Yet another DBD question...

[dsgwin]

Hey guys,

I recently built the layout for the Mad Professor Deep Blue Delay, I am getting one good repeat out of it and then nothing else. The Mix and delay knobs are working as they should, however the repeat and volume knobs don't seem to be having any effect. I've swapped PT2399's I've tried probing the circuit to see if I am losing the repeats somewhere, but I am not having any luck. I saw that a few people on the layouts thread were having the same issue and were able to solve it but they didn't say what the issue was. Any help would be greatly appreciated!

Thanks,

Duncan

[toddvirgil]

Hey Duncan,

If you can post some pictures, it would be a huge help for us to see what's going on.

T

[dsgwin]

Here are the images, you'll notice that I had to combine resistors to make both the 360k, and the 33R, Other than that all the values should be the values used on the layout.

Solder Side:
http://www.flickr.com/photos/99378426@N06/9360731624/

Component Side:
http://www.flickr.com/photos/99378426@N06/9357960533/


Thanks again for your help!

-Duncan

[GoranP]

I see you got carried away drilling the holes, both in size and quantity.

Nothing really stands out at first glance except for some suspicious soldering in places... I see several potential solder bridges, although that can be the lighting in the picture. My first suggestion would be to knife all the gaps, thoroughly.

I also see that you shifted some components a bit but no obvious issues with that.

After that I'd check the ic power voltages, pt2399 can be temperamental if it gets anything short of 5V. I see you didn't socket your voltage regulator so check that too while you are at it.

Failing that, reflow all your joints. Most of them are pretty shiny but a few blobs seem strangely shaped so you may have a cold joint someplace.

[toddvirgil]

Yeah, I concur with Goran -- I think I might see a couple solder bridges in there too... Run a knife or hobby saw down each track a few times to make sure your not making any connections between the copper by accident...

[alltrax74]

Yep, ckeck solder bridges, specifically at row 8 col 3 and 10/3-4 (solder side)

Also i would advise you tu use different colours for the wires to avoid mixing them

[toddvirgil]

Oh yeah, and as always, it's a good idea to socket your transistors and IC's... Makes it much easier to swap out if you have a faulty component or just got the pin out wrong...

[dsgwin]

Thanks for all your help guys, I tried knifing the gaps and nothing seemed to change. The PT2399 is getting 5.14v at pin 1. I have a set up with a voltage drain on a pot so I can adjust the voltage if need be and even when I get it to an even 5v it doesn't seem to give me those repeats. I know adjusting the incoming voltages will also effect the rest of the circuit so it's not too accurate. I can't help but think it has something to do with the side of the circuit that the pot connects to, maybe some cold joints or a faulty pot. I will socket the regulator tomorrow and try swapping them out to see what I am getting. Does anyone happen to know what part of the circuit or pins of the PT2399 controls the feedback loop that would give me repeats and oscillation? I will also give you guys voltage readings on both ICs and see if anything is abnormal.

-Duncan

[GoranP]

I'd still reflow all the joints before all else.

From Brian over at Madbean:
http://3.bp.blogspot.com/-bEMBMvJwA5Y/TwrbbnpmzoI/AAAAAAAAAbw/EQ70PKQOFes/s1600/seaUrchin_Schematic.gif

You can see where all the pots are and which pin goes where.

As for the voltage readings, I can't help you with that as I don't have my DBD anymore to get readings.
I am planning to build one fully SMD when I get back from summer vacation but knowing my hectic life schedule, I'll be lucky if I build it before year's end.

[induction]

The PT2399 gives one repeat by default.  (Technically it gives a single delayed signal, which sounds like a repeat because it's mixed with the original signal).  You get more repeats by feeding the delayed signal (pins 12 & 14) back into the chip input (pin 16).


The fact that you have a single repeat means that the PT2399 is doing its job, no need to mess with the voltage.  Your problem is that the delayed signal is not reaching the pin 16 for some reason.  I'm looking at the following schematic:



Since signal is reaching the Mix (or Level) pot, the problem must be after the repeat and output paths diverge.  The only components or connections it could possibly be are the 2k resistor, the 50k Repeat pot (and ground), the 22n cap (and ground), or the 5k resistor.  My best guess: a bad repeat pot.

Reflow the solder joints to those components.  If that doesn't work, pull the Repeat pot and measure it.  If that doesn't work, pull each of those components one by one and measure/or replace them.

That should get you sorted.  If not, check back in with us.

[GoranP]

Wow... I love being taken to school again every so often.

@Induction: you really got skillz and I seriously enjoy your posts!

[induction]

Thanks, Goran.  If you really want an education create accounts at fsb and diysb and start reading. There's plenty of folks there that put me to shame, including the designers of many of the pedals we discuss here.

[dsgwin]

Thank you so much Goran and Induction. This has been a huge help!

Cheers!

Duncan

[GoranP]

Did you ever get it sorted out?