IC Big Muff vero build. Passes signal but no fuzz?

[Bandwagonesque]

 Hi everyone and hope all is safe and well. I wired up an op amp big muff clone this afternoon based off mike livesleys Vero layout. I wired it up and it bypasses signal fine, but when turned on I get only a clean signal with no fuzz if just a very very sparse farty sound with low headroom. All the controls work and react but its just a clean signal being affected. I went ahead and looked at and crossed off the usual suspects: grounding and grounds, trace cuts and jumpers in there right places, solder bridges or cold joints, polarity of diodes and caps, values of all components and pots. I went ahead and replaced the IC's which did nothing and then did the same with the diode set. That sounded the same whether the diodes where in play or out. I then took the voltages from my original op amp muff and then the ones from this Vero muff giving me trouble. It appears on the 4558 chip of my build, terminals 6 and 7 differ in voltage greatly from what's seen in the originals voltages in its 4558. Terminal 8 in my build seems o go all over the place as well. Below are the values of each listed.
      I'm still rather green and not sure where to go from here. I would assume to just start replacing what is coming from terminals 6 and 7 of that chip but want to know if I'm overlooking a more beneficial option to troubleshoot what's wrong around there. I'm also enclosing a copy of mikes layout (please forgive the watermark, i cant get rid of it.) Thanks for any help that can be offered in getting it humming.



IC1.  4558

1. 4.62             8. 9.30
2. 4.69             7. 8.73
3. 4.64             6. 8.45
4. 0.00             5. all over the place. (when I place the probes on this point, the noise in my amp               goes away and the voltage sits at 4.11, then the noise creeps back in audibly             and the voltage appears to take a real dip from there. can someone tell me             whats going on?)

IC2. 741

1. 0.00               8. 0.00
2. 5.02               7. 9.30
3. 4.80               6. 5.03
4. 0.00               5. 0.00



4558 OG OP AMP MUFF

1. 4.62               8. 9.29
2. 4.64               7. 4.63
3. 4.59               6. 4.63
4. 0.00               5. 4.61



741 OG OP AMP MUFF

1. 0.00               8. 0.00
2. 4.98               7. 9.28
3. 4.75               6. 4.99
4. 0.00               5. 0.00

[antonis]

Check resistance between IC1 pin 1 & pin 5)..
You should measure 57k..

[Bandwagonesque]

hi antonis and thanks for your reply. just measured IC1/4558 between pins 1 and 5 and i'm not getting any reading. just to be sure i have my meter set at 200K resistance and putting the probes to the 1st and 5th pins. but still not getting any readings. if it helps at all, im measuring 2.50 volts between the pins 1 and 5.

edit: yeah somethings up, just measured my og big muff at 59K across those pins so its not user error in measuring. hmmm...

[garcho]

Terminal 8 in my build seems o go all over the place

That's a clue, since that pin is the VCC, the positive power input. Ideally it's rock solid and never budges. Realistically it budges, but not anything like what you're describing.

Something is very wrong with the right side's op amp on your 4558, pins 5, 6 and 7 (and the power pin 8 ). Your output is basically hard clipping right at the top of the positive rail. With no signal, that should be at VCC/2, like it is on the working one. Generally, for single sided power supplies in guitar pedals, the inputs and outputs of op amps used in the signal chain should all be around VCC/2. It is a very loose guideline but it can help when troubleshooting. Watch a "how do op amps work" video, and the voltages will seem a lot less mysterious. Perhaps there is something wrong with the voltage bias for your non inverting input, e.g. pin 5.

[Bandwagonesque]

im gonna have a friend drop off some fresh 4558's. this build took up my last one and i'm hope replacing them with some from a differing source will get it working again. garcho, do you think the problem is isolated to the chip itself or one of the components coming from pin 5 or around it? thanks for your help btw.

[antonis]

Just to make things clear..

Did you perform resistance measurement with power off and IC out of socket..??

[Bandwagonesque]

naww i tested it in circuit with the power on. i did the same with my OG muff. am I supposed to measure it out of the circuit completely with no power running through it?

[garcho]

Ohmmeters measure for resistance with voltage, so if you apply external power to what you're measuring, you'll throw the device off. Don't ever measure anything for resistance when there's power present.

[antonis]

So, before you accuse your 4558 for infidelity, make sure its pin 5 is properly biased from pin 1..

[Bandwagonesque]

hi guys and thanks for your replys. I learned something in not powering the circuit while measuring resistance so thanks for bringing that up. thing is, even without power im not getting any resistance across pins 1 through 5. unfortunately my friend misheard me and brought a 7660 ic by instead so i couldn't see if that was the issue either. im assuming since its not measuring simple resistance that its a problematic IC. is that safe to assume?

[Slowpoke101]

If you could upload some clear pictures of both the component and solder sides of your board, we would find it very helpful. And from past experience I've learnt to ask for a picture of your multimeter too - helps to work out if user error is causing confusion.

R5 and R6 are connected in series between IC1 pins 1 and 5. Their total series resistance is 57K, so if you measure across pins 1 and 5 you should see a resistance measurement of about 30K (measurements of resistance with components still in-circuit is usually less than the marked resistances ). Power should not be applied during resistance (or continuity ) tests.

[antonis]

What Ian tells you (much better than my previous attempt.. ) is that pins 1 & 5 MUST be connected via some kohms resistance..

The above connection has dual purpose..
1. DC bias pin 5 (+4.5V coming out of pin 1..)
2. Passes signal from pin 1 to pin 5..

[Bandwagonesque]

Hi folks, sorry for taking awhile to get a reply back. Alrighty so just that im sure, this is how i'm reading the pinout of my 4558 per their datasheets. measuring it with no power connected but with the chip in the circuit, I get no jump on my meter with the meter set at '200K'. I measured both the points as directed by slowpoke and measuring the pins directly. here is a pic of my meter as theres definitely room this could be user error.

1|---u---|8
2|          |7
3|          |6
4|------- |5

also posting some circuit shots of the topology and bottom half. i made an order for some 4558's as i can assume somethings really wrong with that chip if im not getting a reading.

[garcho]

i can assume somethings really wrong with that chip if im not getting a reading

There are 47kΩ and 10kΩ resistors between the points you are measuring, with or without the 4558.

It's hard to judge from the photos but it seems like some of the leads are still copper colored, meaning they haven't been tinned, or taken on the solder. You can see them pop out of the silver solder. There might not be true connection in those joints.

[Slowpoke101]

Have a good close look at the following image;



Pin 5 of the IC socket used for the 4558 does not seem to have any solder...At all.

[Bandwagonesque]

you guys are amazing. I cannot believe i didn't catch that while delousing the whole thing. thank you slowpoke, this case is closed. This thing rips!!! Will have to add this one to my personal troubleshooting journal. 'do not space on soldering EVERYTHING!!!'

[Slowpoke101]

It's always good when you get stuff to work and it's great to help others to get their builds to work 
Garcho gave me the clue from your photos. Good pictures of the board really help.

Enjoy your new toy. I've got one of these OP-Amp big muff clones somewhere which never made it into an enclosure....I suppose I should start boxing some at least. Only have about 30 (or so ) boards that should get boxed up....I'll get there eventually.

[PRR]

> my personal troubleshooting journal. 'do not space on soldering EVERYTHING!!!'

That may rank #3 on the list of Top Ten reasons for no-work.