It's time to review one of the most popular Nixie kits around. The Spectrum from PV Electronics is one of the standards of Nixie Kit builders since it was launched. It supports large tubes, and in this review we're using IN-18 tubes, which are still quite easily available, but which are starting to reach quite high prices. Expect to pay around $50 per tube for them, so that means a clock with IN-18 tubes will set you back around $400 before you have a case. I paid around £85 for the kit, so that's a bit over $100 dollars at the current exchange rate. Cases are available, but I didn't get one. I probably still will, but that's a thing for another day.
I have never looked at the Spectrum 18 before getting the kit to review it. I was aware that it is large format tube clock, the PCB measures 280mm x 80mm, but had not looked at the circuitry in detail. The package arrived quickly, but slightly damaged. Fortunately, the contents of the package was not affected by the damage to the packaging.
The PCB appears to be of high quality, with gold-plated pads and matt back solder mask. Before starting, I did a quick check I found several problems. Contacted Pete and told him about this, and he immediately replaced the PCB free of charge, and no questions asked. That's service!
The build manual is excellent, with plenty of clear illustrations and explanations. It is clearly laid out and takes you step by step through the build. I intend to more or less blindly follow the manual for this build. Scanning what there is to be done, it does not seem a challenging kit at all. All the tricky parts seem to have been dealt with (for example, the high voltage power supply comes already assembled). Things like pull up resistors for the back light LEDs are supplied as 9-pin SIL resistor network arrays, so also they are easy to install.
With this review, I'll also take you through a couple of "gotchas" that you should avoid doing. I'm building it so that you can learn from my mistakes.
Talking to Pete about the design decisions he made assures me that this is a clock intended for a long life. First of all, the tubes are already long-life doped tubes, secondly, the IN-18 tube seems to appreciate being used in a "direct-drive" clock. This means that the tubes are not rapidly multiplexed (switched on and off), and instead each digit element is supplied with a constant voltage, but at a lower current. Multiplexed clocks, although simpler, drive one tube at a time, and to achieve the brightness, each tube must be supplied with more instantaneous current. The average current remains the same, but the dreaded blue dot can appear in cases where the drive current is not exactly right.
Also the fact that tubes are socketed shows that this is a maintainable, high quality clock. One word of warning here though: Even if the tubes are socketed, refrain as much as possible from plugging and unplugging the tubes: the tubes are fragile, and the strain put on the pins during insertion and removal can cause out-gassing, which means the end of the tube. You should unplug and replug tubes only for valid reasons, such as replacing a damaged tube for good.
The High Voltage generator board is a separate board for the simple reason that if any part of the electronics needs replacing, it will be this part. The high voltage generator circuit gets hot and each time there is heat, the life of an electronic component is reduced. The rest of the circuitry is not under strain at all, and can be expected to last indefinitely. Having said this, even the HV board almost never fails, but if it does, it is a 2 minute job to change it.
The tube holders are acrylic mounting boards which diffuse the light of the RGB LED underneath the tube and also serve to hold the pins in place. Taking the covering off the acrylic can be a bit tricky, but rubbing the foil hard with a thumb can cause it to release easily. There is only one thing you have to be careful about with the tube holders, and that is to make sure you insert the pins from the right side and with the pin jaws pushed into the acrylic first.
Some of the holes are too big to take the pins, and this is intended. Not all of the pins on the IN-18 need to be used, and the larger holes are to remind you that the pin does not need to go in that hole.
Next you have to put the resistor networks onto the board. Make sure you do this from the bottom side of the board! If you do it from the top side of the board, the resistor network packages foul the tube holders and it gives an ugly result. In general, look for the silk screen marking that should guide you which side to mount components from. In this case, the silk screen rectangle is on the bottom side of the board.
The long SIL (Single In Line) packages for the resistor networks are not polarised, so you can put them in either way round.
Next you can put the tube holders onto the board. These should be mounted from the other side to the resistor networks, so, from the top of the board. The "notch" in the acrylic holder has to go near where the RGB LEDs pins go,
The low voltage power supply is a run of the mill buck regulator circuit using an LM2576. This has the advantage that it does not dissipate a lot of energy, and therefore increases the efficiency of the clock. The circuit is extremely straightforward and is taken almost directly from the data sheet:
The only modification is that the input and output smoothing capacitors have slightly different values, and the Schottky diode is a generic 1N5819 instead of the 1N5822.
The capacitors and the regulator are laid down to reduce the profile of the board. You have to be careful to mount the capacitors with the correct polarity: make sure that the white stripe on the capacitor matches the markings on the board.
The inductance and the socket are mounted on the bottom of the board.
Testing the low voltage circuit is easy. Power on the board, by connecting the power and check that nothing gets hot. After a few seconds if nothing gets hot, you can test the voltage at the test points on the top of the board. The test points are conveniently located on the top of the board, and are clearly marked.
The high voltage supply is usually the hardest part of a clock to build, but PV Electronics has taken a good route for the Spectrum: Instead of having individual components on the board to make the high voltage generator, the high voltage is generated by a pre-built and tested module. From one point of view, I think this is a clever move. If any part of the clock is going to wear out, it is going to be the high voltage generator: it gets hot and does a tough task, and for sure doing it this way means that there are less support calls. On the other hand I feel that part of the fun has been taken away. I'm sure it is not the general feeling that people will have.
The high voltage generation is therefore much easier to build than on a traditional clock. It only takes a few minutes, and if I understand the circuit correctly, the controller only needs to be installed to turn the generator on via he module's "enable" line.
The tube drive circuit is made up of two HV5622 specialised controller ICs, which are purpose designed for driving high voltage circuits. The are 32 bit shift registers, with 32 output drivers capable of easily driving Nixies. They are quite easy to control, and in total there are 64 outputs. These are arranged as 6 x 10 outputs (for the tube cathodes) plus 2 x 2 further high voltage drivers for the separator neons.
The HV5622 appears to be running out of specification: The data sheet says that the supply voltage should be 10.8V - 13.2V, of course meaning that 12V is the ideal voltage, but in the Spectrum, it is being run at 5V. This rather neatly gets around a interfacing problem with the logic levels that the PIC controller can supply. If you had the HV5622 running from 12V, normally the defined logic levels should be that LOW is less than 2V, and HIGH is greater than 10V (which is vcc - 2V). Running the 5622 out of spec, makes the login interfacing easy, but it is outppf spec. I suppose here that he PIC can't drive the 5622 at anything near the 8MHz data rate, and this makes the combination reliable at 5V.
The only other point to note is that the sockets for the PLCC packages have to be put in the right way round, with the notch on the socket matching the notch marked on the silk screen. Get this wrong and you will suffer a lot.
The PIC controller has a great feature that Atmel controllers don't: they have an on-board Real Time Clock circuit (RTC) which only needs an external 32.768kHz crystal to make it work. The controller processor clock is then derived from this using a PLL. This part of the circuit is really easy.
While I like the idea of having the IN-18 tubes socketed (there is really no alternative), I'm not a huge fan of the sockets on the Spectrum 18. I had to fiddle about with them for a long time, and to my (rather conservative) tastes, they grip the pins on the tubes a bit too well. I know that a good connection is important, but these fragile old tubes don't like to be forced to do anything. They might not fail right away, but I always get the feeling that it is so easy to damage the tubes in the process of forcing them into the sockets.
I do see the need to have the acrylic holders, so that the pins don't get out of alignment, but I get the feeling that they constrict the pins a bit, meaning that excessive force might be necessary. I have no proof for this assertion, it's just a feeling I get.
These two sections of the manual deal with filling in some of the discrete components that are used in the clock. R8 - R11 are ballast resistors used on the neon indicators. R12 - R14 are current limiting resistors for the LED indicators, R17 - R19 are used for the speaker. R16 is a pull up resistor for the temperature sensor and R20 appears to be a total waste of time.
The drivers are the Q1, which is an MPSA42, which drives the speaker. This is a high voltage transistor, but I suppose it was chosen because it can withstand the voltages used in Nixie tubes, and the MPSA42 is being used here as a jelly-bean NPN transistor. Q2 - Q4 are used to drive the three channels of the RGB backlights.
C5 and C6 are a super capacitor and a decoupling capacitor, as well as a header to allow the board to be quickly reset. This circuit allows the clock to keep running which the power is turned off for a limited period of time. This means that the clock does not immediately forget the time.
This section of the manual deals with installing the LEDs (D4 to indicate if the alarm is active, D5 to indicate if GPS module is active, D6 to indicate that Daylight Savings Time is on), the switches and the connectors the for external PIR and GPS/DCF module). I decided to install the LEDs standing upright, because I didn't want them protruding over the edge of the board, btu then found out that the switches protrude anyway. Depending on the sort of case you install, you might need to install some of these components on the botton of the board, so read the manual carefully!
Well, that didn't take long! The buzzer is installed on the bottom of the board. I can't really find anything else to say about it.
Up until now, the clock has seemed to be a really well-designed and thought out kit, but this step feels a bit "how you doing" in comparison. The installation of the RGB LEDs is fiddly, hard to get right, and unnecessarily troublesome. The bending of the leads is a bit approximate, and you need to pay good attention to the orientation of the LED when you start bending the leads. In my kit, I had a spare RGB LED, and I suppose that this is because lots of people get at least one wrong. If you don't pay good attention to the way up you hold the LED when you start bending, it comes out with the common lead in the wrong position. Take good care!
Soldering the LEDs is also a bit awkward. The leads to be trimmed are difficult to trim, even wth tiny side cutters.
In the end, soldering the LEDs happened without any great mishaps, but I would have hoped for a better solution than what was offered.
Well, that didn't take long.
This is a fiddly task, and while going through it, I found that the manual is wrong. It says to cut the heat shrink sleeving for the neons with the long legs to 45mm, but that is too long for the glass tubes that are supplied. Instead I cut them to 40mm and that turned out just perfect. I also shrank the heat shrink sleeving before the final soldering, so that the heat of the soldering would not cause the extensions to drop off.
After installing the separators, I gave the clock a quick test. My tubes have cathode poisoning, and I'll show you in a later article how to deal with that, and also give the clock a full user review.
I'm totally satisfied with the resulting clock. The Spectrum 18 kit is easy to build, and works well. The instructions are clear where they need to be, and short enough when there is no need for additional explanation. There are no complicated components to deal with, and as an overall impression, the kit is well worth the money. It has a good set of features, and is well thought through.
There are a few parts of the construction that don't match the overall quality of the rest of the kit. The tube holders don't fill me with confidence, and I feel that they are a bit brutal with the delicate and expensive IN-18 tubes. The mounting of the RGB LEDs feels a bit improvised, and a jig or on board LEDs might be a great addition to the kit. The leg extensions on the neons is a bit fiddly, and seems also a bit improvised.
However, these are minor niggles, and on the whole, the kit is excellent! I would recommend it to anyone wanting a large tube clock.
This is the data sheet for the Microchip HV5622 high voltage (Nixie) driver chip
Recently on the Facebook Nixie Clocks Fan Page, Peter asked if anyone had a design for a Z1000 tube mounting board. I did something for a friend who had a box of Z1000 tubes, and didn't have the possibility to design boards himself.
Here is the KiCad archive (design files and Gerbers, in the "CAM" directory):
ZM1000 6 digit display board, without separators
In the post today a new piece of equipment arrived from a friend of mine in the Netherlands, who spends far too much time in electronic junk yards, fishing for equipment to make things out of. He recently found an original Philips PM2422A multimeter with ZM1000 tubes. He was kind enough to send it to me. This is the opening of the package and the testing to make sure that it had arrived safely.
The meter uses 3 ZM1000 tubes, a "half digit" tube, capable of displaying a "1", and another small tube, capable of displaying a "-". I have no idea what the "half tubes" are. Here is a picture of the ZM1000 tubes in their original location:
The "half tubes" can be seen to the right of the three ZM1000s: there is a tall thin one, which shows the "1", and a round one (with the yellow wire) which is the "-".
There is also plenty of dust in there as well.
Here's the video of the unboxing:
One thing that manufacturers of today should take notice of, is that equipment of the era the PM2422A was made in always had a service manual available for them. This one has a chunky 62 page manual that explains everything about the way the unit works, as well as detailed instructions how to maintain and trouble shoot the unit. Try finding a piece of equipment with that level of detail today!
If you want to have a look at the manual, it is here: https://www.tubeclockdb.com/downloads/Philips_PM2422A_ENG.pdf
This clock was kindly supplied by Millclock for review, so many thanks to them for sending the clock to me. Previously we reviewed one of the simpler clocks produced by Millclock (the IN-12 Walnut clock) and this time we're looking at the other end of the range.
The Nixie Six is a six digit IN-14 clock with compact digits and a whole load of features. The version I have comes in a formed black acrylic case, with a sturdy transparent base plate, neon separators, and an external 12V power supply. The appearance is pleasing:
The power supply has a slightly smaller than usual jack, but is a standard DC jack, and has quite a short lead, but I'm sure that you can find a supply with a longer lead if you need it. For most purposes, the lead supplied will be adequate.
The unit has GPS time synchronisation, meaning that it keeps good time. The GPS antenna unit has a very long lead on it, meaning that you can easily and unobtrusively mount the antenna in the vicinity of a window, which is a pre-requisite for good time synchronisation.
Whereas the IN-12 clock gave the impression of being a pre-production unit, the Nixie Six is very definitely a mature production design. There are no rough corners or loose ends, and everything fits properly and clearly a lot of time has gone into making it a polished unit. Indeed, the clock version number, printed on the bottom of the PCB is v2.0.1, again with the slightly strangely motto "properly assembled in UKRAINE". I do understand why Millclock is trying to say with this motto, and I do know that I am being somewhat facetious, but in English it just sounds a bit strange. I wonder what the difference in assembly would be if it was "improperly assembled". Would that mean that it is assembled by children? Or by slaves? Or perhaps by adults, but with their trousers down? Or all three? I know that Millclock are trying to say "assembled in the UKRAINE with care and attention, using state of the art technology and tools, great quality control and an eye for detail", but somehow "PROPERLY ASSEMBLED IN UKRAINE" has a better right to it,
The pitch of the tubes is quite tight, with only about 1mm between adjacent tubes in the digit pairs. This gives the clock a very "upright" appearance, especially because of the relatively large base height. The mixture of the black acrylic and transparent acrylic base work well. One slight improvement that I would suggest to Millclock: It would be good to have some rubber feet on the bottom of the acrylic base: acrylic scratches easily and the beautiful finish will deteriorate quickly if it is left as a raw acrylic on any hard, rough surface.
The clock arrived very quickly and was well packed,with no damage to the unit at all, and with very little risk of being damaged, even given the fragile nature of the IN-14 tubes and the fairly large size of the assembled clock. The box it came in was a sturdy "Ukraine Post" official box, and priority postage was used. Note that the cost of the postage is in the price.
The first thing to say about the Nixie Six is that it works well, keeps time reliably, and is in no way "needy". I have been using it for a couple of months, and it has never put a foot wrong. It's totally silent in operation, and has been a "fit and forget" experience. The GPS unit means that it tells the right time and you won't need to fiddle or adjust the clock at all. Even changes to Daylight Savings Time (DST) are automatic if you are in Europe or the US, or in a country that follows either of these DST change standards.
The GPS time is backed up by a battery powered Real Time Clock (RTC), and so the clock can run even there is currently not any GPS signal available. As with all GPS devices, it can take a couple of minutes to sync the time the first time, because the inbuilt GPS receiver has to understand where it is, and which of the GPS satellites are in the sky above it.
If you don't have the GPS version, there is the possibility to fine adjust the RTC unit, in units of about 5 seconds per day. RTCs are usually very accurate, but even these can drift over time or under certain circumstances, and the adjust feature allows you to correct this.
The manual is much longer and more detailed than with the very simple IN-12 4 digit clock, covering five A4 pages, and the specifications and the usage of the clock are covered. The main "settings" are laid out in an easy to use table, and the clock has three buttons ("menu", "+" and "-"):
A feature that I do like, is that the neon colons flash can be set to one of seven different modes:
1 - slow flash: One second on, one second off
2 - fast flash: 0.5 second on, 0.5 second off
3 - fast burst flash: two rapid flashes at the beginning of each second
4 - medium burst flash: two medium flashes at the beginning of each second
5 - "ping pong right": both separators on, but the brightness switches between the left and right separator (right colon mostly bright)
6 - "ping pong left": both separators on, but the brightness switches between the left and right separator (left colon mostly bright)
7 - "ping pong alternate": As "ping pong" but the bias changes each second (alternating between left and right bias).
This clock won't give you "feature overload", the ones the clock offers will cover the vast majority of user wishes, and you won't have to get exasperated by wading through the manual to fine what you want. It is mostly very intuitive.
Millclock didn't know that I was going to tear the clock down, but I think it is worth having a look inside it to see what you are getting. In general, if you are scared to have your clock torn down, then don't send it in!
The case comes apart quite easily and non-destructively, meaning that it will be a fairly simple task to change the RTC battery if you need to in the future. The clock itself is a two board design, one board housing the driver, and the other board holding the tubes, the separators and the RGB back lights.
The internals are really clean and professional. The board is well laid out, logically divided and neat and tidy. The tubes are all perfectly aligned, and have been clearly inserted using a jig, or by someone with a good level of skill.
The clock uses an STM32F103C8 controller, which is a powerful ARM Cortex-M3 device with 64kB of flash and a maximum clock speed of 72MHz, but in the case of this clock, it is using it with a 32.768kHz external crystal for the inbuilt RTC and probably uses the internal RC oscillator running at 8MHz for the control circuitry. The RTC consumes just 1.5uA when the clock is off, so a standard CR1220 battery with a capacity of 36mAh will last about 24000 hours, or about 1000 days. However, the 32.768kHz crystal is not temperate compensated, and therefore the need for the RTC calibration. I would complain about this if the clock did not have the GPS antenna, but it does have GPS, and is unlikely to give you any problems in practical use.
The display is multiplexed using a K155ID1, and uses classic NPN-PNP discrete drivers for the anodes, using SOT-23 transistors marked 1D (NPN) and 2D (PNP), presumably the MMBTA92 which has a voltage rating of 300V, or the KST93.
The tubes are mounted close to the display board, with just enough clearance under them to allow the SMD 5050 RGB LEDs to be mounted. The RGB LEDs, which are divided into three sets of two RGB LEDs, one for each pair of digits, using NPN transistors marked 1GW, which is a general purpose SOT-23 NPN transistor.
Millclock are following a strategy which I think is the right for them to build a brand over the long term: Offer high quality items at the price which allows you to guarantee the quality. Millclock clocks are not cheap, but if you want to have a no-nonsense, "get-it-done" clock, you will not be disappointed if you buy Millclock.
Buyers of luxury items (and let's face it, Nixie clocks are luxury items: a $3 LED or LCD clock will tell the time just as well) forgive the price if the quality is there, but will not forgive failure and unreliability. From this point of view, I think Millclock are on the right path, and the Nixie Six is good choice.
Millclock offer a one year warranty, and will give you a 10% discount if you mention this article!