Debugging Guvernör-Circuit

[redinch]

Hello, i'm having an issue with my Guvernör-circuit.

I assembled it. Plugged it in. In Bypass I have sound. When I hit the switch - silence.

I was able to check the following things:
+ values of components -> seems to be correct
+ orientation of components -> seems to be correct
+ wiring of circuit and switch -> seems to be correct
+ LED -> lights up, wehen bypass is deactivated
+ changed power-suppy -> no changes
+ used battery -> no changes

+ measured voltages follow:
IC1
pin1=0V
pin2=0V
pin3=5V
pin4=0V
pin5=2,5V
pin6=0V
pin7=0V
pin8=10V

After these steps I tried an audio-probe (DIY-Cable like here http://diy-fever.com/misc/audio-probe/ ).
I connected ground to ground at the output-jack, connected my looper to the input-jack und followed the circuit.
The signal seems to travel until R1 and IC pin5. Then just silence remains.
As i measured the resistor (R1), it seems to work.

This is not my first build, but i am fairly new to debugging stompboxes.
Now i have no idea how to act further.   

Schematic: http://diy.musikding.de/wp-content/uplo ... schalt.pdf
Wiring diagram: http://diy.musikding.de/wp-content/uplo ... ovwire.pdf

Pictures of my build:
https://imgur.com/a/3Z05e
https://imgur.com/a/QnIt1

Thanks!

[Keppy]

Welcome to the forum!

For clarification, did you have audio at pin 5 or not? I can't tell from your post if that pin is the last point with audio, or the first point without audio.

Regardless, it looks to me like your IC is completely dead. Both opamps have a higher voltage at the (+) input than the (-) input, which should cause the outputs to go high. You don't have that, you have 0v at both outputs (pins 1 & 7).

It looks like you mounted your IC in a socket. Did you measure voltage on the pins of the IC itself, or on the solder joints on the bottom of the board where the socket sticks through? If those are the voltages on the solder joints or the socket pins instead of the IC pins, then you may have a bad socket connection or solder joint instead of a bad IC. Measure the IC pins themselves to be sure, if you didn't already.

You might also have a short to ground at both opamp outputs. Try checking continuity of pins 1 & 7 to ground with your meter to make sure.

Good luck!

[Kipper4]

Is there a short on ic  pins?

[iainpunk]

Hey, the moment i wanted write an answer the site told me that there was a new post. I read it and i came to the same conclusion and wanted to post about the same. Well,
Viel Glück bei der Lösung Ihres Problems

Iain

[antonis]

As Keppy said, pin 7 SHOULD have some positive voltage, even with Gain pot, R2 & C3 shorted or out of circuit..

2.5V on pin 5 (instead of 4.5V) seems reasonable in case of about 1M5 meter's impedance..

I don't really like your meter's accurance 'cause of that 10V PS reading, but...

[redinch]

Thanks for all quick and clear responses!

I have audio at pin 5 and measured the IC pins themselves.

I had no idea how to check the IC.
Later today I will check continuity of pins 1 & 7 to ground.

(edit: my meter isn't the most accurate one. it displayed about 9.8-10.0V.)

[GibsonGM]

You could carefully remove the IC and check that each pin does not have continuity to the next one.   Don't bend its legs too much and ruin it...go slow in removal and re-insertion.

>If pins 1 & 2 "beep" and show a short, turn the gain pot  well up & check again to be sure it's not set so low as to simulate a short <

It's common to get a blob of solder between IC pins when assembling, called a solder bridge, and the symptoms are just what yours is showing!  You would re-heat with no IC in, and use something to scrape between the pins, such as a razor blade, Xacto knife...until no more short.

Welcome to the forum, you'll get this up and running, no worries...

[duck_arse]

also welcome.

might I ask, cause I can't read it, wot part number IC are you using?

[redinch]

... now i checked the IC. I cant find any shorts. No "beep" between any of the pins (checked solderpoints of socket and direct on the pins).

I turned up gain and volume pots (from 50% to 75%) and measured again:
IC1:
pin1=0.10V
pin2=0.10V
pin3=4.97V
pin4=0.00V
pin5=2.51V
pin6=0.10V
pin7=0.10V
pin8=10.11V

The IC-Part-Number: 74ANLKM - RC4558p

Am i correct with my conclusion, that the problem most likely is on the board itself? Or should I keep on checking wiring of pots and switch?
I will check the whole thing once again...

[GibsonGM]

Are those voltage measurements with the IC taken out? (Sockets only)

Yes, your problem is on the board. Something is not soldered correctly, or the right value parts weren't put in the right place.  Go over all of it again, make sure the resistors are the correct value!       Usually it's user-error that causes this; happens to the best of us.

Maybe you can post a pic of the top and bottom of the board, same orientation so we can see what's up with your solder work?  Might spot something.

[redinch]

No those voltage measurements are with the IC placed in socket.

Without IC i get
IC1
pin1=0.00V
pin2=0.00V
pin3=4.98V
pin4=0.00V
pin5=2.57V
pin6=0.00V
pin7=0.00V
pin8=10.20V

Can this be correct?

[Keppy]

No those voltage measurements are with the IC placed in socket.

Without IC i get
IC1
pin1=0.00V
pin2=0.00V
pin3=4.98V
pin4=0.00V
pin5=2.57V
pin6=0.00V
pin7=0.00V
pin8=10.20V

Can this be correct?

Those are about right for empty socket voltages. They should not be possible with the IC inserted. A working IC can't produce those voltages unless the outputs are shorted (or mostly-shorted) to ground somehow.

[GibsonGM]

Audio probe.  COULD be the switch wiring (which is why I test every circuit before doing the true bypass!).     

A probe will tell you where the signal stops.   Look here:  http://www.diystompboxes.com/pedals/debug.html

Don't forget the cap!  And anywhere there is DC will give a *click* when you touch the probe to it.

[PRR]

The DC voltages are wrong. Little point in audio tracing yet.

The consistent 2.5V on pin 5 is extremely odd. I can't even see a fault which would do that.

[GibsonGM]

Yeah, very true, Paul...it should still WORK like that, tho, shouldn't it?  Perhaps a little distorted.  Which would then put us at pin 5 anyway, lol.   I saw that as perhaps some sort of meter loading issue (?), but it is not correct, as pin 5 should go directly to Vb.

Perhaps the OP would check the path from pin 5 back over to the resistive voltage divider that should provide the 4.5V there?   Should be a straight shot.

[PRR]

Pin 1 and 7, the Outputs, are at 0.10V. This can't be a good working condition. In an extreme case, a BIG signal might bring it out of cut-off with a SPLATT, but I think we need to fix this first.

[redinch]

... sorry for my late response.

i measured every resistor - seems to be fine. unfortunately my multimeter does not measure capacity. so it is hard to check capacitors.

i already did audio-probe. the last point where i get a signal is in front of R1 and pin5 of the IC.

here 2 more pics of my board and bad soldering (hoping you can recognize parts a bit better):
https://imgur.com/a/37oJy

while thinking about how to to debug further, i order a new IC and some other parts. i think i will need them for future projects anyway. 
it's frustrating but also makes a lot of fun to learn.

next i'm going to check the path from pin 5 back again.

thanks again for your kind responses!

[redinch]

... now i am confused. am i measuring correct? i connect black (com) to ground and measure voltages with red on the board.
checking the board, at IN i am not able to measure voltage. at C1 it starts with 2.51V. this makes sense, because C1 is directly connected to pin5.
to rule out C1 i swapped it with one i know it behaves correct. no changes.

[GibsonGM]

Yes Redinch, you should get DC voltage on the right side of C1, because your bias voltage comes in through the 1 Meg resistor there.   

I was looking at a different schematic than you.      Are you writing down your IC voltage just the way it REALLY is?    Because the schematic lists pin 5 where I have Pin 3 (your schematic is using the #2 half of the opamp, and it makes no difference as long as we both know!).

So, if you follow Musikding, you have a problem right away, pin 5 2.57V....it should be nearly 4.5V.   Trace the 1 Meg resistor there back to the "bias network" - the junction of R11/R12 should read about 4.5V.   Please verify this.

You should also read this on pin 3 - and you have noted as much.    If you get pin 5 "working", you may then get signal at pin 7, which is output for opamp #1.        Then perhaps it will be time for an audio probe.    

[Keppy]

So, if you follow Musikding, you have a problem right away, pin 5 2.57V....it should be nearly 4.5V.

That 2.5v just looks like meter loading since the DC impedance there is 1Meg+. A 1Meg meter impedance would reduce the measured voltage by about half. Even if that voltage really is low, though, the output should be going high to drive the (-) input to the same voltage. There's something besides a bias problem here.

... now i am confused. am i measuring correct? i connect black (com) to ground and measure voltages with red on the board.
checking the board, at IN i am not able to measure voltage. at C1 it starts with 2.51V.

That's right. The main point of C1 is to keep the bias voltage of the opamp away from the input. Capacitors do not pass DC, only AC, so you will often measure different voltages on each side.