Help needed trouble shooting IC Based Overdriver circuit

Guitarist335 · July 25, 2020, 11:04:07 AM

Ignore- =duplicate post.Text deleted. My mistake.

Guitarist335 · July 25, 2020, 11:06:44 AM

Thank-you. I will report in as I proceed.

The red wire is magnet wire. It was recommended to me on another electronics forum I am part of (it's another great board with good advice, as in here). I was told that it is durable and thin. It has a coating on it that must be scraped off at the ends, in order for the ends to conduct. That's the only con, as it requires scraping off with a knife or sandpaper. Regular strippers will not work.

Thank-you also for the clarification as to when to connect the battery for the continuity vs. voltage test. Makes sense.

Guitarist335 · July 27, 2020, 08:51:34 AM

Hi folks:

I finally got around to doing some measurement checks. Because I have moved components around to fit a strip baord I am using, it was difficult for me to follow the diagram that was provided.

I have measured the pin readings however by holding the black probe of my multimeter to the negative terminal of the 9v battery and the positive terminal; t the pins. Here are my readngs and i know that Pin 3 is an issue:

Pin1 0
Pin2. 2.0
Pin3. 0
Pin4 0
Pin5 0
Pin6 2.1
Pin7 4.1
Pin8 0

Of course, I am not getting any sound out of it. I assume it has to dowith Pin 3 having a zero reading. I have been looking at this circuit so long, that I can't see it anymore ;-)

Any suggestions on how I can zoom in on what might be causing Pin3 to have a zero reading?

Thank-you

11-90-an · July 27, 2020, 08:53:31 AM

Can you post also voltage readings of VB?

I am very surprised about pin 7... it should be about 9v... is your battery still "full" (i.e. ~9v)

Before trying to swap the ic, try swapping the battery...

duck_arse · July 27, 2020, 10:43:04 AM

it looks like pin 6 is following pin 2, and is low because pin 3 is shorted to something. but, looking back on your voltages and measure method, I wonder if you have sleeve and tip mixed on one of your jacks.

as we always say ....... PHOTOS - of everything, please.

Guitarist335 · July 27, 2020, 11:18:41 AM

Hi: will get back to you with the answers to your questions. I am using a 9 v battery and I also tried it with a power supply, so i doubt it is a voltage issue.

I have attached two pics. i usuallky don't because I move things around, so it does not necessarily follow the wiring diagram on the site.

Guitarist335 · July 27, 2020, 11:31:57 AM

Reading @ VB is. 8.92

Guitarist335 · July 27, 2020, 11:57:28 AM

This is disheartening. I am close to giving up and starting again.

I noticed that Pin 3 went to R2 before connecting to R.

So I ran a wire from Pin3 to R3. Made no difference.

Guys- don't sweat it. i think I am going to start over.

I used a strip board this time, but I was guided by the wiring diagram in the tutorial. i now realize that it would be better for me to work from the schematic itself. I'll report in once I am getting there. Thank-you for your patience.

antonis · July 27, 2020, 02:21:34 PM

Take in mind some rules of thumb, like only populate horizontal or vertical items and also make same direction wire connections..

(I know twisting 2-3 items legs is a bait to disentangle yourself from discrete joints but get used of not implementing it..)

Guitarist335 · July 27, 2020, 04:30:01 PM

Thanks for the advice. I just rebuilt the entire circuit, with the exception of attaching the jacks and the Volume and Gain pots. I plan to do this is a separate session, as I find that when i get to this point, I get excited about finishing the project- which can lead to mistakes. So, I wil do that phase once I am rested and my eyesight is back ;-)

In terms of the jacks, I have the tips wired with purple and with orange wires. I have the sleeves wired both with white wires. I tested them with a multimeter continuity tester, and they are wired correctly.

I found it a lot easier working from the schematic, rather than the wiring diagram.

Thanks again for looking in on me. Will report in once I have done the rest.

Guitarist335 · July 27, 2020, 11:46:49 PM

Ok..so here's where I am at. I rebuilt the entire circuit, using the schematic.

I have attached three pictures. One is the front of the circuit, the other is the underside and the third is the compartment where I have my pots and jacks.

The circuit is not working ;-( I even used a brand new op amp.

Here are my meassurement at the pins:

Pin1. .0053
Pin2. .0076
Pin3. 4.2
Pin4. 0
Pin5. .0003
Pin6. 8.3
Pin7. 8.9
Pin8. 0

Does anyone have any idea why it is not working. Pin 2 seems like a very low reading. The only substitution I had tio make is that i did not have a 25pF capacitor for C3, so i used a 27Pf.

Thanks for your time and expertise.

BTW- on the middle two horizontal rows on the underside of the circuit board. you will notice that one of those rails has a black marker mark on it, toward the right hand side. That signifies that that particular row is the ground rail. The other row is the + rail.

duck_arse · July 28, 2020, 10:52:01 AM

what is the metered value of this resistor? where is it on the circuit diagram?

Guitarist335 · July 28, 2020, 11:06:02 AM

It i 181 Kohms

It is R1. In the description, he says that it is not even needed. I did not have a 2.2M resistor, so I used the one I had, which is 181Kohms, which i assume is 1.8M?

I thought that since it is really not even needed, the 1.8 could suffice as a replacement for the 2.2M.

duck_arse · July 28, 2020, 11:33:10 AM

180k = 180,000
2M2 = 2,200,000

M = 10^6
k = 10^3

Guitarist335 · July 28, 2020, 02:26:28 PM

I believe that resistor is not necessary, so hopefully it is not causing the issue. Any ideas why this may noit be working? Is there a reading thats out?

antonis · July 28, 2020, 02:36:42 PM

Quote from: Guitarist335 on July 28, 2020, 11:06:02 AM
I thought that since it is really not even needed, the 1.8 could suffice as a replacement for the 2.2M.

When an item isn't necessary, we omit it..

(and not use another item of any arbitrary value..)
2M2 resistor is an anti-pop pull-down item but also sets part of input impedance, which impedance is 2M2//470k bias resistor (R3)..
(you now have lowered input impedance down to 180k//470k..)

Of course, this isn't the cause of not working circuit..

I'd suggest you the use of bare copper wires for connecting items on solder side of board 'cause some of your connections might not form solder joint..

Guitarist335 · July 28, 2020, 03:09:34 PM

They are insulated magnetic wires but I will check them

antonis · July 28, 2020, 03:19:08 PM

Quote from: Guitarist335 on July 28, 2020, 03:09:34 PM
They are insulated magnetic wires

Maybe that's exactly the problem..

Guitarist335 · July 28, 2020, 07:12:02 PM

That may be the reason why a lot of my circuits fail. Magnet wire was recommended to me,. I know the pics are decieving as it looks like the coat in on the ends of the wire, but the other side is stripped bare.

However, now that you have mentioned it, it does not seem like an ideal thing to use.

Does anyone have a recommendation as to what kind of wire I should use to make connections on these boards?

11-90-an · July 28, 2020, 07:46:22 PM

Old toy wire.. Bare copper wire... you can actually use any wire though...

Maybe next time just strip the insulation FARTHER than you would expect you need it. Semms to help for me..

The 2M2 resistor could be replaced with at least a 1M resistor. It's not good practice to go lower than that...

I recommend you read this thread to give you some hope, insights, laughs, etc...

https://www.diystompboxes.com/smfforum/index.php?topic=125004.0

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Help needed trouble shooting IC Based Overdriver circuit