[Billy]

Here’s V3 build doc

https://drive.google.com/file/d/1WqKQNCBHqxn6tkN-b-mtZ7fskTb68koH/view?usp=drivesdk

Idk if increasing R6 may solve it yours looks like 100R instead of 220R did you try it with battery only power or to try and find the cause try tapping your finger on and off the solder joints to see if it affects the oscillation

[Billy]

What particular circuit of the 3 do you want to run at 18v I’m assuming you’re using 3 separate pcbs do they all have a bipolar supply using a charge pump

A 7660S maximum input voltage depending on what datasheet you look at is between 10 and 12v a pin compatible LT1054 up to 15v so plugging 18v straight in isn’t an option you’d need a charge pump with a suitable voltage rating to do that

As Jeff24 says it’s already 18v with the + rail +9v and negative -9v so rail to rail 18v on ICs 1,2 and 3 of the mule and +18v and minus 9v on IC2 of the kicker 27v rail to rail so there are differences with those 2 circuits

[Billy]

I think if you’re going to use the 7660S you’d need to add a cap and 2 diodes to turn it into a voltage doubler as well as a voltage converter the same as the mule kicker combo circuit

Obviously you’d need to ensure everything is rated for 18v particularly electrolytics if it were me I’d leave the 7660S part of the circuit empty and build it on a piece of vero and connect it appropriately

It’s do-able but not without a fair bit of work

You could cut traces and add your extra components but to me the benefit wouldn’t be massive running it at 18v even with a 9v input you’re probably going to get closer to 16v with the voltage drop through components like the 2 diodes

It’s not simple because you need -9v for ground that part is already taken care of you just need to double the 7660S output voltage

 

 

 

[Billy]

Sorry been working so not had a look for a while

I’ve had a quick glance at your pcb particularly orientation of polarized components which all look correct

Just to clear up some basics do you get no sound at all or no effect but bypass sound

Without powering the board use your meter diode test to check D5 you should obviously only get a forward voltage reading in one direction and OL or 1 in the other then power the board and check if you still get voltage on D5 cathode check voltages on IC6 pins and pin 1 of the BTDR3

You’re basically trying to work out how far power gets to in the circuit  and hopefully narrow down your problem area

You don’t really want to change or replace anything without reason or it will get confusing

 

[Billy]

Post an image of the populated pcb it’s very easy to miss something even after multiple checks

The scratch as said doesn’t look too deep and that part of the circuit just looks like a low pass shelving filter to dump higher frequencies to ground

Lug 2 as you can see connects to ground and looking at the pcb image there’s no traces above the pot the 9v rail runs below it

[Billy]

Just for info most trimpots used in guitar effects are linear B taper you can get log A taper but they’re more for specialist use

[Billy]

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

 

[Billy]

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

[Billy]

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

 

[Billy]

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

 

 

 

 

[Billy]

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

[Billy]

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

 

 

 

[Billy]

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

[Billy]

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

 

[Billy]

I haven’t checked them all but most should be here

https://www.yumpu.com/en/guitarpcb.com

 

[Billy]

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

 

[Billy]

Those look like pnp transistors not jfets

[Author]

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