[Billy]

I can see why G2 was such a pain I meant to do it on the topside of the pcb

There is a chance you could have fried something by inserting IC4 in the wrong way around and powering the circuit

You don’t have VB on IC1 all pins should be around half your power supply except pins 4 ground and 8 power check what voltage you get on the junction of R32 and 33 the voltage divider

[Billy]

You dont need to put it through the hole, ideally yes, but just tin the wire end place it on the G2 pad and melt the solder together for around 3 seconds, remove the IC from it’s socket and just take care and take your time if you put enough solder on the wire with the solder already on the pad it should be fairly easy, unscrew your pots so that you can raise the pcb up a little

If you look at this picture you’ll see I’ve simply tacked the resistor onto the +V pad all I did was tin the resistor with solder hold it on to the +V pad and melt it

[Billy]

I’d just run another ground from the DC jack, a nice short wire

All I’d do is melt the solder and stick another wire in the DC jack ground lug then over to G2 just tin both ends of your wire and you can do it on the topside of the board save you removing it from the enclosure, you could actually just tack both ends on if you tin both ends it’ll just be a case of holding the wire on and melting the solder in place

It’s a beautiful sounding analog chorus you’ll love it I always keep going back to it and ditch the all singing all dancing choruses

[Billy]

You also need to wire G2 top left to ground can’t see if there’s a wire there, it doesn’t look like there is and IC4 looks to be the wrong way around dot needs to go to bottom right so just flip it around, that will be why your voltages are so high for IC4 no ground connection to pin 4

[Billy]

That’s what it’s all about Stu learning

I’ve been building for some time and still learn

I would say to the vendor he may offer something it doesn’t actually say on the listing

As Feedback says it’s not a well known fact that most but not all Russian diodes have the band on the anode + side

you could see enough in your pic to see it matched the silkscreen but as I say when I realised it was a germanium is when I thought is it Russian?

We may have got there sooner if we’d seen the entire thing but it’s good to get in the habit of fault finding in a logical manner, find your fault then check what’s causing it rather than change anything, in your case a reverse biased diode causing less output and having a knock on effect, so it’s a case of finding the cause and checking everything around the fault to hopefully lead you to the problem, you immediately recognised that Q2 and 3 voltages were wrong so you’d then trace it back to see what’s going into them and so on, sounds easy but as you know isn’t always!

 

[Billy]

I thought you had it working with the previous TL074 swap

I’ll have to admit I missed it too and that’s after a few debugs where the 2nd ground not being wired was the problem so how I missed it I’ll never know!

But glad you got it fixed

When you get high readings on op amps and the empty socket like that it’s usually a faulty IC,  bad ground, solder bridge / short, bent IC pin or IC not located properly in it’s socket or dry solder joint

Here’s a link to Tonmanns op amp testing guide

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

For example If you’d have taken a resistance reading from pin 4 to ground you would have got an infinite ohms reading telling you it was open circuit ie no connection, so a very handy guide

 

[Billy]

Ah was it a D9 series Russian diode? they have the band on the anode side

If that wasn’t clear I’d perhaps mention it to the vendor they may not know

Just a shame we couldn’t see the damn thing we’d have got there sooner, but it’s all a good learning experience

We’re always harping on about nice clear pics so we can see everything clearly I suppose this vindicates it but I could see the end didn’t see a band so thought it’s correctly orientated

I actually thought when I realised it was germanium the glass was cracked

[Billy]

What are the voltages on IC3 empty socket

[Billy]

I wouldn’t give up yet Stu

If it works moving the bias control it’s a case of finding out if there is enough voltage going into pins 1 and 16 looking at your Q2 and 3 voltages in comparison to  the working voltages yours are low specifically Q2 B Q3 B,E

So it’s trying to find out why check what voltage you get both sides of D3 and update us with your transistor voltages

[Billy]

Some info here Stu

https://guitarpcb.webs.com/apps/forums/topics/show/13409170

http://revolutiondeux.blogspot.com/2012/07/mad-professor-snow-white-auto-wah.html?m=1

I’m having to work for the first time in 6 months today so no sitting around on my phone doing nothing today for me haha

If the problems not prior to  Q2 and 3 I’d check all components around the transistors bear in mind bias will alter things turn your bias pot all the way down for the least amount of resistance going into IC1 then very gradually increase it pins 1 and 16 of IC1 look low but should now be better so I’d try adjusting bias to see if it improves the wah’ing

Unfortunately I don’t have the voltages for IC1

You’ll get it going just takes a bit of time it’s basically a logical process of elimination where did you get your kit

 

[Billy]

The 4.2v on the other pins is VB half your power supply as it should be

You’ll see all the VB points on the schematic where you’d expect half of the power supply voltage give or take, that tells us your voltage divider R29 and 30 is working and providing the correct bias voltage to IC2B

Did you reflow the solder joints on C8

I wouldn’t change or alter anything unless it’s verified as faulty

[Billy]

Another excellent looking and sounding build Dan

 

[Billy]

Pin 14 at 1.6v is low can’t see R24 and C8 left joint looks like it could be dry

Reflow all your components around IC2D

[Billy]

Stu post all your IC voltages to see if there’s any indication of where the fault lies

Your Q2 E should be the same as Q3 B

Q2 B voltage is too low but the problem may precede it so IC voltages will hopefully point us to where it may be

[Billy]

Mike remove IC1 from its socket and reflow the solder joints  what voltages do you get on pins 2,3,6

[Billy]

Ooft you were fast there Ray

Just got an email notification, thought I’ll answer that before I retire and wham! Wilkie1’s got his speed skates on and I couldn’t even see the chequered flag yet!

[Billy]

Enjoy building it Tony I’ve built lots of different phasers but keep going back to this one

I don’t know your experience but any problems or questions just ask

 

[Author]

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