Yamaha SK20 signal bleed in mixer section

Pulling out your hair? Don't know what to do or where to go? Ask in here.
Forum rules
READ: VSE Board-Wide Rules and Guidelines

If your Help request has been solved, please edit your first post in order to select the Image Topic Icon to let others know your topic has been solved.

Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Tue Jan 31, 2017 7:31 pm

Hi,

My SK20 has this issue where the Strings signal is audible in the Polysynth mixer output.

To explain a little better, there is a mixer section for Organ, Strings, and Polysynth before the Master Volume and main output. When the String section fader is set to its minimum it can still be heard through the Polysynth section. So when I have the Polysynth fader up and play the keyboard, the Strings section can be heard underneath the Polysynth output at a low volume. It also appears to overdrive the output so that it slightly distorts.

There is a trim pot for the Strings signal level adjustment which can be seen on pages 16 and 46 in the schematics. I wonder if adjusting this may do the trick or whether the issue is happening elsewhere along the circuit.

https://elektrotanya.com/yamaha_sk20_sy ... nload.html

Any help would be very much appreciated!
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship

Re: Yamaha SK20 signal bleed in mixer section

Postby synthchaser » Sun Feb 19, 2017 7:40 am

You can only hear it with Polysynth on, not organ?
synthchaser
Newbie
Newbie
 
Posts: 30
Joined: Fri Jun 17, 2016 2:49 pm

Re: Yamaha SK20 signal bleed in mixer section

Postby synthchaser » Sun Feb 19, 2017 8:01 am

I just looked at the schematic. Yeah, adjusting that trimmer should make a difference.
synthchaser
Newbie
Newbie
 
Posts: 30
Joined: Fri Jun 17, 2016 2:49 pm

Re: Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Sun Feb 19, 2017 3:56 pm

Hi,

Thanks. Yeah, it's only audible with the polysynth on.
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship

Re: Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Fri Feb 24, 2017 8:31 pm

It seems that that trim pot only adjusts the Strings signal level into the Mixed output. Adjusting it makes no difference to the bleed unfortunately. Any other ideas?

:)
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship

Re: Yamaha SK20 signal bleed in mixer section

Postby Broadwave » Sat Feb 25, 2017 10:06 am

Can I suggest taking a look at the volume foot pedal input for the string section.
User avatar
Broadwave
Active Member
Active Member
 
Posts: 367
Joined: Wed Sep 14, 2011 10:50 am
Location: Manchester UK
Real name: Andy
Gear: Kronos 2-88, System 8, MX49, Ultranova, BroadWAVE ARP 2600EX, BroadWAVE Modular, BroadWAVE Sparta, BroadWAVE Minimoog, and some guitars

Re: Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Sat Feb 25, 2017 10:44 am

Thanks. Is this on the JK board? I did think about that, actually. But I can't see why it would cause the signal from one section to bleed into the other. Why might this be?

Just to be clear as to what is happening (I realise a text description is not ideal!), the bleed occurs only on the Polysynth mixer slider. If I set the Polysynth so that it outputs nothing (ie. ADSR all set to 0, filter set to lowest, etc.) and set the Polysynth mixer slider up and all the other sliders down, when I depress any keys I can hear the String section coming through the output.

If I do the same with the Organ section, the problem doesn't occur.

As far as i can tell, both the Polysynth and Strings sections share the same tone generator. It seems to me that somewhere along the circuit there's an issue with isolating the Strings signal from the Polysynth one (obviously), but the question is where this might be happening...
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship

Re: Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Sat Feb 25, 2017 1:31 pm

OK, I checked the volume pedal input. There's strange behaviour there. I plugged in a Roland EV-5 foot pedal and at first it altered the volume of the respective sections (String or Mixed). Then it ceased affecting the volume. There was a smell of solder/component burn coming from the synth. There was a similar smell emanating from the synth last night when I was checking it as well.

So now when the volume pedal is plugged into either of the pedal input jacks, the respective sections are muted. Very odd.

I opened up the synth and took out the JK board but it looks fine. No obvious damage to either of the ICs and the caps all seem to be ok.
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship

Re: Yamaha SK20 signal bleed in mixer section

Postby pinksoir » Sat Feb 25, 2017 3:03 pm

New issue discovered.

When the synth was plugged in for a while the transformer began to smoke. Is this a PSU issue?

The synth wasn't powered on, only plugged in (it had been powered on previously).
"I think it would be egotistical of me to say, 'I thought of it'. What happened is, I opened my mind up and the idea came through and into my head." - Bob Moog

User avatar
pinksoir
Junior Member
Junior Member
 
Posts: 187
Joined: Thu Dec 08, 2011 12:58 am
Location: Ireland
Real name: Karl
Gear: Korg Volca Keys,
Korg Polysix,
Roland JX3P,
Teisco SX-400 ,
Yamaha CS-15,
Yamaha SK20.
Band: Bear Worship


Return to HELP!

Who is online

Users browsing this forum: No registered users and 1 guest