Aiwa TPR-990
The TPR990 was introduced in 1980, and it was Aiwa's final and best "TPR" model. One year later, Aiwa abandoned the TPRs and replaced them with the "CS" model series.
The TPR990 has 16cm woofers and 5cm tweeters, and can be powered by 8 D-cell batteries. Its amplifier consists of a pair of Panasonic AN7146M chips wired in BTL configuration. According to Aiwa, its output power is 6 watts per channel (minimum), into 8 ohms between 60Hz and 10KHz. And maximum output is 10 watts per channel. This is more power than the TPR-950, TPR-955, or CS-770.
The dual-motor, soft-touch tape deck is very good quality, but difficult to service. Its Sendust tape head is capable of reproducing 45Hz to 18KHz (+/- 3dB) when using Metal tape.
The service manual for this boombox can be purchased HERE.