0, T-1, T-2 so you can check if the decode logic is working. Nixie Transistor Clock Kit Page 27 K A B T R O N I C S B U I L D O R D E R This is a test of the 24 hour decode logic. Pressing the HR advance button causes the lit LED to walk down the rows. (you get 16 LEDs, so move them about) Below is a test of the hours decode for a 24 hour version showing hour 21 (21:00) Note that the 10K base drive resistors for the HV transistors are loaded in the picture below. Don’t continue until after you have all counters advancing properly. Use the Minutes and Hour advance switches to advance the counters while you watch the LEDs. You get 16 LEDs so you need to move them around as you test each counter. AM/PM display: There is a fifth Neon bulb display to the left of the Nixie Displays. You may want to load this only for the 12 hour version. The 24 hour version doesn’t need an AM/PM indicator, but you certainly can load it if you want. Nixie Transistor Clock Kit Page 28 K A B T R O N I C S B U I L D O R D E R High Voltage Power Supply Load the parts shown below; these build the oscillator and logic for the High Voltage supply. Load the OSC locations with 10K resistors. The silk screen symbols take precedence over the schematic, if you happen to notice any differences. Using an oscilloscope, check that the oscillator is running about 22 kHz and that the pulser is working. NOTE: the markings on your PCB tell you to load one 0.001uF and one 470pF cap. If your oscillator is not running near 22KHz, adjust the frequency by modifying the circuit. Replace the 470pF with a 0.001uF to slow it down, or replace the 0.001pf with a 470pF to speed it up. The spare 220pF caps can also be placed in parallel to with caps to slow it down. Pulser output shown. Nixie Transistor Clock Kit Horizontal 10uS/div Vertical: 5 Volts/div Page 29 K A B T R O N I C S B U I L D O R D E R High Voltage Switcher Load the power transistor (actually a Darlington) in the TO-220 package. Solder the three leads AFTER you have the heatsink, transistor, bolt, and nut in place and tightened to prevent stress on the leads. If you have some thermal grease, you can use a small amount, but it is not necessary. NOTE: your heatsink may look different (bigger). Nixie Transistor Clock Kit Page 30 K A B T R O N I C S B U I L D O R D E R Load the rest of the High Voltage power supply components BUT NOT; the FUSE, PWR resistor, or the SNS (Sense) resistor. Be sure to orient the long electrolytic properly, with the positive terminal connected to the + hole. Use the nylon tie to hold it in place. The inductor will need some creative lead shaping to fit the outline, you can do it. Your board should look like this; At this point, just loading the final three components and turning it on is too dangerous. If the logic section is not functioning, the power transistor could easily be destroyed when it shorts out the 12 volt supply. Another failure could be the voltage building up way beyond 180 volts and blowing up the electrolytic capacitor or the transistor. Here is the plan of action to safely “bring up” the HV supply. • Load the Sense resistor for a 25.5 volt setting. Put a 47K resistor in the SNS location. You will be removing it in a few steps, so you may want to not push it all the way down against the board. • Set inductor current limit to 70 milliAmps Load a 10 ohm resistor in the PWR location. • Protect the transistor in case of fault Load a 22 Ohm resistor in the FUSE location. • Test the general logic loop and the voltage limit logic Nixie Transistor Clock Kit Page 31 K A B T R O N I C S B U I L D O R D E R Connect your voltmeter to measure the capacitor voltage. See the meter leads in the following picture (the red and black grabber leads - not the scope leads.) Plug in the 12 volt transformer for just a fraction of a second. You only want it plugged in for less than a second. If all is working, you should see about 25.5 volts on the HV capacitor (not the 181.5 volts shown here) The 12 volt supply is actually putting out about 18 volts in this unloaded situation, but the point here is that the only way you will see a voltage above that level is with a functioning switcher circuit – so look for a voltage step up. If the switching is working, and the voltage limit is working, you should see the 25.5 volts. If you see over 30 volts, be glad you unplugged it quickly; be careful, don’t get a shock. Wait for it to drop before continuing. If you see about 25 volts, plug it back in and marvel at it. You have tested these items; • • • • Oscillator, & pulser Switcher Set-Reset logic Voltage regulator Current regulator Nixie Transistor Clock Kit Page 32 K A B T R O N I C S B U I L D O R D E R Don’t continue if you didn’t achieve the previous results. You need to go back and debug the problems before continuing, or you risk destroying components. Continuing the bring up steps; • Set the inductor current limit to 2.5 Amps, remove current protection Remove the 10 ohm in the PWR location and solder in the 0.47 ohm resistor. This will be the permanent component. Remove the 22 ohm and resistor and solder in the FUSE. Apply power again and once again you should see 25.5 volts. Use you oscilloscope to view the collector of the switcher transistor, see the picture above to see where to connect the scope lead to the free-wheeling diode. The second lead can be connected to the PWR resistor to view the transistor (and inductor) current. The scope shot below shows the current building to 2.5 amps, the transistor turning off, the collector swinging high to charge the capacitor, and the collector dropping when the inductor discharges (dis-currents?) Nixie Transistor Clock Kit Page 33 K A B T R O N I C S B U I L D O R D E R !!!After the next step, the voltage on the board will be very dangerous!!! 165 VOLTS CAN KILL • Set the voltage limit to 165 volts. Remove the 47K in the SNS location. Solder in the 357K resistor. Once again your fear should be that the voltage regulator will malfunction and generate greater than 180 volts. Test by quickly powering the unit while the voltmeter is measuring across the High Voltage capacitor. I just bump the 120 volt mains plugs into the mains until I am sure the regulation is firm. If you see about 160 volts, give or take 20 volts, and your voltage is stable - your High Voltage supply is working. You want close to 165 volts. The higher the voltage, the more power spent in the NIXIE displays, so, over 165 volts, your transformer may overheat. You are given three values for the SENSE resistor; 348K, 357K and 390K. A higher value raises the voltage. So if you have over 167 volts, try the 348K SENSE resistor. If you see under 160 volts, try the 390K. Whenever you have powered the board, you must wait for the 165 volts to decay below 20 volts before touching the board, and that can take minutes. Don’t get impatient and skip the voltage decay step, unless you like receiving painful and dangerous electrical shocks. Nixie and Neon Displays The NIXIE sockets present solder lugs for wiring. Do not solder these lugs to the PC board. These lugs need to remain free floating even after the wires are soldered to them. Nixie Transistor Clock Kit Page 34 K A B T R O N I C S B U I L D O R D E R . Next - load the forty five 22K NIXIE driver resistors (on the front of the board, like the other components, but you knew that). Each NIXIE location has a corresponding set of wiring holes. Each hole has a digit identifying the grid being controlled. Each NIXIE lug also has a grid number. There is also a COM lug to identify the 180 volt common lug that needs to be wired to the 180 volt hole near each COM lug. Wire the NIXIE in bundles as shown in the picture. Be careful not to nick the wire when you strip the end, you don’t want the wire to be weakened and break. Clip off the wire on the front to ensure it doesn’t bend and touch anything on the front. This is a picture of the lower three NIXIE wiring bundles. (Ignore the capacitor on the backside; this is a pre-production version of the board) Nixie Transistor Clock Kit Page 35 K A B T R O N I C S B U I L D O R D E R Final Assembly and Test Carefully push the NIXIE displays into the sockets. These displays are made of glass so be careful and don’t over stress the pins or you will crack the glass. Pin 1 is white inside the glass. Pin 1 is in the lower right position on the board. Plug in the clock and cycle thru the time settings to see all the digits display. You may want to check the voltage of the High Voltage supply now that the full load is present. It should not be too far below 180 volts. As long as your displays are all lighting up, you are fine. You have the option of loading some of the hour shut-off diodes if you want to turn off the display for some hours. There is one diode location with the diagonal line for each of the 24 hours. Loading a diode will turn off the high voltage supply for that hour. Nixie Transistor Clock Kit Page 36 K A B T R O N I C S B U I L D O R D E R You are done! Enjoy your clock, show it off to your friends, and be proud of your work. (And display this clock in a safe way, up high, behind glass, be safe!) Nixie Transistor Clock Kit Page 37 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Parts Identification Resistors Resistors can be identified by the color bands as shown in the adjacent chart (if this has been printed on a color printer). These parts can be placed in either direction on the board, they are not polarized. Ceramic Capacitors Ceramic capacitors are not polarized; place them either way on the board. You may receive these parts loose in bulk, or mounted on a section of tape. Nixie Transistor Clock Kit Page 38 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Electrolytic capacitors Electrolytic capacitors have the value printed on them. These are polarized parts; you must place them in the proper position on the board. There three of these on the board. Follow the instructions carefully when mounting this part. Inductors These are inductors. As a non-polar device, it can be loaded in either direction. Diodes The diodes come loose in a bag or on paper strips shown above. There are two sizes, small and large. The large diodes are used in the Power Supply section only. Diodes are polarized; the line on the component needs to match the line on the PC board symbol. Diodes can be damaged by overheating them during soldering, so be quick about it, but do heat the joint enough to make a good solder joint. Nixie Transistor Clock Kit Page 39 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Transistors Transistors come in two types NPN and PNP. There is a number on the package - 3904 is an NPN type and 3906 is a PNP type. You have a lot more NPN than PNP in this kit. Transistors come either loose in a bag or on paper strips. The paper strips are handy since after you clip out the transistor, the leads are space perfectly for mounting, with the loose transistors, you have to spread the leads. Transistors are also sensitive to overheating during soldering so be quick when soldering them. Transistors – TO-220 power This is a power transistor and it is used in the high voltage power supply. LEDs On the left is the single LED. It has a flat on the body and/or a short lead that marks the cathode, the negative lead. On the right is the 7 segment LED. There aren’t any of these in this kit. Nixie Transistor Clock Kit Page 40 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Neon Bulb These are Neon bulbs. They operate with about 70 volts and ½ milliamp. This part is non-polarized. Nixie Tubes and sockets These are Nixie tubes. There are 10 grids shaped 0 through 9 in a tube. The neon gas around the grid glows orange to indicate a number. These glass tubes are fragile, be careful when pressing them into the sockets. These are floating pin sockets, and that float allows for small position imperfections in the tubes. If the pins were soldered, excess stress could crack the glass. You will be using wires to connect to the sockets. Nixie Transistor Clock Kit Page 41 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Theory of Operation Below is the block diagram of the clock. This section will discuss the operation at a logic level; the next section dives down into the individual transistor level of operation. This clock is a chain of dividers, each divider clocking the next divider. For example, in the seconds block, the divide by 10 counter receives a once per second pulse and counts 0 to 9 repeatedly, producing a pulse at a rate of 1/10 second. Each of counters in the diagram above is a set of divide by 2 flip-flops and some steering logic. Nixie Transistor Clock Kit Page 42 K A B T R O N I C S P A R T S I D E N T I F I C A T I O N Low level logic A single flip-flop counts to two (0, 1). Two flipflops chained by connecting a Q output to the clock input of the next would count to four (0,1,2,3). Three flip-flops count to eight and four flip-flops count to 16. So how do we count to 10? The clocks must be controlled by logic gates as shown below. Two kinds of logic gates will be needed to drive these counter chains; And gates and Or gates. The And gate is high when both inputs are high and low otherwise. The Or gate is high when e