Vintage Synth Repair

hello, I have a problem with my jx-8p. i think one of the 6 voices has a problem with osc2. every 6th sound is playing osc1 with the correct vokume, osc2 is also playing but lower. and this only happens when psc2 is switched to sawtooth. when i switch to square, osc1+2 are equal and there�s no problem. so this should not be a problem of the osc? any idea where to start the search? thank you, regards, michael

I had a similar problem with a JX3P. There is a test mode where you can go through each of the 6 channels to confirm which is at fault. Once confirmed check all components around the op-amp that deals with the square to ramp (saw) conversion on that channel. I was able to replace the op-amp & re-flow all solder joints around that area with good results. Another thing worth mentioning is that there is a CV controlling that op-amp's amplitude - this adjusts the ramp amplitude throughout the range of the keyboard, you can read up on how Roland DCO's work here which will help - http://www.electricdruid.net/index.php?page=info.junodcos

hope this helps

Nick



________________________________
 From: blatnik_michael <blatnik_michael@...>
To: vintagesynthrepair@yahoogroups.com 
Sent: Monday, 22 April 2013, 8:49
Subject: [vintagesynthrepair] Voice Problem with my JX-8p
 


  
hello, I have a problem with my jx-8p. i think one of the 6 voices has a problem with osc2. every 6th sound is playing osc1 with the correct vokume, osc2 is also playing but lower. and this only happens when psc2 is switched to sawtooth. when i switch to square, osc1+2 are equal and there´s no problem. so this should not be a problem of the osc? any idea where to start the search? thank you, regards, michael

Hi, thank you very much, also for the link (this helps:)). i´ll have a look
Michael




________________________________
 Von: Nick Bell <mckenzie126@...>
An: "vintagesynthrepair@yahoogroups.com" <vintagesynthrepair@yahoogroups.com> 
Gesendet: 15:59 Montag, 22.April 2013
Betreff: Re: [vintagesynthrepair] Voice Problem with my JX-8p
 


  
I had a similar problem with a JX3P. There is a test mode where you can go through each of the 6 channels to confirm which is at fault. Once confirmed check all components around the op-amp that deals with the square to ramp (saw) conversion on that channel. I was able to replace the op-amp & re-flow all solder joints around that area with good results. Another thing worth mentioning is that there is a CV controlling that op-amp's amplitude - this adjusts the ramp amplitude throughout the range of the keyboard, you can read up on how Roland DCO's work here which will help - http://www.electricdruid.net/index.php?page=info.junodcos

hope this helps

Nick



________________________________
 From: blatnik_michael <blatnik_michael@...>
To: vintagesynthrepair@yahoogroups.com 
Sent: Monday, 22 April 2013, 8:49
Subject: [vintagesynthrepair] Voice Problem with my JX-8p
 


  
hello, I have a problem with my jx-8p. i think one of the 6 voices has a problem with osc2. every 6th sound is playing osc1 with the correct vokume, osc2 is also playing but lower. and this only happens when psc2 is switched to sawtooth. when i switch to square, osc1+2 are equal and there´s no problem. so this should not be a problem of the osc? any idea where to start the search? thank you, regards, michael