Intermittent preamp output problem

[Sleet]

So, I have this old G&K 210G solid state amp that I want to see if I can get it working again. When I feed some music from my MP3 player into the input, I can hear the song playing without it being hooked up to a speaker (load). It sounds a bit distorted, but it will cut out completely when I wiggle or press on the wired connections from the preamp to the amplifier circuit board. I did check for continuity of the wires and the connectors seem to be solid. The PCB for the amplifier appears to be okay no cracks or lifted traces around the connector. I have attached all the schematics for reference.

[Jon Snell]

This amplifier uses a transformer to connect to the speakers. Never use it without a speaker connected as the back EMF from the transformer can damage the output stage.
Plug a speaker in and check it properly following the signal back from the speaker ouptut to the signal input socket with your oscilloscope.
That will show you where the break in the signal is.
All you are hearing at present is the transformer vibrating under stress.

[Sleet]

Thanks for the information. I should have known better about the speaker. I will reset and hook up the speaker again. Hopefully, I haven't permanently damaged anything.