AKAI MG-614 - mixer/recorder help needed!

[the fuhz]

Hello all,
I believe this is my first post. I am not entirely sure if my question is in the right forum, if not, please let me know.

Anyway, I am having problems with an Akai MG-614 (6 channel, 4 track) cassette recorder.

In terms of my abilities, I have the skills to replace parts (capacitors, resistors, transistors, etc). However, diagnosing which ones need replacing is beyond me. Unless it was visibly broken or burned up, I would not know how to test it.

I am hoping to learn a few things I can try to help narrow down the location of the problems.

With that being said, this is what I am dealing with....


-One of the mixer channels has a hiss with random crackle (this is without anything plugged into the input). I am almost positive that the problem is in the preamp section. I can make the hiss better or worse by changing the EQ. However, when the EQ is turned off, the noise is still present.


-Track #3 records with a loud hum/buzz. The instrument will be there, but overpowered by the noise.
When playing a 4 track tape (which has been recorded on another 4 track machine) it will playback fine and there is no noise appearing on the track in question. However, when trying to record its own tapes, the track has buzzing noises.


-The unit has four line-level volume indicators (green and red lights). They can be switched to display either 'Master' or 'Line' levels. When set to 'Master', the right channel level indicator is showing considerably less amount of the volume that the left channel has (even though I can hear both evenly).
What is strange is that these same level indicators work correctly when set to the 'track' setting (where each individual track is displayed individually through indicators 1 through 4).


Does anyone have any ideas on what I should try doing first? Do any of these problems sound related to each other? Any help would be most appreciated.

For whatever its worth, I have full schematics on the unit. But there was no troubleshoot in the service manual.

many thanks,
tf