I already thought that I blew the bass! :'-( But today I tested it again and it worked Ok... Wheh!
Also found a Sharp GF-700 from a local used goods -shop. First time I visited. There was also few others, small Aiwa and Panasonic, also a "long-but-small" -type Goldstar with vertical CD, some DUX sound machine and few others.
Now I'm fitting the amp inside the casing and start to think about rewiring and how to do proper Line In, using the original connectors. Should also invent a way to get the bass level knob in somewhere. Maybe I'll fit it in the voltage selector hole... will see. The amp fits like a glove, will fasten it with hot glue.
There is a lot of free space on the right side of the unit. I will remove the connectors and make direct wirings...
Removed the diodes, no use for them. In future, I may fit a higher amperage power supply. But for now, I'll see how it runs with the original...
EDIT:
Ohhh yeahh! Running on batteries now!
Not as loud as with the amps own adapter, distortion can be heard with "full blast". I did try with the original power adapter but I am having a bad noise problem. Will need to ground them together better and so on. Maybe I should remove the original amplifier circuits altogether, now they have the +voltage pin cut. Without the motor hooked up, no noise. Guess thats the culprit.
I took the line level (or should I say pre out) to the new amp from after resistors 3541 (R) and 3641 (L). They are located right before TDA2004 line inputs. Therefore I have full volume, bass, treble, balance and stereo controls!
Power led was not lid due to mixed leads
This was just the first try and I will try my best to make it as perfect as possible. Was thinking about fiddling with the switch on the side, to make "line in" -mode work like record would be pressed but motor wouldn't run.
And yes. The low end is a beast. I will do more testing tomorrow and crank it. Maybe a youtube too. Though no good microphone... or could I just use a boombox for it, make it record and use line out to record on a computer...