model 10 transistor radio
Made in Japan in 1972 for the Dutch market, the language on dial is Dutch, it is a cheap radio with electronic qualities of more expensive ones - bands LW, MW - Cabinet Plastic with leatherette, 25x16x7 cm - I bought it from Gerard Tel - Originaly 10 Transistors, now only 8 left after modification of the output stage - the radio is in excelent condition now and plays very well with output power of 1,5 Watts - the speaker is of good quality, it can handle 1,5 W and is made by Pioneer - Power 6 V, by 4 AA batterys (modification)
The LF power stage was defect, it is a normal 2 transformer push-pull output stage, but with 4 Sanyo 2SB77 transistors: 2 by 2 parallel. This parallel use of the 2SB77 caused instability and damaged the transistors. Only one thermistor should detect the heat in the transistors and then limit current through the transistors, no separate emitter resistors were employed that could stabilize the temperature effect of the transistors as is used in more expensive designs. The protection effect of it all appeared to be insufficient. Heat sinking seemed not to be a realistic option due to space limitations.
The stage was repaired already several times: some 2SB77s were replaced by 2SB54s. Modification was a consideration, after a few experiments the 4 transistors were replaced by 2 Sony 2SB383. The LF stage is very powerfull now, with very good sound quality.
Normaly it is not my habit to change the electronic design of a radio, but in rare cases like this, modification is in my view the only way to extend the life of a radio. Originally the power of 6 V was supplied by 4 'C' cells, and there must have been a AC-adapter. The battery holder was oxidated and damaged. It was replaced by a holder of 4 AA cells. On the pcb I found a modification with one 470 uF capacitor and a LF choke, for AC operation. Not having any function, the choke was removed, the capacitor stayed on the pcb for DC voltage stabilization purposes. After the repair the Tokyo has become a very good radio, one of my favorites, I like listening to it daily. PE1MMK.
As you can see here radio manufacturer ROSS made a radio similar to the Tokyo, by using the same cabinet. Just the dial is in another language: English and so the dial is slightly different. Also ROSS chose a different colour knobs, transparant in stead of black. This Ross lacks the LW and has FM instead.
Nice 12 transistor radio with European looks. Its exterior is based on the Schaub Lorenz and ITT radios of the early 1960s. Even the size is the same. Performance is not quite the same as the European radios. See Schaub Lorenz and ITT at my site.
© Hans Hilberink 1996-2001