Amstrad CT-1 amp

[Token]

Hello everyone,


I'm not even an electronic beginner but I liked to share with you anyway. Also sorry for the bad english.
Since years I got a CT-1. It cames with a 464 on Ebay. It was useless until...
I have the idea to put it in my bathroom    It's there since 6 months, since I replaced the bath by a shower. I simply love it.
Few days ago, I opened a PCW topic. Somebody wrote I should try to put the mainboard on a 6128 keyboard. I wanted to clean it the hell, even inside then I though it could be cool to use the CT-1 for, and with the GT-65 above 


All this gave me a new idea.


Trying to use the amp from that radio for anything else. I have also a CTM, I liked to add sound, I'm using other computers with this monitor.
So what I did works, but the radio signal is mixed. I think it's possible to select a signal, maybe by cutting a pin and add a switch.
So, it's only ok if you tune somewhere there's almost nothing. It was clean before I put a monitor above, testing the 6128 sound output.
My audio cable takes a lot of sh!t  it's only good alone in my bathroom with a MP3 player...


tda 1083 is the little chip where I did the small soldering, a Telefunken in my CT-1.








I did an error on this, it worked (??) but was inverted.



Thanks Bryce.   (dirty I know, fast experiment, I might try other one with the case)



I used an old cable with stereo mini jack (3,35 TRS) cut it and soldered 2 parts. Right and left connected for mono ... on pin 9, ground (white cable) 11. As you see there's many other things. Doc for the chip here

http://pdf.datasheetcatalog.com/datasheets/320/377985_DS.pdf

[Bryce]

Nice little mod. Did you also cut the track on the PCB that was going to pin 9? If not, you'll still be picking up noise from the reciever circuitry.

Bryce.

[Token]

Thanks. I might try this. It seems easier/faster than removing the chip and bend the pin.
Then add a switch to select radio/line. So there's a little soldering on the PCB track.
Make a hole on the side, et voilà...

[Bryce]

Just an observation: You've said that you connected the Audio Inputs to pin 9 of the TDA1083, which would be correct. But in the photo (bottom of the PCB), the yellow and red wires are connected to pin 6?? and the white wire seems to be connected to pin 8??

Bryce.

Edit: Picture for clarification:

[Token]

  Damn, indeed. I don't get why I got sound. I'm going to cut the track etc, correct this non sense... Thanks Bryce

[Bryce]

Those connections probably would give you sound too. Just they would go through a lot of unnecessary filtering etc that might chnge the tone / volume. The GND connection especially.

Bryce.

[Token]

Ok, great help Bryce. Filter? Nice =]


I did a fast test, there's a lot more gain, and it doesn't mix with the radio (but maybe it's the gain)