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Nikko TRM-500 Amplifier



Generously build high quality amp made in Japan by Nikko Electric Co. Tokyo.


Front ^


Before the restore ^


Special futures:

This amp has a 4 channel option with extra adaptor.






User & service Manual:

Click here to download the manual with schematic in PDF format of the Nikko TRM-500.



Power-amp pcb ^



Power-amp section ^


Power transistors NEC ^

Power transistors Toshiba ^


Detail power supply ^


Pre- and power-amp interior ^


 pre-amp component-side pcb section ^



All electrolytic caps should be checked and exchanged when out of specs.
The main power caps are usually of good quality, but in case of flaws can be upgraded up to 10,000µF.
Check the power supply diodes.
Check the input transistors of the power amp section if they make noise.
Exchange the pots on the power board for 10 turns and align the power amp correctly.
You may heatsink the bare driver transistors as well as the pre-drivers.
The input transistors of the power amp section can be joint together with a copper heat-joint to get the DC-offset more stable.
Set the power transformer to 240V in Europe.
The input el-caps of the power amp section can be replaced by small true MKT capacitors (Rifa or Wima).
The power-supply diodes of this amp, may be exchanged for 100V - 10A diodes.
There are 2 versions of this amp produced: one international version with cinch sockets and one EU version with DIN sockets.
Consider a DC-sensing speaker protection-board, the amp has only AC & DC max. current protection.
Speaker wiring is rather thin and may be upgraded if you like.



New 10 turn pots for the DC-offset ^


Pre-amp pcb copper-side ^


Power caps & mains selector ^


Overview bottom inside ^


Back international version ^



Excellent sound, quite the same high quality as the Sansui AU-555 and AU-555A and other amplifiers of the same kind.





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© PE1MMK-ON9MMK Hans Hilberink last update:  21-03-2020.