My first build is (inevitably) not working - MXR Dist+

[ollie]

After spending lots of money on this stuff I still can't get anything to work! I've finally finished soldering my first vero layout the right way round (3 previously backwards,  ) and it's 'sort of' working. By that I mean that the drive pot alters the character of the sound and the voloume pot changes the volume. The only noise I'm getting out of it really though is a weird kind of oscillation (I will record a sample of this later, am posting this on my way out so I hopefully have some replies to look forward to when I get in ).

I've tried 3 new chips so far and have had the same result so it's not the physical chip that's wrong but I have a feeling it's the part of the circuit around there. There's a chance it could be my soldering but I took care not to have any solder run over tracks - there's none that I can see and I went down the gaps between tracks several times with a stanley knife.

The layout I'm using is this andy's one:



Which I followed closely bar two component changes: I didn't have any 10p caps so I used a 12p Ceramic disc cap and the lowest value Tantalum cap I have is 4.7u so I used a 1u Electrolytic instead

I can post some pictures along with voltages and sound clip later but didn't know if what I've given is enough info

Thanks for looking

Ollie

[guilds100]

i had the same problem.

http://www.diystompboxes.com/smfforum/index.php?topic=66083.msg524547#msg524547

[jefe]

i had the same problem.

http://www.diystompboxes.com/smfforum/index.php?topic=66083.msg524547#msg524547

I was just about to post, looks like there's a trace missing. 

edit: correction: looks like there's a cut in the trace that's missing...

I don't use vero, I prefer perfboard... but when I'm laying something like this out, I like to follow along with a highlighter on the schematic. I highly recommend this practice, because it will reveal these kinds of mistakes to you as you go.

[frequencycentral]

This missing cut in the track in this layout was discussed recently in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=75504.0

[ollie]

Thanks for your help, cut the track under pin 4 (between the 1 meg and the electorlytic cap) but now I get no output

I read here that it was the trace between the 1 meg and the 10p on the same row that was supposed to be cut instead but don't know if that's right or not

[MikeH]

This layout has been up with the same error for YEARS now.  I'm surprised Andy hasn't fixed it...

[frequencycentral]

This layout has been up with the same error for YEARS now.  I'm surprised Andy hasn't fixed it...

Never trust ANYTHING you read on the internet.............

.............hey, wait a minute.......?!?!

[ocg]

Thanks for your help, cut the track under pin 4 (between the 1 meg and the electorlytic cap) but now I get no output

I read here that it was the trace between the 1 meg and the 10p on the same row that was supposed to be cut instead but don't know if that's right or not

I believe that it should be like this:


P.D:
always use your schematic....

[ollie]

I believe that it should be like this:

...

P.D:
always use your schematic....

Yeah, that's where I cut but now no output. I don't have a schematic to work from, only that layout.

To follow the debugging thing, here are the voltages I get:

battery - 9.82v

pin 1 - 0v
pin 2 - 4.52v
pin 3 - 1.92v
pin 4 - 0v
pin 5 - 0v
pin 6 - 6.78v (slow climb up to this value from 6.4v)
pin 7 - 9.67v
pin 8 - 0v

if you need measurements from anywhere else let me know

[MikeH]

Google: MXR Distortion Plus Schematic, and you'll find one.  Also, go to tonepad.com, they have a dist+ project with a schematic on it.

[oldrocker]

When building any electronic project you should always have the schematic on hand to reference.  And when debugging an audio probe and learning to use it can save you lots of time.

[Mark Hammer]

Personally, I find the greatest source of nonfunctionality in projects made on perfboard, pad-per-hole or stripboard is simply the constant flipping back and forth.  When you have a PCB, you don't have to "imagine" the other side of the board; it's taken care of.  When the copper side isn't "taken care of" you can easily forget what's on the component side, and stuff gets connected to the wrong point.  Or, in the case of veroboard, one neglects to interrupt the connection between X and Y.

That's not a reason to avoid using any of those construction methods.  It's simply something you have to pay attention to a little more closely when using them.

You know what would really make life easy?  Transparent copper-clad board.  Wouldn't it be great if the board itself looked like the illustrations we work from, such that you could see the copper traces on the other side and would never have to do the mental flipping?

[frequencycentral]

Transparent copper-clad board.  Wouldn't it be great if the board itself looked like the illustrations we work from, such that you could see the copper traces on the other side and would never have to do the mental flipping?

I want some! I want some! 

[MikeH]

When I used to use vero, and now with pcbs, I always used to dram the layout on top first with a finepoint sharpie.  Especially helpful on vero.

[ollie]

Finally got this working, such a good feeling when you get the first one done! It's always the simple things that are wrong lol, forgot the cap next to the diodes 

Got a couple of mods planned already lol, gonna take a look at what other people have done as well. Might put a 470k resistor in series with the drive pot as most of the usable settings seem past half way, too clean before then. I've also got a couple of 12p1t switches so I'm gonna set up pairs of diodes so there'll be 144 types of distortion lol (I know the difference will only be slight but at the moment I'm feeling proud of myself lol). Off to look up the effects of different diodes, knew I picked up that mixed bag of them in maplin for a reason 

[ollie]

Sorry for the double post.

Was just Reading the cook your own distortion article again and it mentioned using CMOS inverters for clipping. How does that work?I don't remember seeing them used anywhere. Could I just replace a diode with an inverter? I guess not as they're not the same thing at all but I have an unopened pack of NAND chips I'm trynig to find a use for lol

[ollie]

Still waiting on the  12 pole rotary switches and I'm getting impatient so was looking around for other things I could add to modify it.

I want to add a tone control at the end and reckon this one looks pretty good:

http://home.comcast.net/~machrone/bjr/princtone.gif

Trouble is I don't have any 250k pots. Could I do something like use 100k pots and multiply the value of the capacitor by 2.5?

If not is something simple like this worth doing instead?

http://pic20.picturetrail.com/VOL1600/1048768/10737577/229732907.jpg

I mentioned before how I intended to add a resistor in series with the 1M pot as the lower end of the pot doesn't 'do' anything, I take it increasing the value is the right thing?

and finally, the 12 pole switch I intend to have different types of diodes for the first 6 or so poles and then multiples of diodes after so I can create asymmetrical clipping - is there a lot of difference between using, say, 1 diode on one side and 2 on the other and 2 on one side and 3 on the other? Will it affect it tonally or do more or less nothing?

I will try this out of course anyway but was hoping for some advice. I got a cool looking semi transparent box to put this thing in when it's done too so I'll post some pics

Thanks for all the help already