A frustrated Motorola

[julie_m]

Yes, the green wires need to be joined together (a little tidying-up of the soldering would not go amiss, while the set is still in pieces). They are the earth returns, and you want as near as you can get to a perfect connection. You have already inserted some series resistance with the "live" side of the signal.

['LIVEWIRE?']

Here is a sketch showing how I add an 'aux-in' connection to stereo radios or radio/cassette players The procedure is the same for mono radios, except that a resistor of between 1 & 10 K is fitted in series with each channel, between the jack socket and 'radio/aux' switch. I may, time permitting!, post other diagrams/pictures later

[Newshound68]

So as It would happen I don't have a 470nf capacitor. Biggest non electrolytic is 220nf. Can I use that or not enough capacity?
Which is why I was curious as to how people came up with 470nf

[crackle]

Try it and see what it sounds like, or double up with 2 in parallel.

Mike

[Newshound68]

will do and report back.

[Hampus]

A too small capacitor will damp the high frequencies making the sound dull and muffled. An unneccesarily big capacitor will be more expensive and physically bigger but will cause no problems so long as it is "within reason".

This is calculated from circuit impedance, signal frequency and so on. A bit over my head but 470nf sounds reasonable. You can always try another value and see how it sounds.

[Newshound68]

I rigged it up on a breadboard as a test outside of the radio.

Now just got to be creative with finding a neat way of soldering in and keeping the resistors and capacitors tidy.

I was thinking of using some heat shrink to insulate once satisfied it's all working?

Sorry, meant to say: IT WORKS! VERY WELL!

[crackle]

That's good.
If there is not enough room in the radio I would get one of those little plastic boxes from somewhere like Maplin or Ebay to fit the components in.

Mike

[julie_m]

That's excellent!

Heat-shrink tubing would be one way of protecting your components from short-circuits. Alternatively, you could mount the parts on a small piece of Veroboard and fix this somewhere inside the set. Use a similar-sized piece of plastic cut from a CD box or something to insulate this from whatever is underneath it.