yep here we go. this is a single bank. however if you say the lfo’s all dont work if the lights are flashing then it may be the mix bus also.
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makes sense. it could do that as if the offset trim pot on one of the quad lfo boards are slightly offset itll cause a positie (or negative) voltage to go into the mix bus causing a light to light up. one lights up for positive voltage, the other for negative
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Super, cheers.
All have one LED on constantly, although the mix nob does attenuate the mix led.
So basically it’s full scale on the output one one half of the wave. LFO’s are all ok. did see some output on pin 5 of the LFO but could not make it change waveform.
Voltages all seemed fine on the 74’s and VCLFO.
Will work through it now I have the diagram. may be dodgy TLO74s, so may test them in the old LFO.
Must have done something common to all 4 bit seems odd.
Cheers
Rob
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I only have one installed on the jack board for testing, so no interaction.
Quite a way through metering it out , only realy got the CV’s to check over now and no obvious issues. 74’s are fine too.
I had a genius moment, I had not checked the -5V and the 79L05’s had never been needed on anything else so they were previously un-tested.
So plugged it in, wipped out the meter, put it on one of the -5v pot pins and lo and behold!!!
-5V 
I have confirmed good 0-5v swing on all the control inputs on the LFO, confirmed all the power, checked the LFO an 74’s work in another circuit. all that is practiacly left now is the output circuitry which mostly has metered out ok for values and continuity.
Perplexing…
Rob
hmm odd. do you have an oscilloscope? is there a way to check the pins on the electric druid chip? to see if there is ay output from that chip? it might help isolate the problem
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yeah got one of the little fnirisi ones which i find a bit of a pain, and an old dual Leader like the one you had ( salvaged ~20 years ago ) . so the next port of call was to work through the output of the chip and then through the output stage with the scope.
To err is human, to build four identically faulty units requires special skills.
Well it seems it’s probably not a mistake, two are now working. I removed a few resistors of one during tracing, and after puting them back it worked apart from one LED is now dead ( 2N3904 may have smoke as the magic stuff did escape at one point ) .
I reflowed the same resistors on another board and that now works.
Tried the same on the last two but no joy yet. will check the LFO is outputting like the others and then just concentrate on the output buffer circuit.
Cheers
Rob
all are sort of working, I had decided to put the trim at 50/50 as a starting point but this was a mistake. winding it right down got things going.
But it basically seems to be 4 lots of noise. I need to check it again and make sure the distort is right down but it sounds nothing like the single unit. Will try and get a vid.
Update 3/2/23
Not got back to checking why this is just noise…
But I recived some 16F1824’s from digi key today ( not that I realy need them ) and flashed my own LFO chip. Works as it should in the old single LFO moule.
Rigth 2 out of 4 are ok, one is unresposive to control nobs and the other is not gr8. time to re-flow…
So I’m trying to get the sync working on this but cant seem to get it to do anything. I basically want the LFO to reset using the gate out from my beatstep pro. Any suggestions to what I might be doing wrong?
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I only built the single lfo model but on mine the sync is a bit tricky, only works if I offset the gate voltage. It could be related to that.
I am not sure if the Sync reaction time of the chip is fast enough to be reacting to a single gate coming in… it also seem to take a bit of time to adjust on mine.
Thanks for the advice, I had another go today and used an envelope generator which I think worked. I still need to calibrate the S/H but haven’t got round to doing this yet. Just out of curiosity how do you normally control the sync in your own system?
My goal was to create some long bass sounds that have an LFO modulating the filter. I was hoping that I could use the sync so that each time a note is played the LFO resets allowing the modulation to be the same each time and not be halfway through a cycle. Hope this make sense. Cheers.
It does and this is an entirely reasonable thing to want to do. Ideally you should be able to sync the LFO using the same gate you control your envelope generator with. Syncing with the EG is a little problematic if the envelope attack time is long, in which case the sync doesn’t come until after the note has started.
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It’s a big build for certain. After this everything else (almost) is cake, albeit chewy cake. 
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Not sure if this has been covered, I somehow have a single board of this module due to a shipping mixup, wondering if it would work by itself by adding power and outputs on a proto board?
have a close look at the pictures on the project page. there are not many parts on the “jack board” just the usual power input stuff and a tl702 with family. the “output pins” on the single sub modules go directly to the jacks. the LFOs should be highly similar to the #1145 single LFO.
but i’m no expert, i just follow the instructions and successfully built one of these… mybe one of the seniors around here could back my bold claims
EDIT: have a look above, Sam posted the schematic of the connector board
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