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WIGGLING 'LITE' IN GUEST MODE

Troubleshooting ADSR/VCA
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Troubleshooting ADSR/VCA
Paradigm X
Hi Tony, I hope you are well.

I am trying to debug the adsr you saw in cambridge.

I have removed the 'mod' for now, so its a standard build.

After a bit of beeping out, I realised that i had the sock 4 board upside down - makes a massive difference! i didn't realise they had a polarity but obviously they do, doh! d'oh!

Thought id cracked it, but when i tested it, i get a thin distorted kind of sound, rather than the correct sound. i have a krisp1 to compare, so can make an audio recording of similar settings if that would help.

I checked all the ICs are correct, which they appear to be, and i swapped the THAT chip, but no difference.

Im a bit stuck as to what to look for at this point, so was wondering if you or anyone else had any ideas as to where to start looking?

i was thinking of removing the cheapo socket for the that and soldering direct as paul suggested?

Many thanks, regards
Ben
Synthbuilder
First thing, check the ADSR output is working correctly. So connect the module to control a filter cut-off, or VCO pitch via the ADSR output and ignore the VCA OUT for now. Check that it's doing the correct thing by comparing it to your working one. If it is, the THAT chip is fine and the EG part of the module is working.

That leaves the VCA part. Now unplug from the ADSR socket and plug the same jack plug into the VCA OUT. Does this modulate the filter or VCO in the same way as the raw ADSR output? If not then you have a problem with the VCA part. As usual suspect the wiring to the VCA IN and VCA OUT sockets before a fault on the board. If these are fine then check the soldering around U5, 6 & 7, and their associated parts.

Tony
Paradigm X
Brilliant. thanks so much, would have taken forever to work out how to test it.

Many thanks, ill try to give it a go tonight.

cheers, ben
Paradigm X
Synthbuilder wrote:
First thing, check the ADSR output is working correctly. So connect the module to control a filter cut-off, or VCO pitch via the ADSR output and ignore the VCA OUT for now. Check that it's doing the correct thing by comparing it to your working one. If it is, the THAT chip is fine and the EG part of the module is working.



Ok. so it failed this test. just get a series of static 'notes' (voltages i assume) almost like a step sequencer when using the adsr output to modulate VCO frequency. krisp1 on the same settings does what i expect an adsr to do.

so theres a problem on P1 on the schematic.

wow, already cut the problem in half.

im reasonably confident the wiring is good now, i did check continuity when i worked out the sock board problem, but will double check that, and swap out the cmos chips i guess as a starting point? if that still fails then perhaps try solderin the that chip in, the socket does feel a bit flimsy.

im away now for a couple of days but will check all those parts when i get a moment.

many thanks! cheers
Ben
Paradigm X
ok so ive changed the 4001 and 4052, and soldered the that chip directly to the board but no luck.

still checking things out, but can i check a couple of things please?

i used bc549c instead of bc550, i believe these are the same but can you confirm theyre ok?

i also used a hcf4001be instead of a cd4001, again thought the same but double checking.

i havent got any alternatives at the moment just more of the same types.

will try swapping out the opamps next i guess.

soldering looks ok, been over with magnifying glass but no obvious shorts/bad solders. also checked the caps, the tiny cog ones are impossible to read but all the others are correct.

many thanks
ben
Synthbuilder
Paradigm X wrote:
i used bc549c instead of bc550, i believe these are the same but can you confirm theyre ok?

i also used a hcf4001be instead of a cd4001, again thought the same but double checking.


Yes, both of those are fine.

What does the LED do when you trigger the module in normal mode? Does the sustain level change the brightness at all when it is triggered?

Are the A-D and S-R headers shorted out in the way described in the Builder's Guide? I guess they are but it can cause some odd problems if they are not.

Tony
Paradigm X
Hi Tony. thanks for your continuing patience!

From memory, the LED does a little blip then stays faint (but not off). Will have to double check tho.

also curious what the Loop mode is doing now, it seemed to work when i was messing with the mod. on my scope, which i admit i dont know how to use very well yet, the amplitude and frequency of the looping waveform did exactly what i thought it would do. have since removed that mod for now, although nice to know it works.

I am pretty sure the ADSR headers are shorted, i measured the resistance across them to be sure.

i double checked the sock wiring which seems to be correct.

Sorry, i reread your construction guide, which does confirm the bc549 are ok, i knew id read it somewhere.

I shall continue my efforts. I have replaced the tl074 on P1 of the schems but not tested it as of yet.

i have also got Pauls to compare to, but as its a full upgraded one im a bit hesitant to take it apart if necessary.

Many thanks, Ben
Paradigm X
heh, well many moons later i have had a chance to re-try this.

Swapping out the quad opamp seems (tentatively) to have fixed it! havent tried the vca part but the envelope itself works like the krisp1 one.

only problem is I now need another case!

many thanks!
Ben
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