Fostex X26 multitrack tape recorder with no sound

[indiependente]

Hello,
I'm trying to repair an old Fostex X26 multitrack tape recorder. I've managed to change the belts for new ones and have the mechanical parts working. Now the problem is that no sound is coming out from headphones, line out or monitor out either when playing a cassette or when monitoring the inputs. I would like to ask for some tips in order to understand where the problem might be. Visually everything seems to be Ok. I've disassembled all the electronic boards and I can't see any obvious evidence of a problem. Every component seems Ok, no signs of over heating, all still well soldered. So how can I track the signal to understand in which block might be the problem? I'm guessing it might be on mixing or amplification because of having no sound either from playing, recording or monitoring. Could the power adapter also be the cause? I'm not using the original one, just a casual one with several choices for voltage output.
I have very basic knowledge of electronics, I don't have an oscilloscope but I have a multimeter.
Thank you so much in advance.
Cheers!

 

[Slouching Raymond]

First thing is does it have power?
It may operate on just plus, or both plus and minus voltages.
Look for the big electrolytic capacitors, and measure accross them.
That would give you some idea.
Because it is an audio sytem, you could use another external audio amp to listen in on the signal points.
Connect the external amp ground to the ground of the Fostex, then probe the audio circuit with the external amp's audio input signal.
The external amp will probably already be-decoupled with a capacitor.