Tea Table - furniture that runs MAME

1987

Manchester University.

The student's union.

Fresher's week - beer - pizza.

In a dark and slightly pungent corner of the Solem bar, far from the scrum, two upright cabinets, one instantly forgettable, the other 'R-Type'. This game was a favorite of mine I can safely blame much of the last year's spare time on that game, but first a little personal history.

I grew up with computers, and we're talking about computers that you Had To Make Yourself. I remember the adverts that used to litter the back pages of Hobby Electronics and Electronics Today International, showing great praire-like motherboads stuffed with 14 pin DIL chips. Among these, the Microtan 65 and MK14 Sinclair offerings were just what a geeky 10 year-old wanted. Exactly, why I wanted them, and what I would do with them, I had no clear idea. Somehow the very idea of owning your own thinking machine was reason enough, as if it somehow made the future come one step closer, and then of course we would one day own a real laser (wowee!) and surely flying cars and weekend trips to the moon were just around the corner.

The reality was more prosaic but still intoxicating. Holidays in Scarborough or Sheringham rekindled the idea that somehow the magical games (Space War, Pong) in the arcades were related to the slabs of fibreglass forested with quad CMOS NAND gates that I could buy for 'only' 100 quid or so. I'm not alone in having first met computers through gaming, but at the time owning a computer was a non-trivial step until Sir Clive's ZX81.

"Time passes. A dwarf appears and throws a Z80 at you."

Anyway. Here we are. A quarter of a century later, and I and my wife are the proud owners of a MAME-based piece of furniture. Its name, 'Tea table', reflects the fact that it can actually do useful service as an occasional table, albeit one that lights up, makes noises, and has a higher SPEC-mark than the glowing Appley thing that I'm writing this on.

Rather than break down the construction into separate pages, I've put all the images and text into this one page. Most of the general details about building MAME-cabinets are covered well in 'Project Arcade' by John St. Clair , a useful book to read, and a fund of information about suppliers and so on. Where this project has departed from the usual run-of-the-mill is in its general layout (a table-like critter) and in its use of a TFT screen.


And so it begins...

Well, on with the show. After much thinking and faffing, my wife and I decided to build a home-friendly gaming machine. This would be a PC and would run MAME, allowing us to relive those happy days of yore as well as play back CDs and DVDs in an easily manoeuvred cabinet. The design we opted for means that it can be turned into a piece of furniture when it is not being used as a gaming machine. A quick look-see with a CAD package gave us some ideas, such as those below. The tricky thing being that we didn't want something that looked like an anonymous wooden cube, and the only way to support the screen in that case required the use of legs in some manner.

Preliminary hokey ideas.

We settled on a plan, which is summarized in the next cartoon.

Tea table had its main components built out of plywood, and I opted for two different thicknesses, using 12 and 16mm board as need arose. The joinery is pretty basic; I went for a screw-and-glue approach using 40mm countersunk woodscrews. You don't need to see a great photo of some sheets of plywood, so here's a noisy low-res image.

Tea table comes in two parts, the lower box which contains the computer, and the upperbox which houses the screen. Both of these boxes have the same square 500mm x 500mm cross-section and are of differing depths - obviously, the PC-holding box is deeper than that for the screen. Here's a GIF of the cutting plan, to be used as a guide only.

Now, before you buy any lumber and start cutting it, I strongly recommend that you make some cardboard mock-ups of your provisional design. Not only will it give you a good idea about button positions and so on, but it will allow you to see and feel how different sizes and shapes work for the various parts of the unit.

Once you've got a design that works, and that means, you've measured all the bits that go into the case (PSU, drives, motherboard, sound devices, etc) then set to and with screwdriver and wood-glue, put the bits together.


The Main Box

The lower box houses the motherboard and cards, drives, keyboard processing board, and audio gear. All major cutting work is best done right now before mounting any hardware and much of the woodwork revolves around getting air through the box, sound out of it, and control lines in. Well, Tea Table isn't a terribly powerful beast, but we do want it to work without straining itself. The power supply (a 450W model by Sweex, dual fan and very quiet!) was uncased, and I've tried to optimize the air flow around those components that need it most. Air exits the lower box through a single blown hole at the rear, and enters the box through two side-panels. Two rectangular holes in the lower box were cut, with recessed borders to allow pieces of aluminium mesh to be sunk and epoxied into place.

Other holes are cut for the power socket (a standard IEC connector) and switch, the main fan, the front socket panel and the speaker grilles. These last were also recessed as I wanted to have the front panel as 'clean' as possible.

I chose a low-power motherboard and CPU, deliberately. Our design means that ventilation is somewhat less than you might have in an upright cabinet and so I found a micro-ATX board from Asrock (K7S41) with an AMD 2800 mobile processor. We've given it 512 Mb of DDRAM, which clocks along at 333 MHz. This motherboard and the accompanying DVD drive (LG, single layer) and hard drive (40 Gb IDE, Western Digital) is powered from a fairly standard ATX PSU. Note, for both the motherboard and PSU I've chosen to mount the PCBs on sheets of thick polycarbonate plastic. This looks a little nicer and means that I can handle the boards a little more easily, without worrying about shocks or ESD.

Each of these plastic sheets is mounted to the plywood by protruding studding that has been epoxied into the wood. In case I needed to replace an item, I didn't want to be fiddling underneath the lower box with a screwdriver to undo a fastener. This means that every item mounted to the woodwork has had a hole sunk into it, into which a heavily epoxied set screw is fixed. As below.

On the inside, all wooden pieces are painted with flat grey primer.

The bottom box, which holds the motherboard and PSU, and the top-box which holds the screen, all were then sprayed with nickel screening spray to act as an RFI screen. Over this RFI screen I've put a clear layer of varnish, and an electrical connection is made between the main power supply earth terminal, the RFI screening of the bottom-box, and the lid. This connection is achieved by a scrap of copper plate and an old hacksaw blade; essentially acting as a spring-loaded connection between the lid and bottom-box.

You can see the leaf-spring in this full view of the lower box. In this shot you can also see the brown/blue wires that carry power to the top-box, emerging from a Cunning Hole in the right-hand leg. The power supply for the screen is in the upper-left corner of the image, just to the left of the fan for the PSU board.

My wife and I spent a fair bit of time wrestling with the conceptual skeleton of Tea table, trying to work out exactly how the screen would hinge and whether a rotating screen was desirable or feasible. In the end we went for a fixed screen in a traditional 4:3 landscape aspect. Oh, this blather all naturally assumes that you've taken the plunge and bought a flat screen monitor with the sole goal of gutting it for the display unit.

:|

We decided to put a CD-ROM drive in there so that we install drivers and whatnot more easily. It's an LG DVD ROM (DRD-8160B) so we could even use Tea Table as a DVD playback device if the mood were to take us. Now, if I'm running a Molex lead and an IDE cable to the CDROM, it makes sense to also have the hard disk somewhere nearby so that the cables can be bundled somewhat. So a pair of aluminium brackets were made that ensure that the drives stand apart from each other and also have a good size gap under them to improve air flow.

You'll see that for the above test we had a stock keyboard and mouse, and those are the last thing that we want for driving a MAME box. You want joysticks. And buttons. Lots of buttons. The best way to get an idea of where you want your controls is to go to an arcade, blow some cash and *play* various games with different arrangements; spot what you like and make a note of it. Once you've an idea of what works for your handsize and preferred game type, then lash together a mock-up using a cardboard box and some button/stick types. I opted for microswitches rather than leafsprings (the debates are legion) and bought a pair of Happ 360 optical sticks and also a pair of 8-way microswitch sticks for comparison.

However, these don't just plug into a USB or serial port. I bought the rather fine I-PAC/4 from Ultimarc, and this board plugs into a serial socket and allows a gloriously large number of switches to be interrogated. I opted to recess the speaker grilles as well, but to leave the control panel exposed proudly in all its multi-socketed glory. This is a picture taken half-way through the installation process, with epoxy and abrasive paper still being used to flatten the fit.

The D-shell connectors that you can see are for the control boxes, these sockets are bolted to an aluminium plate that fixes to the front face of the lower box. This plate also carries the volume control knob and a USB socket for handy connections to keyboards and mice. Since Tea table has a fairly hefty audio output, I thought that it might be nice to have a 3.5mm headphone socket on the front panel too, for headphones and such like. Although with the racket from the buttons on the control box, I doubt that quiet gaming is possible.


Control boxes

The boxes are made from the same brand of plywood used for the main boxes, but opting for thinner pieces to reduce the weight of the boxes. Each box is designed so that the upper surface will slope at a gentle angle, as you can see in this image.

Each box has a pair of side holes for buttons, and carries four aluminium tapped pillars in the corners, to accept the fasteners that hold on the top-plate. Each pillar is epoxied in place with high-strength epoxy (none of this 'rapid' stuff please - there's a trade-off between strength and speed of cure).

With the top plate off, you can see how tight these particular dimensions were - the joystick shaft protruded just enough for me to have to scoop out a depression in the control box's base so that the stick's motion wouldn't be impeded. Note also a few epoxied-in studs to hold the terminal blocks for the cabling.

Right. The top-plate. I opted for sheet aluminium for that, and took a little while chain-drilling holes to get the desired layout. You can use plywood if you like (makes for a chunkier box), or plastic, but I favoured toughened aluminium 1.5mm plate (nope, no idea of the grade).

Then, the surface was scoured with abrasive paper, and brought to a uniform sheen with metal wadding polish and a few minutes with an orbital sander converted into a cotton-rag polisher. The finished result is rather nice.

With luck you'll find a sensible way of drilling the holes in each corner of the top-plate corner so that they line up with the mounting pillars. I didn't. Counter-sunk holes in the top-plate mean that hands won't catch on fasteners when gaming. In the next image the top-plate has been drilled for its support columns and had its corners radiused.

Each box has 1 stick, 2 side buttons, and 5 (five!) forward buttons, I need some way of keeping the spaghetti to a minimum. Terminal block is your friend, recall that I had those posts epoxied into the base of each box? Well, this is what they look like when populated.

And here's one of the control boxes completed; opened.

And shut.

For connecting the control boxes to the main unit, I opted to use shielded multi-core cable. I dithered for a week or so if some kind of radio link wouldn't be a better idea, and toyed with building my own serial encoder, and feeding the output of that into the transmitter of a little RxTx transceiver. But sense got the better of me. For starters, a wire link is a darned sight easier to debug, and although less robust, I had to wonder how much grief Tea Table and its connectors would see. The control boxes I've built have seven pushbuttons and a single joystick. In total, that makes one common rail and eleven signal lines. Shielded cable is a little chunkier than unshielded, but any reduction in RFI is worth half a mm of diameter. As for the connectors, each control box cable ends in a high density 'D' shell plug. These are generally seen as VGA connectors on computer monitors and they give 15 pins in the footprint of a standard-pitch 9-pin 'D' shell connector.


Painting

Tea Table has a black and silver theme. I used multiple coats of thinned high gloss oil paint on the control boxes, main box and screen box, applied with a foam roller. I learned (fast!) that I should use many thin coats, each one ideally sanded down lightly to provide a key for the next layer. The fun didn't stop there though. To achieve a high gloss and repairable surface I then gently abraded and then spray-painted the oil paint with multiple coats of aerosol (alkyd carrier) gloss black. This was then polished with a polishing compound called Commandant - a bit like T-Cut, but it doesn't use a petroleum-derived solvent. The resulting finish would make Hotblack Desiato proud, and it's a good way of getting rid of holey underwear (really, cotton makes for a lovely rag cloth).


The Screen

Take heart, you're going to spend fewer Euro/dollars per screen mm^2 than we did. We can justify it because we're both silly. We chose a 19 inch screen from Novatech of Southampton and had no problems with dead or stuck pixels. It isn't a great screen, and I suspect it's a 6bit colour depth but we'll be playing pretty ropey games on it so that's not a problem. It has a single analogue input and is powered from a 19V DC PSU. The first thing to do is (of course) rag open the monitor's case and remove the panel. Naturally, you'll want the screen controls to be get-at-able, and so extract whatever push-button PCBs you find as well. We wanted the screen controls to be get-at-able and so we made up a remote board for the screen controls.

Of course, the sentence 'we made up' covers the messy reality of the Tea table project. Be thankful I didn't take pictures of the oh-so-fun times I had when recessing the air inlets or the speaker grilles.

For the true otaku-jin, you can get very wrapped up in screen contrast and refresh speed specifications. However, trial sessions with the monitor on my wife's PC showed a very acceptable image and the choice of a cheap/cheerful monitor was vindicated. I also sourced a very low current 12 V fan, as I know that TFTs can generate a non-trivial amount of heat and so there is a second grill cutout on the rear face of the top box to accommodate the fan grille and the fan itself. I run this (at all of 4mA!) from the 19V provided to the screen via a dropping resistor.

Now, this lovely TFT screen has to be protected from abuse by something. I've chosen a large sheet of tinted plastic as a screen protector. There are two grades of acrylic; cast and extruded. Cast is a little more expensive than extruded, but has better optical properties and is no different in handling and cutting. I bought my screen plastic from Basmaplast of Weesp and got excellent serivce at a very good price. The piece I picked is 570 x 570 x 8 mm, in a 20% tint, and is shown here just as it came out of the cutting area.

I chose a tinted acrylic for a couple of reasons. Firstly, no matter how much I sweat over the TFT panel, it's still going to be visibly different from the rest of the innards of the top-box. So darkening the viewing screen will at least mute the sight of the guts of the top-box. Secondly, it looks cool. Note, it looks darker in this photo as the flash has to go through the sheet, be scattered from the paper, and then pass back through the sheet. In use, with the TFT panel providing the light, it won't look quite so dark.

To prevent bodily injury and so on, I've radiused the corners - pretty easy to do as acrylic is fairly forgiving as a plastic.

The screen protector is fixed to the upper box of the Tea table by way of four pieces of aluminium angle-section. These are cut and filed so as to fit flush against the outer wall of the upper box as can be seen in this picture. Sanitary-grade transparent silicone mastic then joins the screen protector to these aluminium pieces.

Here's how it looks as the silicone is setting - be generous with the silicone, I learned the hard way that too little leads to voids.

Once set, I ran a sharp blade gently against the aluminiumn struts to slice the silicone, which was then rubbed away with that handy keratinous-edged blunt tool on your hand.

The aluminium pieces are bolted to the upper box by counter-sunk set-screws that fasten into captive nuts mounted on the inside of the top-box walls. All fasteners and so on were sourced from the good folk at Kruyt (ironmongers since 1890!) in Leiderdorp.

Of course, the box for the display has to not only hold the screen, but also should keep the electronics from rambling about in a dangerous manner. Once again, posts epoxied into the wood save the day, and as I want to minimize stray light, everything gets painted black.

Then, to obscure the screen surround, and the hinges for the top box, I made a bezel out of foamboard (two sheets of black cardboard, sandwiching a 3mm plastic foam layer) which is not only jolly stiff but also very low density. A good sharp knife, a straight edge, and some epoxy is all it takes to turn this...

into this...

I cut the foamboard into parts that I had determined from cardboard mockups, and then simply epoxied the parts together. Once set, the foamboard was painted with gloss black and then sprayed with a matt black aerosol paint - do paint hte foamboard first - the cardboard outer layers are very absorbant and you'll waste a lot of paint in trying to get a good finish. Then, after a little more jiggling and persuasion, the bezel can be fitted. I'm not attaching it firmly, as the screen plastic does an excellent job of gently holding it to the screen.

Apologies for the dust - and the flash makes it look scabbier than it really is!


Structure and Mechanisms

The whole point of this project is that not only can the object serve as a table, but it must be playable from a seated position - which means that the screen must be tiltable. So far you've seen the lower box which contains the computer itself and a little of the upper box which holds the screen. We now introduce the bits that join the two together. I chose to use stainless steel for the structure of the legs, and used a square section tube of around 20 x 20 mm and a wall thickness of 1.5 mm or so. Two lengths of this tubing were bent gently to give radius of curvatures of about 35 cm, with judicious use of heat (hint, two blowtorches - minimum, and go easy on the pushing and work it when yellow-red hot, you don't want to be heaving hard in case you slip).

These two uprights attach to a pair of legs that fix to the inner base of the lower box. The joint that links the upright to these inner legs is pretty important, the way in which the upper box hinges means that the uprights holding the upper box are offset somewhat, so the joint at the base of the uprights needs to be strong. I chose to have those parts welded by a local company. Of course, I first had to discover the hard way that the brazing material I was using didn't have enough strength - hey ho.

So, I went to the nice people at GOBA in Leiden, and they TIG welded the parts together. With a bit of jiggling and filing these fitted nicely, and with those secured I was able to mark out and fit the various strengthening brackets and plates that I also wanted to use. Firstly, there's the matter of making sure that the two legs have both ends (upper and lower) fixed in some way that they keep the same distance from each other (that they don't wobble independently) - then there's the matter that they can't wobble as a pair either. Below are the various means of preventing the above. Overkill perhaps, but I don't want a nasty accident.

So here's the leg, note the little triangular plate of 3mm steel.

And here's the strut for the top-box (the one holding the screen, stay with it!) which will allow the top-box to pivot.

Here's the stiffening plate that makes sure that the legs are locked together midway up their length - it's a thin sheet of stainless steel with a gentle curve for stiffness, brazed to two drilled end parts.

This plate bolts onto the legs which now have a pair of threaded studs tapped and brazed into them.

Then it's merely (ha!) a matter of offering up the legs and their struts to the woodwork, and attaching appropriate fasteners. The following images are brought to you after much pleading to the gods Nnnrg and Arrrg.


Miscellaneous

So, now it's all starting to come together, there's a PC, a screen, some way of holding the two together, but critical parts left to describe are the wiring harness and interfaces.

Clearly, the PC needs to talk to the screen. I had drilled and filed two generous holes in the top and bottom of one of the stainless steel legs, and so after cutting the video cable in two I was able to feed the cable up one of the legs from the bottom box to the top box. A little snipping, some soldering, a little heatshrink, a little home-made screening (aluminium foil soldered to a twisted chunk of the cable screen) and the screen is driven well.

So far the player/user can only communicate with the PC by the control boxes - not the best approach when you're trying to mouse to an icon or type some test. I therefore added an internal USB socket to the case, wiring it to the motherboard's USB pins. A little nosing about on the Web led to the purchase of a iOne RF keyboard with built-in pointer. The transmitter for this keyboard plugs into the internal USB socket and I've extended its antenna so that 40cm of wire is outside the rather nice Faraday cage that is the lower box - thanks to the RFI nickel screening that I laid on it many moons ago.

I laid the antenna wire horizontally along the seam where the lid meets the bottom box, and chiseled out a little trench for it. Some epoxy, some paint, and a quick rub down with abrasive paper and Commandant, makes for a nicely hidden antenna wire.

Currently, the hinges for the top-box are nice and tight, with no indications of loosening. However, when rolling Tea table around, it might be an idea to lock the screen box on some way to either the horizontal or its play orientation. To that end, I made a pair of locking lugs and brazed them to the legs - in the expectation of some day fitting slide-bolts to the underside of the top-box.


Hard at Play

And here's a little movie (Quicktime, about 3 Mb), the audio quality isn't great. In reality there's a heap of bass and the audio amplifier board puts out enough power for it to be uncomfortable to be close to Tea table for long at full volume.

Legal bit I do not advise the illegal use of ROMs without the copyholders consent. The above construction description is not designed to encourage copyright infringement, Tea table is a very happy DVD/CD playback machine and the provision of control boxes is to permit legal ROMs to be played with MAME. Naturally.


Sources for Parts

Tea table was built using parts from a wide variety of sources. Locally, I bought various bits and bobs from
W.P. Hartwijk & Zn BV, Nieuw Beestenmarkt 7-11, Leiden.

And from an excellent iron monger, Kruyt, Nieuwhuizenweg 19, Leiderdorp.

The joysticks came from Happ and the buttons for the control boxes came from Tornado Terry's arcade supplies.

The screen came from Novatech of Southampton, England. Numerous odds and sods, such as the caster wheels, came from Praxis at Leiderdorp, a generic DIY store.

Paint both gloss and primer, as well as the spray paints were from the local HEMA.

The screen plastic was from Basmaplast of Weesp, and they supply different opacities and thicknesses of acrylic.

2009 Upgrade!

Ah, the time has come to give Tea-Table a boost - specifically we now wish to be able to play those fine games Sudeki and Overlord. So now Tea-Table has an AMD 5050e processor, a 3/4 of a Tb SATA drive, 2Gb of RAM and a decent graphics card (ASUS Silent 512Mb 8400GS). Mind, I did add a teeny tiny fan to the pleasingly large heatsink of that card; 60 degrees is a mite too warm for my liking when just idling - and with a fan it stays under 50 when stressed even on a hot day.