electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software » YuSynth
Help troubleshooting Dual Gate Slew
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [7 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
dstrength



Joined: May 23, 2010
Posts: 17
Location: Mobile, Alabama, USA

PostPosted: Tue Feb 18, 2014 1:22 pm    Post subject: Help troubleshooting Dual Gate Slew Reply with quote  Mark this post and the followings unread

I'm troubleshooting a Dual Gated Slew module, and both sections 1 and 2 are exhibiting the same behavior:

1) In LIN mode, the slew time is very short even at values of 1M on P1.

2) In LOG Mode, the slew time works normal, but the rise / fall direction switch doesn't seem to affect the slew. That is, I get slew in both directions all of the time. (The direction seems to work in LIN mode, but it's hard to tell since the slew time is so short.)

Now, I've noticed that I used BF245B instead of BF245C. I realize the B has a lower gate-source voltage range and a lower zero-gate-voltage drain current than C. But, I'm not sure how / if I can adjust the circuit to utilize the BF245B...or if it is even related to the problem.

Any ideas or suggestions?
Back to top
View user's profile Send private message
yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Sat Feb 22, 2014 9:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Since they share the same cap it is normal that the LIN slew is faster than the EXP slew.
The RISE/FALL switch definitely should give a different behaviour, check that your diodes are not dead (short-cut) and correctly polarized.

_________________
Yves
Back to top
View user's profile Send private message Visit poster's website
Gypsum Fantastic



Joined: Mar 09, 2017
Posts: 7
Location: Sheffield, UK

PostPosted: Tue May 22, 2018 12:44 pm    Post subject: Re: Help troubleshooting Dual Gate Slew Reply with quote  Mark this post and the followings unread

I'm really very sorry to resurrect such an old thread, but this part of your post (below) is an exact description of the problem I'm seeing. I think my dual slew works fine apart from this one issue.

If you're still there, did you ever work out a solution? Anyone else have any suggestions?

dstrength wrote:

2) In LOG Mode, the slew time works normal, but the rise / fall direction switch doesn't seem to affect the slew. That is, I get slew in both directions all of the time. (The direction seems to work in LIN mode, but it's hard to tell since the slew time is so short.)
Back to top
View user's profile Send private message
g.gabba



Joined: Nov 29, 2008
Posts: 365
Location: berlin
Audio files: 23

PostPosted: Tue May 22, 2018 11:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

could you provide a link to the refering schematic?
Back to top
View user's profile Send private message
Gypsum Fantastic



Joined: Mar 09, 2017
Posts: 7
Location: Sheffield, UK

PostPosted: Tue May 22, 2018 11:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

g.gabba wrote:
could you provide a link to the refering schematic?


Thanks for the reply.

Sure. Here’s Yves’ page about it in general http://yusynth.net/Modular/EN/DUALSLEW/index.html

This is the schematic from that page http://yusynth.net/Modular/Commun/DUALSLEW/DualSlew-sch.gif
Back to top
View user's profile Send private message
g.gabba



Joined: Nov 29, 2008
Posts: 365
Location: berlin
Audio files: 23

PostPosted: Thu May 24, 2018 10:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,
i would beginn with shortening the two contacts used on SW2-2,
i would do this to test if Q1 is shortening out P1 permanently,
in adition i would disconnect SW-1 just to make shure there is no extra source of trouble

if Q1 is shortening out P1 permanently, the lin and log mode now both have very short rise and fall times

happy troubleshooting...
Back to top
View user's profile Send private message
Gypsum Fantastic



Joined: Mar 09, 2017
Posts: 7
Location: Sheffield, UK

PostPosted: Thu Jun 14, 2018 1:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK so I had a bit more time to troubleshoot the problem.

I'm slightly embarrassed to say that I think the module was working the way it's supposed to work all along.

Even with the slew direction switch in the "up only" position, you still can hear a pronounced portamento effect in the down direction (and vice versa), especially with the crazy extremely long settings I was using to troubleshoot.

I think it's because of the forward voltage on a 1N4148 is comparatively large and this voltage mainly dissipates via the 1MΩ rate-setting potentiometer. Or something like that. *shrug*

I replaced D1, D2, D5 & D6 with a lower forward voltage type (BAT43 Schottky) which has improved things.

Main thing is it's working as intended, I suppose.

Thanks to everyone who contributed.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [7 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » YuSynth
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use