Brilliant! Thanks both for the speedy reply!
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Itās a bit of a hack job - my wonky DIY panel led to some issues with the pots and a few less CV inputs than indented, I had to retouch a lot of the soldering to get things going, and I still havenāt fixed the VCA section - but itās alive and the 1114 filter sounds incredible!
I thought Iād bitten off more than I could chew more than once, but with all the help from this thread and the info on the LMNC site itās somehow bleeping and blooping.
Iād definitely recommend this for anyone considering it. The glitchy, distorted tone works really well to give a 1 oscillator synth a huge sound! All I need now to get working on the envelope generator and Iāll have a fully fledged voice.
Thanks all!
Jack
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cool stuff!! looking good. glad you are persisting. it happens from time totirmenot knowing why something works, then getting fixed all part of the process 
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Yeah, this module rocks. Please post some sounds outta that thing!
Also,
Is that some solar frickin roadways i see?
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Hey there everyone. I just finished building the Filter Grrr but even after reflowing I canāt get the thing to work. The bottom left LED (2-colored) is bright green without anything plugged in so that probably means there is -12v constantly on there. If I switch the shelf itās supposed to make noise on its own and the LED beside it should show it but there is nothing. No noise and no light.
Could someone take a look at the board, maybe Iām missing something?
Where could I start to measure for faults?
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if the led is green probably means the attennuvewrter is stuck on and going to -12v like you say. if you look at the schematic in the section āfilter voltage controlā thatās that part of the circuit so ifs you measure on pin 14 of U1 itāll probably be a minus voltage as thats what is powering the led?
take out U1 see if pin 14 still shows a minus voltage
replace U1
check all the resistors around that. R11, R9, R6, RV1, RV2, R18 etc.
double check Q1 and Q3 are 2n3906
double check R17 is 100k.
check R19 is 100k
etc. im just looking at that part of the schematic and reading bits off to focus your attention on.
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maybe also these solder point can be suspicious ?
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Hi all,
Not sure if thatās the best place to ask (or if it has been asked before) I just wanted to check that I am understanding the schematic correctly.
Are pin 7 & 8 connected to V+/ 12v ?
Thanks !
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Pin 7 is connected to pin 5 of U2C, and pin 8 is connected to the FILTEROUTPUT label, and to the right hand pin of the resistor at the top that I canāt quite see the reference for.
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the V+ is an internal connection in the chip check out the pinout of the lm13700.ll symbol looks slightly different but youāll see the two collector pins of the internal transistors are wired to the V+
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All right , yes got it now. I did see this online but then I was struggling to understand why it needs to be displayed if it is āwiredā internally.
Thanks !!!
(I am always amazed that you are taking the time to answer silly questions. But it is much appreciated.)
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hey up all good! random threads I get email notification!!! all good happy to clear it up (Y)
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I got it working !!! It has got such a massive range of sounds !! Love it.
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bug hunting:
- have an output signal coming trough
- no or very dim LED-action at any resonance, trim level or shelf-setting
- it is self resonation in shelf-mode
- the trim-pot had problems (went crazy when touching it with a screwdriver) and i replaced it
- this is my 5th module (1163, 4710, 1157 & f-box). i thought i was making progress
from samās demo and Bpbbybās test i got the impression there should be MORE OUTPUT coming trough. the module is having barely any effect except dampening the signal at most settingsā¦ still searching these beautifull artifacts
I had a look at he shematic at the project page and started measuring. i found out that some of the 100K resistors i used measure at lower values e.g.: R11 at ~67k (r39&40 are far off too and there maybe others) could that be the problem? damn lowbudget supplies from the dark side of the moonā¦
before i start tearing my days work appart i thought iād ask for advice firstā¦
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Are you trying to measure resistances for parts in the circuit? That usually doesnāt work, in particular youāll often see lower resistances due to other loads in parallel.
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i measured different scenarios (i imagined):
- from left of resistor to right of resistor to check if the āpartā is up to spec (as in picture above)
- from point to point to see if there is any conductance that is āimpliedā in the shematic e.g. leg of LED to gnd or the other direction from the opposite leg to leg 14 or 13 of U1
- from leg 13 to 14 of U1
AND next time i make an unpopulated beauty-shot of the pcb for refference
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Yeah, your resistors are fine. Theyāre just in-circuit.
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Stupid idea but are you 100% sure that the VCA level is at the maximum ?
Also, it seems that the entrance level is affecting the overall sound quite dramatically (at least on my module). If the level is high and the clipping level is at max, then I get nearly no sound out of it.
What signal are you using to test it ?
Good luck !!
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Iāve just built this but have a wee bit of a strange issue.
Specifically, Iām getting no output at all.
When I plug in something to the output jack, both LEDs light up, but then the lower one goes off after a second. The top LED remains constant whatever position the switch is in.
Iām not really sure what the problem could be. Iāve re-seated the connector board to the jack sockets. I canāt see any obvious shorts or problems.
Is there anything specific I can/should test?
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Plot twist: I tried a different TL074 from a new batch of ICs I got, and none of them produce any results when I put them in. Not even the LED lighting up. So it seems like that batch might be bad, but it still doesnāt help diagnose the issue with the build originally. Could the LM13700 be dodgy and produce these kinds of results? Iām a bit stumped.
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