Casio PT-87


Casio PT-87

This grey cased instrument was a re- release of the PT-82 from 1987. (Inside the case embossed marks for 87 and {5, 6, 7, 8} make me conclude that it was manufactured between may and august in 1987.) Unlike the PT-82, it has the classical pale coloured Casio buttons again.
 
On this photo from eBayyou see my Casio PT-87 and my PT-82 (below).
The PCB of this specimen contains less discrete components, the shielding aluminium cardboard inlay is gone and the PT-87 has also no headphone jack anymore. The CPU is "HD61703B01, 7D 33". My specimen has a strange defect; when operated with batteries, it sounds distorted and howls, while with a power supply it sounds perfect. Apparently the battery voltage (5 batteries = 7.5V) is too low to operate the circuit properly - possibly a defective voltage regulator drops too much voltage.

modifications:

  • Power supply jack polarity changed and protection diode added (with PT-82 and PT-87).

Casio PT-20

(photo from eBay, showing my specimen)

This tiny instrument seems to be just a downsized Casio PT-30 and sounds very similar. (I haven't examined the hardware yet.) Unlike the latter it is missing the LCD, the cartridge slot, some of the sequencer buttons, the transpose buttons and 2 high note keys (thus also the "arp. 6" rhythm). Instead of separate rhythm and chord volume sliders it has only a combined slider. Its small case resembles the Casio PT-1. The original German retail price in a German Conrad catalogue from 1986 was 199DM (about 100€).

The likely most advanced member of this hardware family was the ultra- rare keyboard boombox Casio KX-101 (37 mini keys, chord button pad, complex sequencer that saves data on audio cassettes), which was even 4 note polyphonic.