@billy
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If you’re going to try a parallel capacitor I’d say 100n for hf noise there’s already the 100u in parallel with the voltage divider
I’d use the unscientific method of dabbing your finger on and off the op amps to see if you can narrow it down without hearing it we don’t know if it’s oscillation
Do you have the R12 jumper on a switch if so does it make the noise in the normal position
Post an image somebody might see something I know I’ve missed incorrect values etc after multiple checks it’s easily done
What pickups are in your guitar is your power supply filtered and regulated
What transistors did you use for your forum vibe some layouts show the original Japanese transistor pinout where the collector is the centre pin it looks like the forum vibe pinout is EBC with the dot at E on the pcb image so if you’ve used Japanese 2SC types then it could be that
If I’ve had trouble with univibe builds it’s usually that where I’ve swapped transistor types to more modern easier to find replacements then forgotten about the different pinout
For the vibe I’d try a 100K trimmer in place of R14 and lower the resistance across it to see if that increases the vibrato effect
I think it should work if you look at the forum vibe schematic here although it uses transistors and a lamp rather than op amps and an LED it’s basically the same with the chorus vibrato switch at the output the vibe should have the wet and dry signal balanced with the two 100K mix resistors R3 and 14 so you shouldn’t need the balance trimmer, voltage divider set up you see on the forum vibe
If vibrato mode is louder or quieter you could use a trimmer wired as a variable resistor in place of R14 to set it to the same level as chorus mode if it’s quieter use a 100K louder use a 250K so you can add or subtract resistance
I’m also not sure if you’ll get any switch pop with the 1u caps
https://musikding.de/docs/web/univibe-ForumVibe-final.pdf
I don’t think it would be straightforward if you’re looking for the same as the original univibe circuit you’d need to add a few components
A vibrato switch would just cut the dry signal out I’d try a DPDT switch in place of R3 that’s the mix resistor for the dry signal I say DPDT but you could use a miniature DPST if you can find one like this
On-Off Mini Toggle Switch DPST — Switch Electronics | Your One Stop Component Shop https://share.google/4cprW0cAW3E3CAeov
It specifies on/on DPDT switches and looks like the switch puts a capacitor in parallel with C1 and C2
So switching C1 to10n will allow more highs then adding the 100n in parallel on the switch will give you 110n close to the stock value
Same with C2 adding from 1 to 10n in parallel will roll off more highs
Now that looks excellent
I like the idea of faceplates they look really good and anything that stops me having to sand an enclosure apply decals etc definitely appeals to me
Check you’ve got a good connection to G2 I’d personally have wired it direct to the DC jack
Remove IC3 from its socket and let us know the voltages on the socket
You’re correct volume 1 goes to ground so a jumper will work
I’ve only got the V1 build document which doesn’t have R11 but I’d guess R11 would be 1K max if for some reason you don’t want your volume to go all the way off
It should work OK with any pnp transistor and your matched set of jfets if the LFO isn’t oscillating that’s your problem I’d check all components in that section
I’ve had solder joints that looked perfect but where dry inside not often but you never know
Does pin 6 voltage still oscillate regardless of the speed pot
It should if pin 2 oscillates
Try reflowing C8 solder joints
I’ve got a phase 90 circuit somewhere I’ll try to find it and confirm voltages etc unfortunately I had to empty my workshop to get some work done to my house recently so hopefully I’ll find it easily enough
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
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
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
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
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
