Casio PT-80,
Casio MT-18		 small keyboard with nice analogue rhythm & accompaniment

Casio PT-80

This keyboard has many similarities with the Casio VL-Tone 1 and PT-1, but includes a "melody guide" key lighting feature for music teaching (not the keys itself light up but a row of small LEDs above them) and a ROM- Pack music cartridge slot. Unfortunately this instrument is missing the great built-in synthesizer, sequencer and 3 octave switch of the VL-Tone.  Like the Casio PT-30, the single finger chord concept of this instrument makes chords selectable by name instead of pressing multiple keys, but unlike the latter it is even more restricted and permits only 4 different chords. Besides the white version, this instrument was also made in red. The original German retail price in a German Conrad catalogue from 1986 was 299DM (about 150€).
 
(This is an eBay picture; my PT-80 is missing the cartridge lid.)

main features:

The PCB has empty solder holes, but unlike Casio PT-30 these ones have no printed component names.

modifications:

notes:

The speaker has an unpleasant, loud mid- range resonance. The hardware of this instrument consists of 2 large, stacked PCBs with much analogue stuff. The upper PCB has empty soldering holes for a 16 pin DIL IC, those unlike the rest are not labelled with component numbers. Very interesting is that this instrument contains the same CPU (D1868G) like the (older?) Casio PT-30, but the latter has additionally the small IC "HD B 61914" (44 pins SMD) that communicates with it. First I thought the small IC would be an external program ROM, but I guess that the different 3 following digits of the CPU type number indicate a different internal ROM software.

The monophonic main voice sounds much like a Casio VL-Tone 1; unfortunately it lacks the famous "fantasy" sound of the latter. Much like with the VL-Tone 1, the harpsichord sound suffers from a too slow attack rate, which makes it unrealistic.

Although the single finger chord section looks interesting, its capability is very restricted; during rhythm the organ chord is always replaced by automatic accompaniment (like with most keyboards) and it is also generally impossible to play fewer or different tones than a standard 3 or 4 note chord, and unlike the PT-30, this instrument even plays only 4 different chord types and nothing else. With rhythm, once the accompaniment has started (by touching a chord key button), you can not stop the accompaniment again (i.e. pause chords) without stopping also the rhythm.

Rhythms are selected by OBS buttons, and by pressing the button of the already playing rhythm, a fill-in is inserted. The analogue rhythms resemble the Casio PT-30, but additionally they have an unusual popping base drum, that sounds like an exploding firecracker far away. The percussion has an interesting timbre with partly long sustaining white noise "cymbals". The toms seem to be based on squarewave tones produced by the main CPU and muffled by external capacitors.

The instrument was sold with the Casio ROM- Pack RO-551"World Songs", which contains the 4 songs {1= "Unterlanders Heimweh", 2="Greensleeves", 3="Die Lorelei", 4="Old Folks At Home"} and has a "not for sale" notice. All these  musics have a great and complex orchestrated arrangement. The ROM- Pack cartridge employs the same conductive carbonized silicone rubber connector that is used in many LCD watch displays. More interesting is that the musics from it can be used with "melody guide" training feature, in which a flashing LED (next key) and a lit LED (current key) in the LED chain above the keys teach monophonic keyboard play. It has 2 training levels {1= keeps playing, 2= waits for correct key}. With the "cancel guide" button the LED row can be switched off, thus the same 4 variants like on the later Casio PT-82 exist. But the PT-80 does neither include the great "rating" feature of the latter. When the instrument is switched on, it plays a tone scale (8 notes) while a light runs from left to right on the LED chain.

A likely direct successor of the PT-80 was the technically simplified Casio PT-82 (which unfortunately misses the chord buttons and has boring blip drums).

Casio MT-18

(photo taken from eBay, showing my specimen)

This brown keyboard is simply the midsize version of Casio PT-80. Thus the main voice is still monophonic despite bigger keys. The specimen I bought even came with the same ROM-Pack RO-551.

different main features:

notes:

Very unusual is that the MT-18 contains a different CPU despite the behaviour is identical with the PT-80. Thus I guess that the same CPU core was only re- released in a different package or manufacturing process for technical reasons, while the internal circuit stayed the same. Also the PCB layout and material looks very different. Despite it worked well, I found in my Casio MT-18 an exploded electrolytic capacitor (which I replaced).
 
 removal of these screws voids warranty...    
WarrantyVoid
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