[Billy]

What’s your voltage both sides of R1 and did you test each board before installing into the enclosure

Your voltages all look too low but it appears with the fluctuating voltages the LFO is working all pins apart from 4 ground and 8 power on IC1 should be around half power your voltage divider resistors R32 and 33 look the correct 56K value so checking R1 voltages will let us know if you’re getting VB (bias voltage/ half power) to IC1

Its difficult to see R1 – 220K which should be red red black orange brown your 4th band looks grey which is 2M2? Could just be the reflection but that would definitely account for your low voltages

Easy enough to check resistance along that path without desoldering anything, with no power to the circuit take a resistance reading from VB the right side of R1 to IC1 pin 3 should read around 221K

 

[Billy]

Could be several possibilities Paul but it sounds like you have no modulation

Did you adjust the trimmer to find the sweet spot

Is it a kit there was a spate of kits containing incorrect values

One of the most common errors is not wiring ground to the G2 pad top left of the pcb and also not placing the jumpers correctly for the BBD IC2

But as I say there are other possibilities

When you post your pictures make sure all components can be seen clearly and post images of both sides of the pcb and all offboard wiring to jacks DC jack 3PDT etc so that it can be traced

 

[Billy]

And then there’s these you definitely need to be slightly mad to attempt an SMD build don’t know how many components I’ve lost blowing them right off with my hot air gun before I thought maybe I should turn it down a bit

And no it didn’t fire up right away it seems even with modern stuff the old dry joint stops technology in it’s tracks

[Billy]

Haha Carlo

I definitely never said my wiring was neat

Passable maybe! your men for really neat, tidy wiring jobs are Cybercow and Playsforfun I think Barry linked his combo build PDF,  now that’s neat!

 

 

[Billy]

I’ve rarely come across any PCB supplier that provides holes for standoffs these days even those with no onboard pots or switches because as you know most pcbs have layers and via traces etc so putting a fairly large standoff hole in it just means more layout work and a larger pcb

I personally don’t use them and have never had to with the many gpcb circuits I’ve built

I tend to keep my wiring very short and to avoid anything shorting on the enclosure I line it with kids craft foam and have never had a problem I also never use solid core wire

I wouldn’t advise drilling it with the potential for cracks etc

I’ve built this circuit and the 3 wired pots held it in place securely no problem they barely move if your wiring is nice and short

Obviously everyone has their own preference I rarely use onboard pots I like to wire them in to give me a little flexibility on pot placement

This is the foam I use

https://www.ebay.co.uk/itm/282978430287

I’ve built and sold in excess of 500 pedals and never had any problems or returns using this method

 

 

 

[Billy]

I thought you were gonna say it’s in a 1590A for a minute

Looks pretty tidy to me Chuck very nice indeed

[Billy]

Nice one Cybercow that’s a real clean looking beast

[Billy]

That is a very nice build looks really good even the LED looks like a distant planet

I absolutely love the mini me and will definitely be stealing some ideas for my next one, you make it sound and look awesome

[Billy]

Another good looking build you’ve got there I might just give it a go!

[Billy]

Nice looking build and a good idea excellent

[Billy]

How did you know my middle name was Brutus? You’re a man of many talents Ray Julius

[Billy]

Haha I’ve skimmed on more than 1 occasion

Must be coming up to 500 pedals built, started audio probing one that worked then didn’t the other night only to eventually find I’d put my in cable to out and out to in on my test box

If that doesn’t take the prize for an apparently ‘experienced’ builder I don’t know what does!

 

[Billy]

Rusty

S4,5 and 6 aren’t used with the 3PDT board just ignore them and the main pcb LED and CLR and put your LED and CLR on the 3PDT board

The MA pad is for the Micro Amp and you can ignore that too detailed if you scroll down in the build doc for the original placement of R3

Enjoy your build

[Billy]

Yes you would just use the same value Bruce

It looks from the v1 silkscreen that you could use either electrolytic or film caps

You can use film or MLCC capacitors just remember  film types can get pretty big over 100v voltage rating

[Billy]

It’s no problem Johhny that’s what we’re here for, glad you got it working it’s my favourite chorus

It’s not an obvious problem at all, we all do it regardless of experience and sometimes we don’t see it no matter how many times we look

You will find that the 3 things I mentioned are frequently the cause of non working builds so that’s why I mentioned it, if any of mine don’t work I’ll check the wiring first then do a visual check of both sides of the pcb to make sure all the values and orientation are correct and there’s no dry solder joints or solder bridges

Next thing I do is check power in as you did and all other voltages you’ll see reference voltage flags on the schematic VB, 9V etc so you can check voltage at those points

If you look at the power section of the schematic bottom right you’ll see 9v going in through your 47 ohm resistor along to some filter caps C13 and 14 then you’ll see IC1 and 4 pins 8 to v+ and 4 to v- telling you you should get v+ on both pin 8s around 9v and ground 0 volts on pin 4s

From there it goes along to a voltage divider R32 and 33 both the same value which would half exactly your +9v giving you your VB voltage bias of around 4.5v so you’d then know what you should get on anything marked VB

So you were on the right track recognising there was a problem at R31 all you would do then is check everything around that part of the circuit and trace it back hopefully finding you’re problem

 

 

 

[Billy]

Welcome to the forum Johhny

At a quick glance your R31 is a 47K ohm resistor should be 47 ohm so 47000 instead of 47

The colour bandings for a metal film 47 ohm 5 band resistor should be yellow purple black black brown or yellow purple black gold brown

That would stop you getting full voltage it being a wee bit larger

Your IC4 also appears to be the wrong way round your notch should be at the bottom

The most common problems in debugging are quite often incorrect component  values and orientation or dry solder joints, not always but usually

I’d advise checking all component values and orientation to the build doc

Use Barry’s handy resistor and capacitor chart here

The GUIDES PAGE – Mandatory Reading for all!

Or a calculator like this

https://samstechlib.com/610938/en/

I’m at work so haven’t checked in detail but as I said at a glance and from your information I quickly noticed these 2 problems

 

[Billy]

You don’t need to be that precise for pedal circuits as you know most components have a tolerance

Caps especially have a fairly large tolerance + or – 20% and greater if a pedal requires matched or close values it’ll usually tell you in the build doc

If you get your components from a good supplier then they should be fine

You should still make sure your values are correct before installing them using your meter we’re all human and even top suppliers can make mistakes with labelling etc

 

 

[Author]

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