[Billy]

I’m glad I’m not the only one that missed that +9v silkscreen Stu!

Joking aside you can jumper your LED with a wire to have it on when in effects mode just desolder that leg and solder a jumper wire like this from the leg to the 3PDT lug obviously be careful you don’t damage the LED with too much heat

[Billy]

Good spot sir I was looking at that as well thinking could do with a clean up never even noticed the +9v written all over it

I think you’ve reclaimed the ol’ eagle eyes title

[Billy]

Difficult to see Stu but you may have connected your output jack ground to the ring connection

If you put a jack in like the image below and trace the connections round to thier solder lugs

The ground lug connects directly to the sleeve like this

Your IN jack which I can see is correct, just an FYI if you’re not using a battery you can use mono jacks for both in and out I notice you have stereo for both which are slightly more expensive and welcome to the forum

[Billy]

If you look at the schematic from a join the dots point of view from IN to OUT pads you can see for example if you leave the volume pot out there would be no connection to the OUT pad creating a gap and an open circuit so you need to connect it all up as in the build doc

There are other troubleshooting methods like using your meters continuity check

Without doubt the best troubleshooting method is audio probing where you simply trace your audio through the circuit then come to a point where you get distorted  audio and find your problem area

It’s basically a logical process of illimination

Yes that’s flux most folks use a toothbrush and isopropyl alcohol to remove it

Your build from what we can see looks correct I wouldn’t advise removing anything until we suspect it may be a problem you can dismount your pots they don’t need to be mounted in your test rig just wired to the circuit

Did you get all of your components with the kit I’m assuming you got it from Bruce at Pedalpartsandkits which would tell us your 2n5457s and everything else is good

Also make sure your transistors are securely mounted in their sockets and check you have the correct value pots in the right place particularly your B1M gain pot

I think you should post a picture of where you are now so that we can easily see all your wiring connections

 

 

[Billy]

Looks like Q5 doesn’t need biasing it’s gate voltage should be the same as Q4s drain voltage the 2 pins highlighted in red below

[Billy]

Ah I actually thought you’d probed it when you initially said I can trace the audio back to the output of IC1

Well it was a good exercise  if we learnt something it definitely confused me trying to figure out how you got audio with those voltages etc

Anyway glad you got it going Colin great looking pedal

[Billy]

Alright George that’s all explained in the beginners guide to components on the guides page here

https://guitarpcb.com/forums/topic/pedal-building-guides-mandatory-reading/

The letter is used instead of a decimal point which can often be missed, it’s used mainly for capacitor and resistor values and sometimes for potentiometer values

2K2 for example would be a 2.2 kilo ohm resistor 4N7 a 4.7 nf film capacitor and 2U2 a 2.2 uf electrolytic capacitor

As you can see with the decimal points above it could be easily missed especially on schematics and parts lists

[Billy]

Continuity check all your IN connections to ground make sure nothing’s shorting, there’s no wires touching or shorting on the enclosure

Check that only one side of R20 has continuity to ground

Also check your 3PDT switch continuity in effects mode top row with middle common row

The way you’ve explained your probing you may well have found your problem but with you getting audio initially at IC1 would mean audio was getting into the circuit of course with you testing and moving the circuit it may have developed another fault

Bypass signal just goes from the in jack via the switch to the out jack and not through the circuit so that tells us your jacks are wired correctly but doesn’t tell us your guitar signal is going into the circuit if you don’t get audio on the in T pad then it’s not going into the circuit

*Edit

I tried setting up my probe with audio to the input

It did work on a confirmed working fzzz  bxxx when I probed the IN pad it was a lot louder and fuzzier than the out pad but I did get audio

So there you go Colin weird but it works!

Here’s the link to Tonmanns guide

https://drive.google.com/file/d/1pG8H8lyj9jUDFTqtcJ1QbHNTldIrPnP3/view?usp=sharing

 

[Billy]

Normal set up would be to have your probe connected to out, so ground one side then plug your out cable into your amp and the other end to your probe then it’s just a case of following the audio path with the probe end

Audio in as normal to in jack with whatever you’re using phone, guitar, mp3 etc I use a looper pedal just continually playing a loop, so I’ve got 2 free hands

Obviously making sure it’s in effects mode I’ve done that more than once not switched it on only realising a few head scratches later

With you getting output at IC1 initially that would indicate everything before it was ok

Now that you have correct voltages probe pins 1 and 7 IC1 to see if you get audio

If you think audio goes from in pad straight to ground just continuity check your in pad to ground to check it

At this point I wouldn’t worry about resistance readings the initial resistance readings were just a process of elimination because your VR voltage was 6.5v

So we basically check from VR and up to IC1 to make sure everything’s correct value wise etc for example we can see on the schematic from VR to pin 3 we should have 220K resistance (R19) you can see from pin 1 going back to pin 2 we should have 510K (R16)

So you’re checking everything before you condemn anything in this case IC1 eventually

When I get home I’ll link you to Tonmanns guide on checking op amp circuits

 

 

 

 

[Billy]

I’m slightly confused Colin I thought from your initial post you had audio probed the circuit and were getting audio output at IC1A

Is that the case

 

[Billy]

As long as you have power going to both the main and 3PDT pcbs that’s ok and if, as you’ve said you get 9v readings on the pcb that confirms you’re getting power

When you say the potentiometers are not hooked up do you mean they are not soldered to the pcb? they need to be soldered to the pcb otherwise you’ll have an open circuit

Incidentally for a first kit that looks really good and very well put together I’m assuming you’re not new to electronics?

[Billy]

Thanks Wilkie I’ve  learnt something I was trying to figure out why Colin was getting 66K resistance between pins 6 and 7 using the schematic I thought those 22Ks R12, 13 and 14 aren’t in parallel so why’s it 66K? Paralell connections always throw me

I’ve just looked again and see R13 is actually a 68K in reality, so the 66K is about right

I did read the notes honest!

Colin you can use any dual op amp to test 4558, NE5532 etc doesn’t need to be a TL072 to test it

[Billy]

The feedback loop is between the op amp pins where it goes from output back to an input

E.g. IC1B from pin 7 output back to pin  6 inverted input with R13 and C16 in the loop known as negative feedback this alters gain, filters frequency etc

Your resistance I think would include  R12 and 14,  so 3 x 22K or 66K could be correct we’d need someone with better knowledge than me to confirm it Cybercow or Wilkie or Bruce or Barry or

[Billy]

I don’t see any bridges anywhere

With the IC being an active device I have had occasion in the past where with it out of socket voltages were fine in socket way too high changed the IC no difference and I eventually found a minute solder bridge

Now we know yours is ok until IC1 is in circuit I’d try another TL072 if that doesn’t work then check and visually inspect for solder bridges or shorts under magnification

C18 I think it is, solder joint also looks dull / dry

Another check you can do is with no power to the circuit check resistance between pins 1 and 2 should be around 510K and 6 and 7 around 22K this will let you know the op amp feedback loops don’t have any shorts or open circuits etc the op amp output can affect the inputs so worth checking

Nice to see you too Bruce hope you and yours are all well

[Billy]

That all checks out with R17 and 18 apart from obviously the junction voltage of 6.5

Looking at your solder side I’d reflow C21 joints, if that has no affect

Take voltages on IC1 empty socket

Then with no power to the circuit take resistances from VR to IC1 pins 3 and 5 again you don’t need the IC in

 

[Billy]

You can’t test resistor value in circuit accurately

R17 and 18 voltages should be 9v top side of R17 and 0v bottom of R18 where they join should be half of the power supply 4.5v

Check the bottom end of R18 has continuity with ground touch the resistor leg with your meter probe not the solder joint

Post a nice clear in focus photo of the solder side of the pcb

 

[Billy]

If you haven’t already reflow the solder joints on R17 and 18 just place your iron on the joints for around 4 seconds till it flows nicely

What are your voltages on pins 4 and 8 of IC1

[Author]

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