Nikko TRM-300 seeking schematic/service manual

[ferguaj]

Hi

I'm a newbie here. I have a little Nikko TRM-300 with a distorted left channel. Before I start hauling it apart I was wondering if anyone has come across a schematic or service manual for it. I have checked all the usual spots but they only seem to have the higher models in the TRM lineup. So far all that I know is that the output SC1060's are fine. No recapping done yet. No loose wires visible inside. Solder points all seem fine on boards. Have cleaned all the pots and switches. Remains distorted on left regardless of input source.

Any help sourcing schematics or ideas for fix welcomed. Be patient with me please!

Thanks

Andrew

 

[mbz]

Regarding service manual you will need to find the closest thing and extrapolate?
Hifiengine has the TRM-210 and 500. Pick the one that looks similiar.

Regarding troubleshooting.
You've done the visual inspection and cleaned switches. Tried different inputs. Excellent!
You should check the caps for any stress (bulging, leakage, receeding top plastic sleeve).

Also, is the left channel distorted at all (low) volumes? Same through headphones?

Is there any noise when no source connected, try different volumes.

It is probably going to be a failing transistor, this is just a guess.

You could check the bias by carefully measuring that voltage between the output TR's
2 emitter resistors, see pic as example, from TRM-210


expect about 10-15mVdc, no signal input, minimum volume.
This will not be the problem, just provide an indication of the general health.

 

[dario54]

I have just found one of these NIKKOs in the trash recently.
Had no expectation, just started to clean it well, both inside and outside, DEOXIT and dry cleaner too, resolved all problems of suck switches, output RCAs are again shiny, no more dust inside.
Connected with headphones using FM as source, seemed working with no problems at all, connected with the CD player sounded very smooth, using a proper antenna, all the tuning section showed to be perfect.
Now the only trouble is in the phono output.
Nothing connect to it: no no noises, even at max volume.
Inserting a cable and the receiver emits a unpleasant hum which grows when turning louder the volume knob, and that before connecting my TT (working perfectly with any other amp or receiver.
Yes, a ground cable is connected too, problem is that the noise starts ONLY inserting a cable.
I tried already any RCA cable I have at hand, but always the same results, sometimes noise is louder sometimes is weaker.
Not having the schematics, and since the main board look very full of components, I look for suggestion on how to proceed, the unit otherwise is in very good shape and hate to trown away something that may be easily repaired.
Thanks for any help on this matter.