It is not functioning right if the output swings to +15V when cycling.
Ken's notes:
Adjustments on the VCS board are set to obtain a 0 to +5 volt level when
the unit is cycling, producing a 100Hz triangle wave. An oscilloscope is
required for this adjustment. In an oscilloscope is not available,
adjust for the least distorted sounding waveshape.
I guess that he means the single trimpot by "adjustments on the VCS
board". I built two of these and did not have any problems.
Richard Brewster
http://pugix.com
Ken's notes:
Adjustments on the VCS board are set to obtain a 0 to +5 volt level when
the unit is cycling, producing a 100Hz triangle wave. An oscilloscope is
required for this adjustment. In an oscilloscope is not available,
adjust for the least distorted sounding waveshape.
I guess that he means the single trimpot by "adjustments on the VCS
board". I built two of these and did not have any problems.
Richard Brewster
http://pugix.com
On 9/22/11 6:29 PM, scozbort wrote:
> Cheers Laurie, I appreciate you input!
>
> Its the main OUT that gets hot. And I'm using a REV1.0 PCB so the 220k resistors should be correct. I thought about sticking a resistor on the output but that would affect the cycle out as well, which does not need attenuation.
>
> Its sounding more like its functioning perfectly. Am I being over-cautious worrying about throwing (potentially) 15V slopes around the system?
>
> - Kevin
>
>
> --- In cgs_synth@yahoogroups.com, "Elby Designs"<elby_designs@...> wrote:
>> The END OUT output should be clamped to 5V because there is a zener diode in
>> that line. If that is the output you are having problems with then the zener
>> is either faulty, not fitted, or the wrong value.
>> The OUT output doesn't have any such protection and it is feasible for the
>> output to approach power rail levels as it is driven directly from the
>> output of an opamp. I will need to study the front end more to determine if
>> there is any internal clamping but it might be worth asking Ken what are the
>> normal output levels to be expected. Maybe this output needs a simple
>> resistor divider.
>> The transistors are standard and should fit the pcb as is.
>>
>> The only other problem I can see is that Ken has 4 x 220K listed in his BOM
>> and then says in the text that they should be 22K. I have supplied 220K
>>
>> Best Regards
>> Laurie Biddulph
>> Mobile: 0400 257 645
>> Web: www.elby-designs.com
>>
>> -----Original Message-----
>> From: cgs_synth@yahoogroups.com [mailto:cgs_synth@yahoogroups.com] On Behalf
>> Of scozbort
>> Sent: Friday, 23 September 2011 6:43 AM
>> To: cgs_synth@yahoogroups.com
>> Subject: [cgs_synth] Re: cgs75 hot voltage outputs
>>
>> OK here is some more info.
>>
>> Most people seem to have difficulty with the transistor pin-outs not
>> matching the circuit. I don't think this is the problem here. The module
>> functions perfectly (except for hot output), and the transistors were
>> supplied in an Elby kit. I have emailed Laurie to see if the transistors he
>> supplied are correct (can't seem to find a datasheet for them).
>>
>> Also the calibration trimmer does offset the hot output voltage, but no
>> where near enough. I was wondering if a 20 turn trimmer here would allow me
>> to drop the voltage of the output right down whilst still maintaining the
>> correct triangular waveshape?
>>
>> Like I said it only outputs high voltages when its being triggered.
>>
>> It's completely useful as it is, I just have to attenuate the output. Not
>> comfortable send 15v signals around the modular. Or do I not need to worry
>> about this at all? I know it distorts my VCAs pretty quick.
>>
>> Any help much appreciated!
>> - Kevin
>>
>> --- In cgs_synth@yahoogroups.com, "scozbort"<kevin.babbage@> wrote:
>>> Hi!
>>>
>>> Can't believe I only just found this place...
>>>
>>> I'm having an issue with my VCS build and hoping someone has come across
>> it before.
>>> When I use the trigger in and slow fall times the module outputs very hot
>> voltages - I think it would go to 15v if I let it.
>>> But in cycle mode it outputs normal voltages.
>>>
>>> I suspect a wiring fault but I can't see any mistakes, unless of course I
>> have misunderstood how to wire it up - which is likely!
>>> Hoping its an easy fix and thanks in advance
>>> - Kevin
>>>
>>
>>
>>
>> ------------------------------------
>>
>> The CGS Modular Synth home page: http://www.cgs.synth.net/
>> Yahoo! Groups Links
>>
>
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