Broken E&MM Spectrum Synth

DIY STUFF
1

Hello! Sam here! I was recently given a slightly broken synth and I’m not really sure how to go about fixing it. Most of the keys don’t work and the keyboard controls are completely not working. So far, I have cleaned the knobs and front panel and touched up a few loose solder points (wires connected to the pots, LEDs and switches).

After these fixes, most of the keys now work and some of the key controls are working again (Glide and Tune). However, the envelope generator is almost entirely broken and some keys still don’t send out a signal.

As of now (3rd Aug) I don’t have the schematics and my schematic reading skills are still not the best. Does anyone have an idea on what I should do next? Also, should I bear in mind whatever I change could have an effect on its money value? - I’m not planning on selling it any time soon, but I really want to be careful and not break it further. Thanks for the feedback in my last post in the introduction thread by the way!

Also here is a pic of the synth:

20220803_132423
20220803_1324231920×887 150 KB

I will post more and some pics
of the inside :smile:

3 Likes
2

As of three days ago two people had posted links to the schematics.

4 Likes
3

Oh yes! Thanks! Completely forgot lol :sweat_smile:

4 Likes
4

I’d say one thing is to replace any electrolytic caps that show signs of leaking or bulging.

For the keys that don’t work it’s just a matter of finding and fixing bad connections and/or cleaning bad switch contacts or replacing switches.

For the envelope generator, now that you know where to find the schematics, you know which components are part of the EG and you can look for problems there. There are two envelope generators, are both malfunctioning? It’s hard to see how a single fault could break both. If one’s working and the other’s not then, after checking pin connections to make sure nothing’s shorted, you could try swapping the 3310 chips to see if that swaps which EG is working. (That’s assuming the chips are socketed of course.)

3 Likes