OT : The new Big Trak

This is off-tipic for 2 main reasons : (1) the device in question is not even 1 year old yet and (2) it's not a computer. But I suspect many people here rememebr the MB Big Trak programmable toy tank from the early 1980s, and may even rememebr the Circuit Cellar article that involved modifying one. So anyway... You can buy a modrn version of the Big Trak in the UK now. To the user it's much the same as the origianl version (I will mention differences) later. Inside it's very different. The cheapest I've found it in a shop is \pounds 34.00 in Hawkin's Bazaar. I've sene it for a few 10's of pence cheapr on the web, but then youy have to add shipping. Anyway, I am sure you know what I did to mine first, even before puttign the batteryies in and trying it out.Yes, I took it apart. Given that many people here are like me, I;ll explain how to do that. 1) Remove the battery cover (2 screws) and batteris if you have fitted them. 2) Next take off the plastic strips joining the front and rear axles. There are held on by 2 scres each (self-tapping screws with integral washers). If you have put the optional stickers on, you have to peel them off to get to these screws.. Then slide off the front and rear wheels. the centre 9driving) wheels are held on to the gearbox output shaftes hy a cetnre screw. Take these off next. 3) The next bit is non-obvious and had me puzzles for a minute or so. At he back of the lower body thre's a gey plastic part the only purpose of which is to hide a coupleof fixing screws. It's held in place by 4 plastic 'barbs', one each side and 2 along the rear endge. Carefully free it and slide it out downards. 4) Ondo the tiny screw thus revealed. Ths holds the kybaord bezel in plaec on top. Carefully unclip the bezel. On the underside of it is a little pCB carrying the power switch and the IR (?) LED for the trailer interfae. Undo the fixing screw, free the PCB amd set the bezel aside. 5) Back on the uinderside undo the dozen or so screws that hold the upper body in palce. Put the Big Trak the right way up and carfully lift off the upper bod. It's still linked by the flexiprint from the keybaord. This is not pluged in, it's clamped agianst the control PCB by a plastic clamp. Undo the 2 screws and lift of the clamp, then lift the kayboard tail over the pillers. The upper body is not free, 6) Undo the 2 screws holdign the LED holder for the 'photon cannon' in palce. This alos releases the loudspeaker which is lightly glued in place under it. Free that too. 7) I should have deoslderesd the battery wires next, otherwise you hve the lower body hanging on them, which is a bit of a pain. But I didn't. Anyway, undo th 4 screws on the bottom of the gearbox. Remove the gearbox complete with the control PCB downwards. The front axle is now free, don't loose it. 8) It appears that the PCB can be removed by desoldering the motor connectios (ML+, ML-, MR+. MR-) and then taking out the 4 corner screws. I have not done this. 9) The gearbox is held together by 5 screws on top (and can be dismantled with the PCB in palce). Take these out, turn the gearbox over, andlift off the cover. You can now see all the gearing. When reasbmbling note that there are several sies of selt-tapping screwn. Don't get them in the wrong holes... OK, diffeernces from the origianl version It runs everyting (logic and motors) off a single 4.5V supply (3 D cells in series) ratehr than +/-3V (4 D cells) and 9V (pp3) of the original version The 'photon cannon' is now an LED (blue I susepct) not a filament lamp The interface to the trailer is another LED (IR?) not a jack socket. The cotnroller bvoard is totrally redesigned. There are 2 ICs. These are epxoy-capped chip-on-board devices iwth a difference. They are not on the main PCB, they are on little daugherboards which are then soldered to the main PCB. The only think on the daughterboard is the epoxy-capped chip. So in theory they can be replaced. The larger IC is clearly a microcontroller (but not the TMS1000 of the origjnal one) in a package which looks to have the smae footprintas a PLCC device, I am not sure what the smaller IC is yet. Also on the PCB are a fair number of transsitors, R's and Cs, etc. Mostly SMD devices. The gearbox is redeisgned too. It's a lot easier to take apart and reassmeble than the orignal one. The magnetic clutch between the 2 motors is still there. The optical feedback from the gearbox is still there too. In fact there are now 2 IR light bariers, one for each motor, senmsing slots in the next-to-last gear in the train. I beelive the origianl version only had one light barrier. For a fairly cheap toy it's well made. It can be taken apart and put together again withut damage. Most of it is held together by self-tapping screws, but the battery cover (which the average owner has to remvoe and rrfit serveral times( is held on by machien screws going into tapped inserts in the lower body. Nice!. I may well do a Circuit Cellar style modification to mine (that is, a serial interfce thart simulates keypresses. Or maybe repaec the microcontroller totally. -tony