Help needed trouble shooting IC Based Overdriver circuit

[Guitarist335]

Hi:

I wonder if I can get some advice on this. I carefully built this project:

https://www.diystompboxes.com/smfforum/index.php?action=post;board=2.0

Because I failed a few times, I took my time and made sure that every connection is correct and soldered on a PCB - at least, so i thought.

Despite my efforts, it is not working. in fact, no sound comes out at all.

I did an initial pass at trouble shooting by using a continuity tester and ensuring that my connections are actually connecting, and that there are no shorts. I did not find any.

Next, i would like to test voltages at the IC pins. But because I am fairly new to this, and am not that versed in using a multimeter, I need to understand where to put my multi meter probes and what voltages to expect.

For example, if I put the positive probe of the multimeter on Pin 2 of the IC, where do i out the negative probe and what reading should I expect? If someone can help me to this type of testing, i'd be very grateful. I'd really like to learn how to do it.

Thank-you for your time.

[GibsonGM]

Hi Guitarist, welcome...you will make this work, don't worry

The link you provided doesn't take me to the schematic of what you built.  Maybe you can re-post that...

- is the circuit 'complete', meaning it has the in/out jack and footswitch attached?  There are often errors in wiring at the switch that can make a working circuit seem like it's malfunctioning.

- you're sure the battery is not dead? (it happens)

- to read voltages with the meter, set it to "DC volts", and connect the black probe to the battery "-".  This can be at any point...the battery itself, where it attaches to the PCB...as long as it is a DIRECT connection to the minus.  Using a jumper wire for this is useful, it frees up a hand.

You then take voltage readings using the red probe.  Be careful not to short the IC pins together!  Keep a steady hand, measure, remove, and note the voltage.

The IC has a notch at the top end.  From there, you count the pins on the LEFT side "1 2 3 4" down, then across to the right, and go up "5 6 7 8".

This should get you started.   And don't forget to measure and post battery voltage first

>> don't try to make voltage measurements if the meter is set to continuity or resistance ("ohms"), it can damage it/blow a fuse.

[Guitarist335]

GibsonGM:

Thank-you. My apologies. i linked to the wrong page. this is what i am working on. It is found on this very site:
 
https://www.diystompboxes.com/projects/intro.html

Thank you for your patience helping a newbie. Yes, I hooked up an in and out jack. I have not installed a switch- am i supposed to?

I will report back what measurements I am getting once I have had a chance to take them.

I am sure I am doing something stupid that is preventing this from working, because I was very careful connecting the components.

[11-90-an]

Pictures? 

To use a multimeter, connect the BLACK probe anywhere to ground, and place the RED probe on where you want to get a reading. (Make sure to turn the multimeter on first... ) After that, take note of all the voltages you get and write them down and post them. Read this for reference... https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

The switch is up to you... I think we should check your circuit first before installing one...

[Guitarist335]

Hi:

I hooked up the multimeter and did the following:

I connected the black probe to the negative terminal of the 9 V battery

I think ran the postive lead to each of the pins. The following are my readings (please note, when i had the multimeter on the V Hz setting, the readings were all over the map and too minuscule to land ona reading. When I switched the multimeter to mV Hz< I got the following readings:

Pin 1.  2.22
Pin2.   8.1
Pin3.   104
Pin4.   2.2
Pin5.  2.198
Pin6   2.7
Pin7   3.9
Pin8.  0

This is the meter I am using:  https://www.amazon.ca/gp/product/B0837LPBTD/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1


On my IC Chip, the following is written on it:

J19A006M
UA741CP

This is it:  https://www.amazon.ca/gp/product/B07LFSV98Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


Am I doing something wrong?

Thank-you for your help. I can try to get a photo done tomorrow.

P.S. I am using a brand new Duracell 9V battery

[11-90-an]

Now i don't know technicalities but i am sure that pin 4 should be 0v and pin 7 should be about 8.7-9...

Pictures would really be helpful...

[willienillie]

Here's the pinout for a 741, and many other 8-pin single opamps.



Note that this is the view from the top, where the markings are.  Also note that the pins are numbered counter-clockwise around the chip.  Some chips will have a notch between pins 1 and 8, some will have a circular indentation next to pin 1, some will have both.  But it's just to let you know where pin 1 is, and thus the rest.

We generally don't use the Offset Null pins, so they will be "NC" for us, like pin 8 (No Connection).  See in the schematic you linked that there is nothing connected to pins 1, 5, and 8.

Hope that makes sense.

Now, about that 104 volts on pin 3... 

[antonis]

You may notice "dual" mesurements (like on VA & VB) points are overkill but, trust me, they aren't..

[duck_arse]

on your meter, you want the V~- range, not the mV~- range. when you do Antonis's continuity measures, ensure the power to your built circuit is off/disconnected. using the resistance range will give you "numbers", using the continuity/buzzer range will give you "yes-ish/no-ish" results.

we always really really really like to see photos of the built, because if it is as simple a matter as a misconnected jack socket, or bad pot wirings, it saves everyone concerned much aggro.

[Guitarist335]

I am sorry but I took my measurements before I read the latest post, which came in after i measured. Thus, i was measuring with the battery connected. i posted these measurements but I suppose they are not correct. Maybe that's why my multimeter was acting strange?

Anyway, i posted the measurements and a picture or two. i hesitated about the picture because I had to move components around, to use the PCB wisely, and so i am not sure if the pics will help you. they are difficult to follow, even by me, and I'm here ;-). Outside of the pic, I have a unit I built whihc houses the volume pot and jacks/gain.

Anyway...I need to go out but I will do the measurements over later abd post them. If anyone has any advice in the interim, i am open to it.

'Thank-you

[antonis]

Don't get me wrong but this very board is an ideal example for "What to NOT do"..

That's the reason for ignoring the whole of measurements..

[antonis]

I should suggest you to uitilize one of following boards as a start..

[Guitarist335]

Hi Antonis

As I mentioned, I am a newbie.

I think I will take your advice and order some of those boards before I try this again.

[Guitarist335]

I just ordered these two products and they should be here tomorrow:

https://www.amazon.ca/gp/product/B07ZNZVDL6/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

https://www.amazon.ca/gp/product/B081YGHS73/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I plan to rebuild this and breadboard it first- although that gets a little messy.

if you folks are willing, perhaps i can post updates along the way and you can help me make sure I'm not screwing up.

Thanks!


I also built the attached board (see pic) to help with breadboarding and pots/jacks

[antonis]

I plan to rebuild this and breadboard it first- although that gets a little messy.

If you are a little careful on breadboarding you'll be able to "copy - paste" the circuit on protoboard..
(e.g. as little flying jumpers as possible, supply rails kept on the same side, no cross over items etc..)

[Guitarist335]

The instructions are very specific, so I suppose I can follow them on the strip board as well

[Guitarist335]

Update:

I bread boarded the circuit and have been successful. I have not yet installed the diodes yet, but without them, it works and I can hear the distortion. I will report back once I do the rest tomorrow,.

[11-90-an]

Nice...

Don't worry, you will get to have your first pedal working in no time...

[Guitarist335]

Thanks for the encouragement and help.

[duck_arse]

ahh, to clarify my last post, in case my ciders are cut off -

when you do voltage measures, you need the battery or external supply connected and on.
when doing resistance or continuity measures, you need the battery or supply disconnected from the circuit.

and, now you have it working on the breadboard, measure the voltages around the IC pins, and we'll mark your homework.

may I enquire - what is that reddish wire that looks like string on your perfboard?