DOD 250 yjm spec

[Kipper4]

This ones been on the bench a couple of days now being debugged and i cant figure it out.
Heres my rant cause its bugging me now.
I had it passing audio earlier but
its not distorting at all and the volumes way to low.
I tried differant op amp LM833 and tl072.
Every now and then when i got frustrated and strummed the guitar hard it was like a bit louder (more like the loudness i expected) but only for a tiny second then back to ususal.
Dont get me wrong just getting it to pass audio is a triumph for a newbie like me.
Somethings must be right. But something is glaringly obvious WRONG.
Ive been over it with the meter. replaced a few bits even, rerun some joints.
Anyway someone heres bound to have built this so heres the schematic i'm working from

http://www.diystompboxes.com/smfforum/index.php?topic=97133.0

Any suggestion or guidance gladly accepted and appreciated.

[J0K3RX]

What layout did you use? Any pics?

[PRR]

> only for a tiny second then back to ususal.

Bad contact. Bad jack, bad solder joint.

[Kipper4]

I'm gonna have another go asap. It was one of the above last time.
Probably same this time thanks Prr.
Joker i would post a pic but i dont have online album or storage sorry.
Pm me your email if you like
thanks

[Tony Forestiere]

Dropbox is great for file sharing from anywhere on the web: http://db.tt/PaT3BRtB
Check it out.

[Kipper4]

Thanks Tony
I managed to get it to work this time. The last time you shared the link it just kept crashing.
I now have drop box.
Is it possible to upload mp3 in drop box too? please.
Is that a French name Tony?

[Mark Hammer]

Type of chip will not make the difference between clipping or not, although obviously a bad/fried chip of any type certainly can.

Before you rip anything else apart, confirm for yourself that the stompswitch is behaving as it should.

[Tony Forestiere]

Thanks Tony
I managed to get it to work this time. The last time you shared the link it just kept crashing.
I now have drop box.
Is it possible to upload mp3 in drop box too? please.

1) Yes, you can share MP3s from your Public folder. Upload them and create a Public Link. Post the link.
2) Now go to the "What to do if it doesn't work" sticky and post info and pictures.
3)

Is that a French name Tony?

Yes, sort of. Short story. During the Norman Conquest of 1067, several Dukes De (La) Forestiere pledged fealty under Tancrid the Great. My forebears settled into the Sicilian port cities of Messina and Palermo, and my married Grandparents immigrated from there to the US at ages 16 and 20. I am a WOP with a FROG last name. No offense to anyone. Just poking fun at myself. 

Kipper: Do step 2

[Kipper4]

1.Name of the project: DOD 250 yjm 308 preamp overdrive
2.Links to the source of the project web site with the schematic or project, layout and wiring diagram. Link in first post to schematic
3.Some candid admissions about how closely you followed the suggested layout, if any. If you just perfboarded it, say that, and if you can, include a picture of the board.
https://www.dropbox.com/sh/7ma9n53c5jqdgsr/d-0TvwYXDL?m


4.Any parts substitutions or modifications you made to the original. differant op amp using LM833N

5.Whether or not it's a positive ground circuit like a PNP fuzz or a Rangemaster that has been hacked to work with negative ground. This is a special case, but a common one. "Positive ground" means that the positive/red lead of the battery clip is connected to signal ground. "Negative ground" means that the negative/black lead of the battery clip is connected to signal ground when the effect is operating.

this is a negative ground curcuit


6.What it does and does not do how it works; partially or not at all. For instance, if it lets no sound through; or if it makes a harsh, distorted sound only when you strum hard on the strings at full volume; or if everything is really, really low volume.

at this moment the out put is not overdriven at all and signal strength is only just there.

I hope i did this right and i hope the drop box link works

[Tony Forestiere]

C'mon man, voltages. 

[Kipper4]

voltages?
Where mate?

[Kipper4]

battery 8.3

IC
pin 1  6.77
2       6.77
3       7.25
4       8.27
5       0.29
6       8.27
7       0.253
8       0.412


i'm guessing thats what you mean man.

[Kipper4]

oops might have got that wrong i've read that bit now in the debugging
heres goes this time black to earth

battery 8.2
Pin
1=1.482
2=1.482
3=0.964
4=0
5=6.79
6=0
7=6.8
8=7.76

[Mark Hammer]

Is that a French name Tony?

Yes, sort of. Short story. During the Norman Conquest of 1067, several Dukes De (La) Forestiere pledged fealty under Tancrid the Great. My forebears settled into the Sicilian port cities of Messina and Palermo, and my married Grandparents immigrated from there to the US at ages 16 and 20. I am a WOP with a FROG last name. No offense to anyone. Just poking fun at myself. 

Not sure if you are a fan of the Montreal-based cooking/comedy show Bitchin' Kitchen, but we're huge fans here in our house.  In follow-up to a tongue in cheek travelogue through "beautiful downtown St. Leonard" that they had on the show (the host, Nadia Giosia is from there), I stumbled onto this site - http://www.italiandictionary.ca/ - which is the "official St. Leonard Dictionary", where Québecois and Italian come together and march boldly, arm-in-arm, through Inglese and out the other side.  I gather some of it is funnier if you actually HAVE a nona.

[Kipper4]

Did the drop box link work?
Is this enough information?

[Tony Forestiere]

The link worked as it should. Hmmm? About those voltages:

battery 8.2
Pin
1=1.482
2=1.482
3=0.964
4=0
5=6.79
6=0
7=6.8
8=7.76

Pin 8 should be almost 8.2
Pin 4 may say 0V, make sure it truly has continuity to ground
Pin 6, ditto
I think pins 1, 2, and 3 want to be around 1/2 of supply voltage.

You need to try to get your chip voltages close.
Someone will correct me if I am mistaken

edit: I am really unsure if pins 5 and 7 shound have a voltage if they are tied.
Fishing lesson?

[Kipper4]

ok that bad news then.
Somethings wrong somewhere
I already checked 4 and 6 and they both have good grounds.
Is it possible the chip is fried?
Is there a way of checking?
thanks for the response Tony (adds to buddy list)

[Kipper4]

The Shame of it.
OK i got it sorted now.
Thanks to Tony and his guidance on voltage levels.
I went back and double checked the voltages on those pins.
I couldnt figure out why i only had 1 volt abouts on pins 1,2,3
So i double checked the leads coming off the 22k resistors in the power supply. (at least thats what i think that bits all about.)
There was an extra lead going to earth.
So most of the charge was short circuited.
Thanks for making me check that
it works a treat now.

[Tony Forestiere]

I can't reply from work.  
Good. Glad you got that squared. From what I have learned on this forum: the voltages on most dual op-amps in MOST circuits want to be:
pin1 - 1/2 V+
pin2 - 1/2 V+
pin3 - 1/2 V+
Pin4 - 0V - (continuity to GND) A lot of folks figure if they are reading 0 volts, they are good without checking true continuity to GND.
pin5 - 1/2 V+
pin6 - 1/2 V+
pin7 - 1/2 V+
pin8 V+ - (supply voltage)

I wonder what pins 5 and 7 are now, and why? fishing lesson?

This circuit is just an embellishment of the traditional "op-amp booster/diode clippers to ground". MXR D+ comes to mind.

I saw in another thread that you were contemplating the purchase of a breadboard. BANG ON! Make sure you get some of the prescribed wires, or quality pre-bonded wire to use. You don't want to be shoving some sorry, twisted, stranded wire into the connection holes. When you get it set up, play with this: http://www.generalguitargadgets.com/richardo/distortion/index.html  

Have fun!

[Kipper4]

Thanks for the excellant article Tony and all the help.
I'll post up some new voltages when i get back from work tonight.
Cheers mates.