Hi I have tried to build a Dod 250. At the moment it doesn't work. Now I have noticed that the Schematic, below has a 1m5 resistor, R1 and a 10uF electrolytic cap, C1 that isn't on the vero layout, 2nd link below. Are these componants necessary for the circuit to work or are they just slighty different variatons of the pedal? Both claim to be the grey version. I have seen at least one other vero layout so I'm not sure I'm using the 'best' one.
http://www.generalguitargadgets.com/pdf/ggg_dist_g250_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/ulysses_77_grey_dod_od_250/ulysses_77_grey_dod_od_250_1_0.gif.html
Thanks in anticipation
Pete
Neither component is absolutely necessary, but they're good to include. R1 is a pull down resistor that discharges C2. Its only purpose is to stop popping when the bypass switch is hit. I don't think the original 250 had it, but it shouldn't hurt. C1 is a filter cap for the bias voltage. It makes the bias voltage independent of the op amp's bias current. IIRC, 1977 250s didn't have the cap, but later versions did. So, you can safely include or omit these components based on authenticity or functionality, your choice.
Thanks for your quick response. I will add both componants and continue my search for the fault.
Pete
check, and double check your soldering...not only for inadvertant bridges, but for bad solder joints in particular...they can lay your project low, bro...sometimes even if it looks good, it'll be screwy inside. keep your tip clean and tinned, and don't be afraid to re-heat connections and add a smidgen of fresh solder. can make all the difference in the world!
and remember to use a roach clip or something as a heat sink on transistors, diodes, and ic's...i have learned the hard way what too much heat can do!
good luck mate!
peace!
Thanks for the tip. Double and triple checkingsolder joints now now :icon_biggrin:
my pleasure, hope it helps, mate...i discovered that the joints on some earlier builds had failed, after them working fine for in some cases years...a little hot solder, and they're back in the saddle again!!
;)
rock on, and post pics and clips when ya get it sorted out!! i've been thinking about building one, too!
peace!
If I ever get it working I will.
I get sound to pin 3 but only a bit of static from pin 6. Pin 4 goes to ground OK and pin 7 goes to the battery ok. Pin 2 connects to R5 and C3 ok.
R3, both pots both jacks, d1, d2 and c5 all have terminals connected to ground so I am stumped.
the voltage readings pin 1 =0 NC
pin 2 = 1.12v
pin 3= 0v
pin 4=0v
pin 5 = 0v NC
pin 6= 1.92v
pin 7= 7.89v
pin 8= 0 NC
geez, can ya post the layout you're looking at specifically?
pin 1 =0 NC
pin 2 = 1.12v
pin 3= 0v
pin 4=0v
pin 5 = 0v NC
pin 6= 1.92v
pin 7= 7.89v battery is 'ok-ish
pin 8= 0 NC
The voltage divider should have 2x = value resistors strung from
Gnd. to V+, where they're connected should be in the middle of the power suppy: @9vdc supply, ~4.5vdc should be read at the divider node.
This node has a large resistor which pulls the relevant opamp pin to 4.5v bias, the other two [the other input pin and the output pin] should follow suit, and the +/- input pins will be 'center-ish between the two power rails, allowing room for the signal to swing +/- for a ways before hitting a power rail.
What is the voltage reading at the divider ?
Suspect the inputs could be connected to ground since they are all at a common voltage potential [o.ov], a short of the AC signal path to a DC reference will shunt ~everything AC to ground.
pinkjimiphoton
thanks
the layout is in my first link at the top the grey dod 250 on vero. I was comparing it to the schem in the other link i posted with it. The only changes I made were to add the R1 1m5 (actually a 1m) and the C1 10uf electrolytic cap I was originally asking about shown on the schem. I've added them again here
http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/ulysses_77_grey_dod_od_250/ulysses_77_grey_dod_od_250_1_0.gif.html
http://www.generalguitargadgets.com/pdf/ggg_dist_g250_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a'
petemoore,
I am getting 3.95v at the node thats where R4 and R3 join on the vero layout. I have just noticed the Schem shows a resistor of 470k (R4) but the vero has a 1m resistor (R2). It is the vero Im following so thats what i've put in but I'm not sure its correct?.
pin 3 is the one i guess your saying should be at about 4.5v it is def at 0. It is not shorted to ground. Neither are C1 or R1 (going by the vero componant labeling here).
GOT IT!.
Thanks you were right! I had 4v at the node so I had to have a bad connection not to get 4v at pin 3 right. It was the connection to R2. Looked a perfect solder joint but re did it to make sure several steps ago but I guess the leg wasn't far enough in the board. Gave it a shove in and I've got 4v at pin 3.
The circuit works.
I have built a. MXR Dist + and plan to put the 2 circuits together in one housing so I can just switch between them.
Thanks for all your time and effort.
If I keep making silly mistakes I may learn enough, one day, to help others. Lets face it if it had worked first time and would never have known why.
Pete
I don't understand how the resistor came disconnected. I mean I put the lead through the hole soldered it and then trimmed it. It can only have become disconnected later, perhaps when I was reheating all the connections.
Another thing I found, earlier, was that the input jack was shorting out. It was definately OK when I first wired it because I tested the two tabs to see which was which, so it became faulty later. Also when I checked the vero strips for shorts with my DMM it didn't show up as shorting out, thny a little while later it is shorting. So I don't know it just wasn't meant to be an easy build.
ahhhh the 250, one of my favs!!! I really like it! And it's quite an easy build! Congrats on getting over trouble and please post pics when boxed up!!!
Hmm, I'm having similar problems with my build. I used Renegadrian's layout and Neoclassic schem:
http://home.comcast.net/~snmavronis/neoclassic741sch9.jpg
Currently I get no sound, but the pedal comes on. Voltage readings are:
Pin 1: 0 V
Pin 2: 0 V
Pin 3: 6.18 V
Pin 4: 0 V
Pin 5: 0 V
Pin 6: 8.47 V
Pin 7: 9.11 V
Pin 8: 0 V
The 6.18 V on the pin 3 sound a bit off... Also wondering about the pin 6 voltage :/
There's not even any hiss coming thru. I added a true bypass according to this link:
http://www.little-black-box.co.uk/images/uploads/wiring-diagrams/3pdt-wiring.jpg
Any advices?
Are you using THIS (http://www.aronnelson.com/gallery/main.php/v/Renegadrian/250+grey+1_1.gif.html) layout?! I don't have one 250 handy atm, but yeah pin 3 is definitely way out of voltage! 9V go thru 100r, then a voltage divider (the 2 22k) and then 470k to pin 3. you should get around 4v but yeah can't make any readings on a true pedal.
I'd check that first. then, try to wire direct input and output, as the fx is always on, and see what happens...if that works it's the wiring of the switch.
Quote from: aranubanti on March 28, 2011, 07:07:14 PM
Hmm, I'm having similar problems with my build. I used Renegadrian's layout and Neoclassic schem:
There's not even any hiss coming thru. I added a true bypass according to this link:
http://www.little-black-box.co.uk/images/uploads/wiring-diagrams/3pdt-wiring.jpg
My NC schematic already included a non-pop true bypass wiring for the 3PDT. Is your alternate 3PDT true bypass wiring and output jack and/or footswitch signal wire connected correctly to the PCB? They are completely different from each other how they connect so you might have something confused between the two wiring schemes.
Quote from: Renegadrian on March 28, 2011, 08:42:14 PM
Are you using THIS (http://www.aronnelson.com/gallery/main.php/v/Renegadrian/250+grey+1_1.gif.html) layout?! I don't have one 250 handy atm, but yeah pin 3 is definitely way out of voltage! 9V go thru 100r, then a voltage divider (the 2 22k) and then 470k to pin 3. you should get around 4v but yeah can't make any readings on a true pedal.
I'd check that first. then, try to wire direct input and output, as the fx is always on, and see what happens...if that works it's the wiring of the switch.
Indeed that's the layout.
Gotta try that as soon as I get home again..
Quote from: Steve Mavronis on March 28, 2011, 08:48:29 PM
Quote from: aranubanti on March 28, 2011, 07:07:14 PM
Hmm, I'm having similar problems with my build. I used Renegadrian's layout and Neoclassic schem:
There's not even any hiss coming thru. I added a true bypass according to this link:
http://www.little-black-box.co.uk/images/uploads/wiring-diagrams/3pdt-wiring.jpg
My NC schematic already included a non-pop true bypass wiring for the 3PDT. Is your alternate 3PDT true bypass wiring and output jack and/or footswitch signal wire connected correctly to the PCB? They are completely different from each other how they connect so you might have something confused between the two wiring schemes.
Oh, didn't even realize yours was different.. :) It's strange because I've used the wiring in the link I provided before in my Tubescreamer build and it has worked perfectly. I compared the two side to side and theyre identical. So maybe the vero- board sucks... I get 9.11 V at the voltage divider junction, that's way off. Gotta check the connection... But you'd think it wouldn't deafen the pedal, only change the sound? So perhaps there's an error in my board.
Yeah I'm just thinking that the board layout you used is okay but the offboard wiring to the rest of the pedal is suspect. Double check that. Anything outside the circled PCB wire attachment pads on my schematic is probably going to be way different than the footswitch wiring pattern that you used. Mine is directly based off this article's diagrams (except I placed the LED resistor on the other side) and it works 100% completely pop-free on several sucessful builds I've done:
gaussmarkov: diy fx
Wiring Up a 1590B
http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b
(http://gaussmarkov.net/images/1590B_SETUP_COMPLETE.bmp)
Well, now I've soldered the switching appointed by you, and still no sound. I do not know why, but the votlage on the voltage divider changed now to 4,51 V. But on pin 3 it's 3,06 V because of the 470K resistor.
I keep coming to the conclusion that there's something wrong in my vero board, because I've checked everything else many times. It's just so uninspiring to try to rip the board off under all those wires..
Hmm, I made an audio probe according to the Geofex site and probed around a little, and the signal stops to the pin 3 of the 741. It's still there at the pin, but not on the pin 6 or 2. So perhaps it is the IC? Hardly believable as I've tried 2 of them already...
Well the problem got solved. It appears that it does matter if I connect the pins 1, 5 & 8. I cut the legs and it works now. Can't wait to test it with my 50 Watter...
Yeah, I thought you already knew about thoise pins! They are labeled NC (not connected) in my layout! Glad to hear it works, beware it will become one of your favourites too!!! :icon_smile:
I feel so stupid now... :D
Perhaps I should start taking advices literally as they say :)
There's still the pin 3 voltage problem, I'm getting only 3.07 V there. Before the 470K resistor it's 4.51 V. I suppose the 470K R is in there for a reason though..?
Why do you call it problem!? I guess it should be that way, see that resistor is there in every schem floating around.
I took my breadboard to see if the voltage is right.
Vin 9.64
Vdiv 4.84 (with 2 22k res)
V after the 470k 3.28
assuming that your supply gives out a little less than mine (unregulated) the 3.07 reading seems a regular value...
I'm a bit of a beginner with IC's :) It's just that I've understood from everybodys posts when they say that the "voltage divider halves the DC voltage for pin 3, so it should be 4.5 V" that it really should be 4.5 V :) But that clears it out, thanks a lot!
There's still the pin 3 voltage problem, I'm getting only 3.07 V there. Before the 470K resistor it's 4.51 V.
Must be the offset voltage of 741 ?
4.5v bias would be ok for pin 3, it'd have more centered bias and so the output would be a more symmetrical swing also.
That'd be nice if symmetric, clean output was desired.
The idea of the 250/D+ is so that the opamp output And the diodes both contribute to distortion.
The input has only to wiggle by some small amount that 3v seems to cover, the output swing is clamped at whatever the diode threshold voltages are for the back to back diodes clip the + and - at each diode [or diodes] foreward threshold voltage.
Renegadrian,
looking at your vero layout, i can't figure out how to wire the pots.
what type and value pots do i use?
can you provide a more details for wiring the pots.
How about the diodes - 1n4148? Will 1n4001 work ok?
thanks.
Dave, you're right about that, I didn't write everything, maybe I'll update that layout. I made it using MarkM PCB layout as reference, so you can just take values from there.
anyway, VOLUME is A100K and DRIVE is B500K. diodes are 4148 yeah.
I only wrote about pins 3 of the pots. DRIVE 2+1 go to ground as VOLUME 1, and VOLUME 2 is out.
I never used 4001 as clipping diodes, but I know they can be an easy replacement, so yeah they will work, dunno the difference in sound...hope that helps! :icon_wink:
yeah - helps a bunch man, thanks! can i bug you for one more question? What diodes are used in your layout of the Boutique NPN OD?
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3056&g2_serialNumber=2
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3071&g2_serialNumber=4
which basically is YAE (yet another Electra) - http://www.forrestwhitesides.com/files/up/img/layouts/electra_sch.jpg
or his derivatives Trotsky and lovepedal woodrow, and yes my version, Electradrian.
Still not finished-almost there but here is what it will look like.
http://s1228.photobucket.com/albums/ee448/geezer15/?action=view¤t=IMG_8465.jpg&newest=1
Shame you can still see the edges of the decal paper transfers! I don't have any knobs to fit yet. Can you believe the 20 odd I have are all the same size- too smal.
http://s1228.photobucket.com/albums/ee448/geezer15/?action=view¤t=IMG_8464.jpg&newest=1
The circuits are still wired as they were when tested so I need to remove all the jacks, pots battery clips etc and wire into the housing.
I followed the vero layouts except I didnt use a tantalum 1uf cap in the dist + just a metal film cap. It was physically large but fits ok and its what I had to hand. I don't know if it makes any difference to the sound. I like it anyway. I have used a A100k and have a C1m in the housing at the mo. Waiting for a C500K to arrive
thanks man, i have all of these parts so i guess it is next up!
Deleted
the C500K arrived and I've wired it all up and its working.
Just 2 minor issues. The pedal is noisy at volume. The two circuits are quite different in volume The Dist + is louder and brighter so I cannot just switch between the 2 circuits as the tone and volume controls need resetting. So leason learned -Next time I build 2 circuits in one housing I will put in separate tone and volume controls. I don't suppose I will want to just switch between the circuits so its, hopefully, not a big deal just thought I'd mention it in case anyone else is thinking of putting 2 pedals in one housing on the 'cheap'.
You could wire a resistor in series with one of the outputs to bring that volume down a bit so they match better.
-Joe Hart
Thanks, yes I'll look into that.
I know I'm reopening an old thread (and on a first post... >:() but I just wanted to acknowledge that this thread saved me many hours of frustration. In retrospect it makes perfect sense that NC on the schematic would equate cutting the unused pins. :) I was set to open a new thread, but the search command saved me here. I'm happy to say that I'm now ready to try to box up a DOD 250, or at least move to the next level on this particular build ;)
Thanks to all the comments here and to Renegadrian for posting the schematic for others to follow. I'm learning a lot along the way from everyone here and what I would consider small successes, but really more from the "failures" that just inspire me to learn more. There's an incredible amount of knowledge here, and I guess I just wanted to say thank you as it's helped me immensely. Apologies if I should have started a new thread, but I thought it made sense to post it here. If in the future I should do otherwise please let me know.
IMHO is a good thing to keep the forum clean, so it's ok to use an old topic with the same subject (that's what I always do)
Nice to read your words, yeah we all love the feeling when you just finished soldering, hook it up and it works...better than sex?!
XD
I am also happy and proud when someone uses my layouts, but do you know they're not free?! You have to pay in pictures of your build!!! XD it's mandatory!!! eheeheheh joking (pics are always good, we pedal pr0n lovers...)
thx for your comment!!! and yeah, welcome aboard!!!