[sdiy] SOMA Lyra-8 vibrato stopped working

Adam Inglis 21pointy at tpg.com.au
Sat Mar 9 13:51:58 CET 2019


Have you contacted the company?   It looks like a small operation, perhaps the designer might help.

Two CD4093 chips might account for the two groups  of 4 oscillators if they’re like this one
https://noisehackerspace.com/create-simple-oscillator-nand-logic-cmos/ <https://noisehackerspace.com/create-simple-oscillator-nand-logic-cmos/>

but what chip does the vibrato circuit feature? It might be a 555 or a dual op amp.

Also, if a chip just smoked with no provocation have you checked all the PSU voltages? 

> On 9 Mar 2019, at 1:57 PM, frey at radioles.com wrote:
> 
> Adam and list, I have a multimeter and an oscilloscope. I tested continuity around the vibrato switch and it was ok. There is a trace off of a header that runs to 2 cd4093be ICs. I checked that when the vibrato is in the on position voltage at the vdd pin goes to 16v.
>  And, just now one of the two cd4093be chips released the magic smoke. Dang. This synth is bisymmetric meaning it has 2 groups of 4 oscillators, hence two ICs l suppose.
>  Can anyone point me in the direction of vibrato circuit schematics so I can try and figure out how this one works and where the components are I need to check?
>  Thanks. JoeF.
> 
> On Mar 7, 2019, 6:34 PM -0500, Adam Inglis <21pointy at tpg.com.au>, wrote:
>> What test gear do you have Joe?
>> If you’ve been fiddling and something has stopped working, might be good just to do some continuity tests around the connectors and those boards.
>> 
>> However, the pitch of the VCO must be seeing some voltage from the vibrato circuit - maybe the LFO has failed? Does the LFO work as it should on any other part of the synth, say, the filter?
>> 
>> A
>>> On 8 Mar 2019, at 8:10 AM, frey at radioles.com wrote:
>>> 
>>> Hello, I modified my Lyra-8 by adding switches to the touch contacts so I could have a single oscillator work when switched on. I did this without modifying the pcbs only wiring the switches in parallel with the contacts bolted to pads on the pcb.
>>> However, somehow in removing the pcbs to install the switches I have caused the vibrato switch to stop working. When I flip the vibrato switch on, the Lyra audio output frequency shifts upward but never back down and does not oscillate as a vibrato should.
>>> I have found on one of the pcbs a connector header that runs from board to board marked vib and if I trace it back I come to an IC CD4039. I mention this to see if it is a clue for some of you with experience troubleshooting what I should look for that may be malfunctioning. Should I see an oscillating voltage here or what?
>>> Any advice would be most helpful. JoeF.
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>> 

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