Ground prong missing from power plug (Yamaha CS-5)

patrickvf1976 · Joined: Aug 08, 2011 Posts: 135 Location: Gig Harbor

So I have this Yamaha CS-5 synth and I have concerns about the plug as it seems to be missing something (ground prong?). It seems to be the kind that should have three prongs (ground and the other two), but the ground prong was missing and oddly enough both power prongs are the same size (not fat/slim). I haven't seen that before on a three prong plug. I have all my gear plugged in a surge protected power strip and the synth seems to work fine that way but I'm still having concerns about it knowing that ground prongs are there for a reason if that thing ever had one. Can I continue to power the synth this way since it's plugged in a surge protected source or should I keep it unplugged until the plug has been replaced? Any suggestions?

Osal · Joined: Aug 16, 2011 Posts: 107 Location: Here

Hey patrickvf1976,

This earth pin has two functions:
It references the ground of the electronic circuit to the same level than the other devices of your studio, the earth.
It provides safeness. For example, the front panels, if they are conductive, must be connected to the earth pin. In this way, if ever, accidentally, a cable with mains electricity touches this front-panel it will be shorted to earth.

I suggest you replace the connector.

patrickvf1976 · Joined: Aug 08, 2011 Posts: 135 Location: Gig Harbor

That's all I needed to hear. I'll get one from the nearest ACE store tomorrow. Just one more question though - are there any replacement plugs around that don't require to be soldered? My soldering skills are, let's just say sub par.

Osal · Joined: Aug 16, 2011 Posts: 107 Location: Here

Yes, I think that they are with screws. But I would tin the wires ends before.

Osal · Joined: Aug 16, 2011 Posts: 107 Location: Here

This is a video with a European connector, but you can see how it is done. It is important that the black insulator, in the video, is firmly held, to avoid mechanical stress to the connections.
http://www.youtube.com/watch?v=Di_AcbLSjfs

patrickvf1976 · Joined: Aug 08, 2011 Posts: 135 Location: Gig Harbor

Ok, fixed it, and it works! Now I have one more question about the synth itself - is the any way to frequency-modulate the filter by utilizing any of the cv/gate inputs? maybe my routing the output to CV or EXT IN and fine tune the trigger level? Or would this result in some kind of FM feedback mess?

Osal · Joined: Aug 16, 2011 Posts: 107 Location: Here

Do you have any user manual, service manual, schematics, pictures of front panel/rear panel showing labels, etc about this synthesizer?

patrickvf1976 · Joined: Aug 08, 2011 Posts: 135 Location: Gig Harbor

Nope, but from what I remember (I'm not at home right now) the rear has ports for External In, trigger in/out, CV in/out and Output. On the upper left part of the front panel is a small section where you can dial in the trigger level and select between Ext. In and Noise. That's all I can tell for now.

PS: I found a rear shot of the synth:
http://www.google.com/imgres?start=124&hl=en&tbo=d&biw=976&bih=734&tbm=isch&tbnid=tSzLLax2aiy5WM:&imgrefurl=http://www.flickr.com/photos/matrixsynth/2646834041/&docid=q0PTTD42QIUHvM&itg=1&imgurl=http://farm3.staticflickr.com/2182/2646834041_26e3377059_z.jpg%253Fzz%253D1&w=640&h=426&ei=RDH0UN5lx5WIAqiZgPgO&zoom=1&iact=rc&dur=320&sig=113164548905376655465&page=7&tbnh=136&tbnw=206&ndsp=22&ved=1t:429,r:32,s:100,i:100&tx=116&ty=57

and the front panel:
http://www.google.com/imgres?start=124&hl=en&tbo=d&biw=976&bih=734&tbm=isch&tbnid=C6QxtSlFxFnWDM:&imgrefurl=http://m.matrixsynth.com/2011/06/yamaha-cs5-analogue-synthesizer.html&docid=al43ZkqMMOYmUM&imgurl=http://3.bp.blogspot.com/-Vjr6OEji5x8/TgtehXMQabI/AAAAAAACqOc/xtc7u9_gEFA/s1600/cs2.jpg&w=1024&h=758&ei=RDH0UN5lx5WIAqiZgPgO&zoom=1&iact=rc&dur=359&sig=113164548905376655465&page=7&tbnh=130&tbnw=195&ndsp=22&ved=1t:429,r:36,s:100,i:112&tx=102&ty=77

Osal · Joined: Aug 16, 2011 Posts: 107 Location: Here

The user manual:
http://www.synthfool.com/docs/Yamaha/CS_Series/Yamaha%20CS-5%20Owners%20Manual.pdf
The service manual:
http://elektrotanya.com/yamaha_cs-5_synthesizer_sm.pdf/download.html

Accordingly the block diagram, the control CV affects both, the oscillator and the filter, thus I don't think that it will be very useful for audio modulation.
Furthermore, the response of the control CV in is 0.125V to 4V so the negative part of the wave will not get response.

The chip is fed with a +/-15V power supply and you can guess that it could stand inputs up those values, but we don't know for sure. In the schematics you can not see any input protection. Maybe is a simplified schematic.
The chip must be very difficult to achieve if you damage it.

I would use it only for what it was designed and I would avoid any experiments.

patrickvf1976 · Joined: Aug 08, 2011 Posts: 135 Location: Gig Harbor

Interesting. I do agree about using the synth's features as intended, however I found out about a neat trick where you use an audio splitter to route the output back into ext in and get some wild filter feedback out of it. I was wondering if that trick would work with routing the output to CV IN, hence the question in the first place. Thanks for your advice, having a lot of fun with the synth so far.