Technics SU-G70 clicks but doesn't display or sound

If the front panel display on your Technics SA-AX6 is not turning on even though you have replaced the display board and verified that the ribbon cable is not broken, there may be an issue with the power supply or the main control board. It's possible that a component on one of these boards has failed, preventing the display from receiving power or a signal. You may need to take the receiver to a professional repair shop for further diagnosis and repair.

That sounds suspiciously like an issue with speaker connections rather than amp output!

There are manuals and specs here including a Service Manual

https://www.google.com/search?q=technics+su-x840+user+manual

..

https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Technics..

Turn the mute switch off.

I do not know

The clicking sound will be a relay for the protection circuit. That could be faulty, but first check out the main devices on the main amp section. Those attached to the big heat sink. If you see a single IC amp that could well be faulty.

It sounds like the switch might be broken. It might need to be replaced.

Sir the problem of your unit is the power IC the other channel of this IC is already faulty. unplug the unit to the main AC outlet then remove the cover of your unit you will see a large aluminum plate the power IC is attach to that heat sink in order to fix this you should replace the IC. Or can you give me the part number of the IC so I can determine the pin configuration. Good day and best regards.

An amp will cut out if the output protection circuit kicks in. This circuit compares output power against the preset level. Each channel has it's own, independent protector. There are calculations that can be done, but for a novice the rule of thumb is to "never use a speaker with a power rating less than the amp AND a lower impedance than stated". Typically using a 4 ohm load on a 8 ohm system is inviting disaster. Even if the system does not become a smoke generator, you might notice that though "louder", the sound quality is deteriorated. Many "audiophiles" often hook up some combinations of speakers to have "surround" without really understanding that the collective impedance actually changes (generally lowers).