LEGOBLASTER! - LEGO Ghettoblaster
LEGOBLASTER: a 6600-brick LEGO model of a 1980s ghettoblaster with radio,
cassette, CD player, motorised/functional components, and detailed internals.
LEGOBLASTER - This 1980s style ghettoblaster uses 6631 bricks and includes an AM/FM radio with working tuning knob & waveband pointer, a motorised front tray-loading CD player, a motorised cassette recorder with working soft-eject, 4 speakers, 2 microphones, a graphic equaliser with LED bargraphs, front and rear connections, battery compartment, aerial, and a carry-handle.
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LEGOBLASTER - This 1980s style ghettoblaster uses 6631 bricks and includes an AM/FM radio with working tuning knob & waveband pointer, a motorised front tray-loading CD player, a motorised cassette recorder with working soft-eject, 4 speakers, 2 microphones, a graphic equaliser with LED bargraphs, front and rear connections, battery compartment, aerial, and a carry-handle.1
The front of the unit contains the controls, all of which can be operated. These include; vertical linear sliders, vertical two-position slide switches, rotary knobs (one of which moves the radio tuning pointer), and spring-loaded pushbuttons (one of which operates the cassette ejection system).2
The top of the unit has a carry-handle that can be folded down, and an aerial that can be extended and positioned in 2 axes. The side of the unit includes finger grips so the unit can be lifted easily when the aerial is in the extended position and the carry-handle in the folded down position (you can't change the position of the carry-handle whilst the aerial is extended). The side also has vents, and there's additional vents on the rear too.3
On the front of the unit next to the main speakers there are two internal microphones, connectors for external microphone & headphones, and a 3-digit tape counter with spring-loaded pushbutton reset (the digits don't rotate or anything, to do so would have made it too bulky).4
The CD player includes a motorised front tray-loading system, motorised head positioning, and motorised spinning of the CD. There's also six spring-loaded front-panel pushbuttons representing the functions; play, stop, pause, next track, previous track, and eject.5
The cassette recorder includes motorised gearing to the drive spindles for playback, fast-forward, rewind, and even raises the heads and pinch-roller up to the cassette on playback. There's also six spring-loaded front-panel pushbuttons representing the functions; record, play, stop, rewind, fast-forward, and eject - which actually opens the front-loading cassette drawer using a soft-eject system controlled by a damped shock absorber.6
The cassette is inserted to the front drawer and guided down between some slopes to initially rest on two tiles at the bottom of the drawer. Pushing the drawer closed causes the cassette guides (two grey curved slopes sticking out from the back wall) to raise the cassette slightly allowing the capstan and drive spindles to stay properly aligned with the holes in the cassette as the drawer closes.7
The rear of the unit contains additional vents, a battery compartment with hinged cover, the extendable aerial, the fold-down carry-handle, and rear connections for audio and power. I had intended to remove the central section of the rear case that sticks out but it turns out there wasn't enough room - the CD tray when inserted is hard up against the inside of the rear case, and there wasn't even room to move the batteries forward either.8
The carry-handle folds down partially into the recess in the top of the case. It contains Technic Axle rods for strength, although I'd still recommend lifting carefully with two hands. The aerial is built from two of the longest Technic Axles covered with Technic Ribbed Hose and contains a series of Hinge Arms that allow it to unfold in the middle, elevate, and rotate. It folds because I couldn't see a good way to do a telescopic aerial on this scale.9
The rear connection panel includes stereo phonos for Line-In and Line-Out, along with an external power socket. The batteries in the battery compartment are loosely inserted and held in place by a hinged cover with two blue thumbscrews that rotate behind the outer case to hold the cover in the closed position.10
Rear cover removed showing the internals, including a long circuit board that continues behind the battery compartment and has the rear connector panel mounted onto it. The carry-handle supports extend all the way down into the base of the unit for maximum strength so that when you lift it by the handle you are actually lifting it from the base.11
Side view of the CD mechanism, cassette mechanism, and battery compartment. It's pretty tight for space in there! I built the cassette mechanism first so I'd know how much space I had for the CD mechanism, but there's more than a few places in there where I struggled to get it all to fit, especially with 6 motors, 39 gears, 17 springs, and other moving parts.12
The cassette is only very slightly larger than the real thing. Every connection is completely legitimate but the strength is a little on the weak side with only a single stud holding some sections together. A stronger more detailed version is possible, but it becomes too large and would affect the size of the cassette deck. The transparent window uses 1x1 plates & tiles, the latter of which seem to be pretty rare (listed on Peeron as single supplier at $4 per tile). Time to get some superglue...13
Cassette soft-eject mechanism: the cassette drawer is pivoted and contains a lever arm to the rear. Pressing the spring-loaded front-panel eject button moves a series of rods that push the spring-loaded black slope back thus allowing the damped shock absorber to expand pushing the lever arm up to softly open the drawer. Pushing the drawer closed causes the lever arm to push the black slope back until it springs back out above the arm locking the drawer in the closed position.14
Cassette drive mechanism: blue motor driven clockwise drives gear A fast anticlockwise, gear B fast clockwise, and gear C slow anticlockwise. Green motor/gears slides the grey drive-plate D left/right to select red gear E or F to drive a cassette spindle. Thus PLAY is C-F, FAST-FORWARD is B-F, and REWIND is A-E. Cassette spindles rotate freely in the STOP position where no gears engage. During PLAY, the drive-plate slope also lifts the head/roller assembly up to the cassette, spring-loaded to return down when PLAY deselected.15
The CD mechanism from the rear, with the tray closed (left) and opened (right). The mechanism features motorised tray-loading, raising of the CD off the tray, raising of the CD head, motorised disc spinning, and motorised head tracking movement. The next image explains this in more detail.16
Insert a CD to the open tray. The red motor/gears drive the tray into the unit via a long rack mounted on the underside wall of the tray. When it gets to the rear two push plates under the tray push the orange pivots which lift the purple head balancing plate & drive spindle, which tilts the optical head up and raises the CD off the tray sandwiching it between two rubber wheels. The blue motor/gears then rotate the drive spindle and thus the CD. The green motor/gears can then move the head in and out for tracking purposes.17
The AM/FM radio features a functional tuning knob that when turned drives a Technic Chain Link mechanism that moves the waveband pointer left and right until it hits the end-stops. If you're under the age of 25 you may not have seen this before but that's roughly how analogue radio tuners used to work, albeit the chain link was usually one or more rubber belts & pulleys that if you dismantled you had practically no chance of putting back together again!18
The big bad bass loudspeakers. They're pretty big - just two of these and a single cd/cassette deck with minimal surround have taken the width of the overall unit to over 64cm, which is pretty big for a ghettoblaster.19
The equaliser sliders are implemented with a forward-facing tile sliding up and down a fixed rearward-facing tile. The sliding part then has a shock absorber brick with the spring pushing the slider into the front of the unit so that the movement is stiffened and the slider doesn't fall out of position due to gravity. The rear cover is removed on the lower image so you can see the shock absorber assemblies.20
Front and rear of the LED bargraphs, complete with its own driver circuitry. I haven't really decided if the 10 equaliser sliders are 10 filter channels or 5 stereo filter channels each for left and right, but in either case the LED bargraph had to have 11 columns because "LEGOBLASTER" has 11 letters :-)21
The battery compartment houses 6 D-cells. They are not attached, they just sit in the holder and are held in place by closing the outer case cover just like on a real ghettoblaster. However, the stud on the tip of the battery does mean you need to slide a whole row of three in together at the same time.22
Available in black too! (shopped)23
CAD screenshot showing the full model.24
CAD screenshot showing cassette mechanism partial internals.25
Description

This is an LDraw virtual LEGO model of a 1980s style ghettoblaster with radio, cassette recorder, CD player, and graphic equaliser.

The model features a number of working parts including an ejectable cassette and CD, and a working radio tuning pointer. It also attempts to simulate some of the internals by motorising the cassette and CD player functions. Being a virtual model it's difficult to know for certain if these functions would all work on a real model, which is why I normally don't build technical models like this, but I'm confident everything should work possibly after a little tweaking. The most questionable part is the manner in which the CD spun, which I'd probably do differently if ever doing this again. I could have gone for the easier top-loading CD player, but I really wanted to have a motorised tray :)

Further descriptions appear under each image as you browse through the available images.

Everything was built with MLCad, using LDView for previews and exporting to POV-Ray for ray-traced renders, with the assistance of some PHP scripting. All parts used are standard LEGO parts/colours attached in the correct fashion, albeit possibly in a colour that part was never produced in.
Model Features

Radio • AM/FM tuner
• functional tuning knob and waveband pointer
• extendable 2-axis positionable aerial
Cassette • front-loading drawer with functional soft-eject system
• motorised tape spindle drive (for play, fast forward, and rewind)
• spring-loaded front-panel buttons (one operates the eject system)
• 3-digit tape counter with spring-loaded reset button
CD • motorised front-loading tray mechanism
• motorised disc spinning
• motorised head tracking
• spring-loaded front-panel buttons
Equaliser • graphic equaliser with slider controls
• LED bargraph display
Miscellaneous • stereo loudspeakers (2 bass, 2 tweeter)
• inbuilt stereo microphones
• front connections for headphones & microphone
• rear connections for line-in, line-out & power
• internal circuitry
• rear battery compartment
• two-tone grey/black case with yellow/blue trim and foldable carry-handle
• all controls are functional: either rotary, slide, or spring-loaded push-button
Model Stats

Size - Metric - mm643 x 177 x 372
Size - Studs81 x 23 x 47
(size with handle/aerial down)
Total Parts6,631
 Bricks1,618
 Plates2,571
 Tiles1,054
 Panels58
 Slopes361
 Wedges120
 Arches48
 Technic Parts636
 Hinge Parts127
 Other Parts36
 Technic Motors6
 Technic Gears47
 Technic Axles98
 Technic Bushes71
 Technic Pins72
 Springs/Shocks33
Software Used

Building & Rendering
MLCad v3.40 • LDView v4.01 • PHP v5 • POV-Ray v3.6
Image Processing
Paint Shop Pro v7.04 • IrfanView v4.27 • PNGOUT v1
LDraw files for this model are not available for download
First Published: November 2012. Last Updated: November 2012. My LEGO Stuff
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