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Hello,
I just built this one and it does nothing. Signal is not altered when switched on. It goes through just like when there is no sound effect. There is not sound oscillation.
Additionnal information:
– All 4Qs are matched and verified
– I replaced IC3 to make sure it was not defected
– Led goes on/off, no problem.
– Signal goes through if on or off
– Solder is properly done and build is clean
I have no idea what can be wrong
ThanksWhat jfets did you use if they’re 2N5952s
Did you use the trimmer to set the jfet gate voltages to just over 2v
They’re all connected so you only need to set one
If they’re not 2N5952s check the pinout is correct
Did you use the trimmer to set the jfet gate voltages to just over 2v
I guess you mean at #2 on IC3?
No use a small screwdriver to turn the trimmer TR1 until you get a reading of around 2 volts on Q1, 2, 3 and 4 gate pins
The gate pin is the bottom one as circled in red below first check what voltage you get on Q1 gate pin if it’s not around 2v set TR1 to the centre position and turn it clockwise in very small increments till you read between 2 and 2.3v on Q1 gate
As I say you only need to do Q1 all the 2N5952s gate pins are connected as you can see in the schematic
I set them all at 2,08v i hope it is ok. They show all the same voltage. Same issue, sound is not modified. Does it hurt if a bit higher like 2,3v ?
No it won’t hurt setting the voltage higher or lower the crucial thing to remember is the trimmer phasing range is very small so move it in tiny increments
With 5952s you should get phasing with the gates set from anything between around 1.7v to 2.3v, in my experience using 5952s the sweet spot is usually 2 to just over 2v but try from 1.5v and move as I say slowly play audio through the circuit as you do it and you should hear it kick in then adjust for the most pronounced phasing sound
Check you get an oscillating voltage on the LFO IC3 output pin 6 you can also check on lug 2 of the speed pot
I’ve misread your initial post I actually thought you were getting an oscillating voltage from the LFO
thanksq again. so i do not have oscilloscope hence cannot tell you what is happening right now on IC3/P6. i can only tell you voltage is 8,8v. Also before posting here i worked on this with a friend way more skilled than me and he already identified that IC3/P6 did not oscillate using oscilloscope. we also tried various voltage with the trimmer without luck (very slowly) i tried again right now to test for each increment (trimmer is actually not that difficult to fine tune)
Additionnaly i have tried the voltage on speed pot lug 2: Voltage does change goes from.. 2.1v and goes up slowly then can go down. the logic of this variation is difficult to understand for me.
also don’t you think we are missing something more obvious? something pretty stupid i would have done?
With the LFO not oscillating it’s obviously not going to work
The trimmer doesn’t directly affect the LFO voltage you can check pin 6 with your meter the voltage should oscillate
It could well be something simple like a poor connection or solder joint
The speed pot just controls the oscillation / modulation rate have it set at a slower speed when taking readings on lug 2
Post voltages for all your IC pins and the Q5 CBE also the voltage at the top side of the 3M9 R23 with no power to the circuit check resistance across R23 check that R24 is a 4K7 yellow purple black brown brown we can’t see it because of your wires
Make sure all your ICs are firmly locked into their sockets carefully them in until they click
- IC3/P6 voltage is 8,94v and does not oscillate (tested with classic multimeter)
- i have pushed harder the IC and had a few clicks showing they main not have been properly clicked
- R24 is 4,7k
- i just change R23 for a new one and R14 because i had some doubts
- check video for pot/lug2 test
- IC3/P1: 6,68v
- IC3/P2: 2,14v (reading starts at a higher value then stabilize)
- IC3/P3: 3,89v
- IC3/P4: 0v
- IC3/P5: 7,92v
- IC3/P6: 8,95v
- IC3/P7: 2,83v (reading starts at a higher value then stabilize)
- IC3/P8: 0v
- IC1/P1: 0v
- IC1/P2: 4,81v
- IC1/P3: 3,24v
- IC1/P4: 0v
- IC1/P5: 0v
- IC1/P6: 9,10v
- IC1/P7: 4,8v
- IC1/P8: 0v
- Ic2/P1: 4,8v
- ic2/P2: 4,8v
- ic2/P3: 4,7v
- ic2/P4: 9,10v
- Ic2/P5: 4,7v
- ic2/P6: 4,8v
- ic2/P7: 4,8v
- ic2/p8: 4,8v
- ic2/p9: 4,8v
- ic2/p10: 4,7v
- ic2/p11: 0v
- ic2/p12: 4,7v
- ic2/p13: 4,8v
- ic2/p14: 4,8v
- Q5 bottom pin ( on the board picture) : 4,8v
- Q5 middle: 4,23v
- Q5 top pin: 2,83v
- R23 top: 2,3v
Are you reading your IC pin numbers in the correct order
Pins on the left hand side are numbered top to bottom and the right hand side bottom to top
Oh I am so sorry about that, yes i know how to read this numbering in theory but clearly i got distracted 🙁 i read column by column, so after translation to correct reading method this makes:
- IC3/P6 voltage is 8,94v and does not oscillate (tested with classic multimeter)
- i have pushed harder the IC and had a few clicks showing they main not have been properly clicked
- R24 is 4,7k
- i just change R23 for a new one and R14 because i had some doubts
- ——————-
- IC3/P1: 6,68v
- IC3/P2: 2,14v (reading starts at a higher value then stabilize)
- IC3/P3: 3,89v
- IC3/P4: 0v
- IC3/P5: 0v
- IC3/P6: 2,83v (reading starts at a higher value then stabilize)
- IC3/P7: 8,95v
- IC3/P8: 7,92v
- —————-
- IC1/P1: 0v
- IC1/P2: 4,81v
- IC1/P3: 3,24v
- IC1/P4: 0v
- IC1/P5: 0v
- IC1/P6: 4,8v
- IC1/P7: 9,10v
- IC1/P8: 0v
- —————-
- Ic2/P1: 4,8v
- ic2/P2: 4,8v
- ic2/P3: 4,7v
- ic2/P4: 9,10v
- Ic2/P5: 4,7v
- ic2/P6: 4,8v
- ic2/P7: 4,8v
- ic2/p08: 4,8v
- ic2/p09: 4,8v
- ic2/p10: 4,7v
- ic2/p11: 0v
- ic2/p12: 4,7v
- ic2/p13: 4,8v
- ic2/p14: 4,8v
- —————–
- Q5 bottom pin ( on the board picture) : 4,8v
- Q5 middle: 4,23v
- Q5 top pin: 2,83v
- R23 top: 2,3v
IC 1 and 2 voltages look good
What PNP transistor are you using for Q5
I wouldn’t swap out any components unless you know they’re a problem you risk lifting solder pads etc with too much heat
The IC3 voltages we’re most interested in are the input pins 2, 3 and output pin 6
Although I said the trimmer doesn’t directly affect the LFO voltages it does affect the JFETs I don’t want to get into too much technical detail that I’m not 100% on myself but afaik basically the LFO oscillating output controls the resistance between the FETs source and drain pin via the gate the JFETs are being used as voltage controlled variable resistors
So what we’re trying to establish is that the LFO works and the FET gates are set to the correct voltage
As you’ll know FET parameters vary wildly even from the same batch hence why you need a matched set so they work together
What is the voltage on the other side of R23
We need to know for sure if the LFO is working pin 2 and 6 oscillating will confirm that
The speed pot works in conjunction with C8 to set the rate so as you turn the speed pot from slow to fast C8 charges and discharges at a different rate which you should see on those pins set the speed pot clockwise a little under a quarter turn then slowly turn it up and you should see a difference in the voltage oscillating rate
Troubleshooting is sometimes a long process but as I say you’re better checking everything before changing random components in the hope that it works as I’ve said it could well be a poor solder joint it’s just a process of elimination that eventually leads you to your fault
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