[sdiy] problems going from breadbaord to pcb/solder

Sun Aug 16 17:23:35 CEST 2009

Its OK John... I took my meds today :^)...

The layout can be an issue. It is probably NOT resistance (solderless
breadboards are not that bad...) It might be capacitive effects, that can
happen even as a component issue (lots of CMOS chips need a little
capacitor on the gates)

Is the circuit adequately decoupled (caps?)

Are there places where the input traces pass near output traces, that can
cause inductive or capcitive coupling...

Is this a home-etched board ? Look for open traces (hairline cracks) or even
under-etch conditions that might make the impedances too low (this is a famous
problem for S/H and other very sensitive circuits (like uhhh... expos ?)

H^) harry

----- Original Message -----
From: Dan Snazelle <subjectivity at hotmail.com>
To: dixon at interchange.ubc.ca, synth-diy at dropmix.xs4all.nl
Sent: Sun, 16 Aug 2009 10:34:55 -0400 (EDT)
Subject: RE: [sdiy] problems going from breadbaord to pcb/solder

appreciate the comments!

once again, this is a friends project not mine, so he really appreciates the comments.

one thing i should point out

he is NOT using rays expo.

he is using his own expo design which always worked very well on breadboard when the vco was on breadboard.

what he is doing now (the problem situation)

is running the WORKING expo into the soldered VCO CORE

the core is the issue. (as the expo works fine for all other cores)

once again, i thought maybe the issue was a difference in capacitance or resistance between soldered and 
breadboarded...i have heard of people having to add small amounts of capacitance (or is it remove) from final pcbs...or is this gobbolygook?

thanks again

--------------------------------------------
check out various dan music at:

 http://www.myspace.com/lossnyc  

(updated monthly)

http://www.soundclick.com/lossnyc.htm

http://www.indie911.com/dan-snazelle

(or for techno) http://www.myspace.com/snazelle

ALSO check out Dan synth/Fx projects:

AUDIO ARK:

www.youtube.com/watch?v=TJRpvaOcUic

www.youtube.com/watch?v=BqIa_lXQNTA&feature=channel_page

www.youtube.com/watch?v=V4nJPjGgOcU&feature=channel_page

and soundtrack/design work:

NEW: check out Dan's sound design from the 1998 award winning film SAFARI by catherine chalmers

http://www.catherinechalmers.com/videos.cfm 

> Date: Sat, 15 Aug 2009 22:42:17 -0700
> From: dixon at interchange.ubc.ca
> Subject: RE: [sdiy] problems going from breadbaord to pcb/solder
> To: jays at aracnet.com; subjectivity at hotmail.com; synth-diy at dropmix.xs4all.nl
> 
> Two comments about this expo/VCLFO/breadboard issue:
> 
> 1.  I've built lots of circuits on breadboards, and they have all worked
> more or less exactly the same once committed to PCB.  I don't think this is
> an issue.
> 
> 2.  I haven't analyzed Ray's circuit in detail, but I must say I don't
> really understand why the expo converter is configured that way, with one
> 3904 of the pair sinking current from the base of a 3906 which sources
> current to the OTA.  One would typically just source current directly from
> one 3906 of a pair, with no 3904s at all.  An excellent example of this
> simpler, more straightforward plan, which I have used in several VCOs and
> (altered slightly for higher source current) in a 4-pole VCLPF, is the expo
> converter from Thomas Henry's VCO-1.  The schematic can be found on Scott
> Stites's site:
> 
> http://mypeoplepc.com/members/scottnoanh/buildingthevco1/
> 
> In fact, this is an excellent circuit to analyze in order to completely
> understand just exactly what an expo converter is doing, and why.  This is
> an activity which I think we all must eventually undertake at some point in
> our synth-diy careers.
> 
> 
>> I've played with LM13700 based LFO cores some and have seen the same
>> problems. Maybe the cases are the same ones that I've seen. I'm assuming
>> there is an expo converter in there too. If not what is said applies to
>> whatever is supplying the current to the OTA Iabc pin.
>> 
>> The overall problem sounds like the current that controls the OTA gain (ie
>> freq) is going down to the point where it is shutting off the OTA
>> completely
>> or to the point there isn't enough signal or slew to trigger the
>> comparator.
>> Also when the current gets really low (ie low freq) the offset of the OTA
>> becomes a factor and that effects the symmetry. Some people had symmetry
>> problems when the op-amp they used in the ASM1 LFO had a large offset. So
>> I'd check the expo converter out and make sure that it was working
>> properly
>> and all the right resistor values are in there. If there is a current
>> limiting resistor in between the expo and Iabc pin check and make sure
>> that
>> is the correct value. For a LFO I wouldn't suspect there would be any
>> issues
>> signal feed through in the wiring effecting the circuit. Might also add an
>> offset trim to the OTA integrator for more dynamic range if it is an expo
>> controlled LFO.
>> 
>> Best of luck.
>> Jay S.
>> 
>>> -----Original Message-----
>>> From: synth-diy-bounces at dropmix.xs4all.nl
>>> [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Dan Snazelle
>>> Sent: Saturday, August 15, 2009 3:36 PM
>>> To: synth-diy at dropmix.xs4all.nl
>>> Subject: [sdiy] problems going from breadbaord to pcb/solder
>>>
>>>
>>>
>>> a friend of mine has been working on a vclfo partially based on
>>> the ray wilson VCLFO.
>>>
>>> it uses a triangle core with a lm13700, an integrator, and a
>>> tl072 comprator
>>>
>>> it worked without ANY problem on the breadboard
>>>
>>> however, when he soldered it up on perfboard the following problems
>> arose:
>>>
>>> 1. the symetry is off. mainly as the oscillator gets slower and
>>> slower, the symmetry falls out of line. it is fine at higher speeds
>>>
>>> 2. at lower speeds, the oscillation dies. (at speeds which work
>>> on the breadboard)
>>>
>>>
>>> I told him to try changing the hysteresis resistor value and cap
>>> on the comparator and this DID help somewhat (it kept the osc from
>> dying)
>>>
>>> however, things are still not quite right.
>>>
>>> IS THIS due to the difference between the capacitance on a
>>> breadboard and the capacictance on a soldered board?
>>>
>>> or could it be something else?
>>>
>>> anyone have any ideas on how to save this?
>>>
>>> i am very interested in the results as I will soon be moving some
>>> of my projects from breadboard
>>> to finished pcbs
>>>
>>>
>>> thanks so much
>>>
>>>
>>>
>>> --------------------------------------------
>>> check out various dan music at:
>>>
>>>  http://www.myspace.com/lossnyc
>>>
>>> (updated monthly)
>>>
>>> http://www.soundclick.com/lossnyc.htm
>>>
>>>
>>>
>>> http://www.indie911.com/dan-snazelle
>>>
>>> (or for techno) http://www.myspace.com/snazelle
>>>
>>> ALSO check out Dan synth/Fx projects:
>>>
>>> AUDIO ARK:
>>>
>>> www.youtube.com/watch?v=TJRpvaOcUic
>>>
>>> www.youtube.com/watch?v=BqIa_lXQNTA&feature=channel_page
>>>
>>> www.youtube.com/watch?v=V4nJPjGgOcU&feature=channel_page
>>>
>>> and soundtrack/design work:
>>>
>>> NEW: check out Dan's sound design from the 1998 award winning
>>> film SAFARI by catherine chalmers
>>>
>>> http://www.catherinechalmers.com/videos.cfm
>>>
>>>
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>>
>> 
>> 
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 

_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy