[Billy]

Well done to you Tom glad you got it working

[Billy]

Yes that’s right Tom

You’ve got the correct voltage going into IC2A but not coming out if you’ve only got 1.4v on pin 1

Try reflowing the socket solder joints with the IC out of socket of course,  if that doesn’t make a difference and you have a spare 4558 try that

[Billy]

You’re correct Tom VB should be half power around 4.5v ish 4.2  at your voltage divider junction is fine what is the voltage on pin 3 of IC2A with the IC in and out of it’s socket

IC2A is being used as a voltage buffer sending the VB bias voltage to your op amps so I’d expect they aren’t biasing correctly

If everything is as expected at the voltage divider junction there’s not a lot between there and the input pin 3 so I’d think it’ll be either the IC isn’t securely snapped into its socket, you’ve got a dry solder joint / poor connection or solder bridge on the IC socket or the socket or IC is faulty

[Billy]

Hi Aryk

The 4558 voltages will be your usual half power 4.5v (VREF) on the input and output pins, 1, 2, 3, 5, 6, 7 then 9v pin 8 and 0v pin 4

Your 4.5v reference voltage coming from the voltage divider junction of R17 and 18

The input and output buffer Q1 and 2 voltages will be the same, around

C 9v

B 3v

E 2.5v

I say around because the voltages depend on what your power supply puts out and you’ll get a wee bit of voltage drop through components

 

Here’s a basic audio path using the tube screaming ultra schematic which is more or less the same

 

Audio Probe PDF just in case you haven’t used one

 

https://drive.google.com/file/d/1T9OsJ0riQhm1QFWPfNQ5q5guikuFKDRN/view?usp=drive_link

 

You can build a basic one like this

 

https://drive.google.com/file/d/1cHA_v6L8wqf9hfEW57xejZZ0EIGFJdzV/view?usp=drive_link

 

Solder one side of a 100n to 1u ceramic or film cap to a mono jack tip lug solder the otherside to a piece of wire then solder something fairly robust, like a piece of paperclip, to the wire end for your probe

Solder another piece of wire to the ground lug with a small croc clip to the wire end

 

[Billy]

I’ve seen a few of your builds over on reddit

I’m liking your relic’d enclosure work lately

I’m u/mcknib on there

 

[Billy]

As you’ll know Ollie

You definitely need pins 4 and 8 for power and ground

Just for future reference as you saw IC pins are usually shown in the power section of the schematic where you’ll see a small V- 4 and V+ 8 indicating dual op amp power pins obviously a small 4 and 7 and 4 and 11 for single and quad op amps

 

[Billy]

Make sure your switch is an spdt on/off/on

It’s sometimes stamped on the metal side part

The switch just selects soft clipping options LED symmetric clipping or silicon diode asymmetric clipping and in the off middle position just the op amp

Noise I’d check all your ground connections are nice and secure

Obviously the source depends on what type of noise it is but I’d always check ground regardless

https://www.premierguitar.com/gear/pedal-troubleshooting-and-maintenance-101-part-3

[Billy]

Do the old wire wiggling check and make sure you’re getting power to the main pcb

Heres an audio probe PDF

https://drive.google.com/file/d/1T9OsJ0riQhm1QFWPfNQ5q5guikuFKDRN/view?usp=drivesdk

You can make a simple one like this

https://drive.google.com/file/d/1L12rjsR49pUTq7CRUhAzEFWz3li_pFvo/view?usp=drivesdk

Just solder one leg of a 100n to 1u film or ceramic capacitor to a mono jack tip then a wire to the other pin and something fairly robust for the probe to the wire end

Another wire to the jack ground with a croc clip to the wire end

 

[Billy]

Do any of the solder joints touch anything they shouldn’t when it’s in the box eg input jack metal parts or one of the 400v cap pins near the pcb edge

Leave it wired in the box and lift the pcb up so it’s clear of potential shorts on any bare metal parts and see if it works

Your bypass works so you know the jacks are wired correctly and it’s only when you switch over to effects mode you’ve got no audio

If everything worked prior to boxing it and your offboard wiring is correct then it must be the solder side shorting to something in the enclosure or the very common and easy to do inserting your in cable to your out jack and visa versa with the enclosure being the wrong way up

You’d still get bypass but no effect

From what I can make out your wiring from pcb in and out to the 3PDT pcb looks correct

 

[Billy]

Check you have your in jack tip blue wire soldered to the correct lug with a jack inserted follow the tip connection round to its solder lug like this

[Billy]

Happy birthday to you Barry boy

Have a splendid time

 

[Billy]

Those voltages all look good, pin 5 is a bit high on the PT2399 but afaik it’s not used

Do you have and know how to use an audio probe

All your component values and orientation that I can see look correct

You get bypass that indicates the jacks and bypass side of the 3PDT are OK

Try reflowing the solder joints on the 3PDT lugs going to the pcb in and out pads reflow on the 3PDT lugs and solder pads they look like they could potentially be dry

Your voltages as I say look good so it’s hopefully just something like a dry solder joint stopping audio getting through the circuit in effects mode

[Billy]

You’d need to post voltages for each pin on the ICs

Like this

PT2399

1. 5v

2. 2.5v

3 0v

4 0v

Etc for all pins of each IC using the pin numbering orientation in Barry’s diagram

If your output for the L78L05 is 4.99v that’s OK

Did you try swapping the PT2399 in case it’s damaged I think with incorrect orientation you may have caused a dead short with ground pins connecting to power

Depending on how long you had it powered this way it may have caused damage

 

 

 

[Billy]

Your PT2399 is the wrong way around notch should be at the bottom

I’m assuming you’ve oriented it that way because the socket notch looks to be at the top too obviously the socket being upside down doesn’t matter

Where did you get your bi colour LED? is it common anode

[Billy]

You can use the MN3007 no problem just follow the instructions in the build doc for the jumper orientation

I’ve built around 8 using the MN3007

 

[Billy]

No, go with that Steve pots have a + or – 20% tolerance so it’ll make little difference if any

20K could be anything from 16 to 24K

25K from 20 to 30K

You can check the resistance across lugs 1 and 3 to find out the exact value of your pot

 

[Billy]

All the components that I can see look to be the correct value and orientation

Do your pots have plastic covers on the back of them

[Author]

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