Madbean Zero Point Mini Delay problems.

[steveyraff]

Hey guys,

Have problems with this build. This is the second one I built, had no issues first time round.

Its particularly frustrating, as I had it working perfectly until today!

R26 can be changed down to 68k to increase the modulation effect. Since changing this resistor, its not working. Now it just sounds like its bypassed, whether its on or off. Both the On LED and 'Rate' LED are working when its on, but there is no delay/modulation effect, it just sounds bypassed.

It could be anything really, I doubt its R26 - its just one of the risks with opening a pedal up and moving everything around. I noticed straight away I'd broke one of the ground wires, so I had to resolder that back on. I also since then have socketed R26 and tried a few different values, just to rule that out.

The only thing I can think of, is that I've done something stupid like accidentally leave the pedal powered while replacing R26, thus shorting something with my soldering iron etc. I've checked over and over for any solder bridges etc and can't find any at all.

I have a strange inckling that it might be something to do with IC3, the TL062 - but nothing more than a hunch due to its close proximity to the resistor I was replacing.

I am really bad with trouble shooting /debugging, mainly due to my lack of experience using a Multi Meter, which I've tried to figure out numerous times!

Can anyone think of what it may be - judging by the symptoms? Or what component would likely be first to go if I did short it? I presume it could be anything depending on where the short happened anyway...

Heres the project PDF:
http://www.madbeanpedals.com/projects/ZeroPoint/ZeroPointMini.pdf


Thanks for the help. Heres a pic of the two builds side by side. Its the red and purple coloured on I messed up.

[Luke51411]

There is not a lot of info to work with here. Post a link to the build doc and pictures of the actual board might be helpful. If you can take voltage measurements at each IC pin, that would be helpful. All you need to do is fix the black multimeter lead to ground and probe each pin with the red lead while in voltage mode on the multimeter. That is of course while the power is connected to the circuit.

[midwayfair]

No point in just guessing what it might be -- follow all the usual debugging procedures.

http://www.diystompboxes.com/wiki/index.php?title=Debugging

Also, neither of those look anything like the mini either ...

[steveyraff]

Also, neither of those look anything like the mini either ...

Lol How can you tell by looking at them aesthetically from the outside? (Although even by this, you should see all the exact same controls are present). I assure you, they are both the mini. I know this because I ordered the PCB's from Madbean, then received the PCB's with Zero Point Mini wrote on them.... then successfully built one using the Zero Point Mini PDF linked above. Actually, I successfully built both, until I went and screwed the second one up!

I'm really bad at debugging - partially because I rarely have to, I normally work meticulously so that they work first time. This one really pissed me off because I forgot myself while tweaking with it. Really frustrated with myself for that and for getting complacent.

Oh well... I'll check out that debugging link. Cheers.

[steveyraff]

There is not a lot of info to work with here. Post a link to the build doc and pictures of the actual board might be helpful. If you can take voltage measurements at each IC pin, that would be helpful. All you need to do is fix the black multimeter lead to ground and probe each pin with the red lead while in voltage mode on the multimeter. That is of course while the power is connected to the circuit.

Umm, this is odd. I don't know what the hell is wrong with me today - but I just made another stupid slip up... which seems to have fixed it?

This is weird. Someone explain if they know how this has happened.

I was taking Luke's advice, and got my multimeter out to check IC3, the TL062. Powered every thing up. I put the black lead to the Earth of the DC socket on the pedal, then put the red lead to first pin of IC3. Then, in another great moment of carelessness, my hand slipped so that the black leads tip joined the DC's earth and live pins. Suddenly the pedal started working again.

This seems weird. I still don't trust it. When I made the last one, they said with those IC's, the longer the delay time, the more it will create noise. That was true. But now I am not sure if I am imagining it or not, or if this one is now a lot noisier than usual. Could the TL062 still be to blame? Maybe I should order a new one just to be on the safe side :/

This truly is one of those days...

[duck_arse]

well, now you have to do a search on locking-up pt2399's.

[steveyraff]

well, now you have to do a search on locking-up pt2399's.

Is that what happened you think? The PT2399 locked up? I guess that would make sense!

[midwayfair]

Intermittent problems are usually the result of a bad solder joint. You'd do best to remove the project from the case and touch up any solder joints that look even remotely dodgey. Or at least toss it around a little (not even joking -- toss it on the couch, shake it like a polaroid picture, whatever you have to do to simulate being carted around in a car trunk) to be sure it doesn't reappear ... especially if it's leaving the house or going on your pedal board. If you made it for someone else, definitely touch up all the solder joints and solder the chip to the socket, because you don't want it coming back to you with the problem reappearing.

But in the case of the ZP mini -- there is a known issue where the PT will lock up. Duck's suggestion will lead you to the solution. You'll have to pull the board out most likely to correct the issue, so you might as well touch up the other solder joints while you're at it.

FWIW, the issue was brought up repeatedly on the MB forum, which I think has something to do with Brian redoing the project. You might want to "fix" your old one as well.

[steveyraff]

Intermittent problems are usually the result of a bad solder joint. You'd do best to remove the project from the case and touch up any solder joints that look even remotely dodgey. Or at least toss it around a little (not even joking -- toss it on the couch, shake it like a polaroid picture, whatever you have to do to simulate being carted around in a car trunk) to be sure it doesn't reappear ... especially if it's leaving the house or going on your pedal board. If you made it for someone else, definitely touch up all the solder joints and solder the chip to the socket, because you don't want it coming back to you with the problem reappearing.

But in the case of the ZP mini -- there is a known issue where the PT will lock up. Duck's suggestion will lead you to the solution. You'll have to pull the board out most likely to correct the issue, so you might as well touch up the other solder joints while you're at it.

FWIW, the issue was brought up repeatedly on the MB forum, which I think has something to do with Brian redoing the project. You might want to "fix" your old one as well.

Thanks man,

Yea I actually tried all that. Went over every solder joint with my jewellers loupe for a good close inspection. All fine.

The last one I made was for a friend, who gigs it regularly without issue.

Only update I have is that when I turn the pedal off, and back on again, it no longer works. That is of course, until I again bridge the earth/live pin of the DC like I mistakingly did the first time - that always brings it back to life for some reason.

I looked this up, and I seen those posts on the MB forum too. Some of them talked about earthing issues. It has me thinking, this pedal DID seem to work before I changed that resistor - and as stated earlier, one thing that did happen while moving it to change that resistor, was one of the earth wires broke loose.

Maybe I have an earthing issue here that is causing the PT2399 to lock up?

[Govmnt_Lacky]

Vintage & Analog with 2399s?

Is this supposed to simulate the vintage analog delays?

[steveyraff]

Vintage & Analog with 2399s?

Is this supposed to simulate the vintage analog delays?

Not really - I don't think so. The friend I built it for just wanted something that had short enough delay times that he could do slapback and echo stuff like old vintage pedals he was showing me and he liked noisy tape stuff. When I was looking up projects, Brian at MB had wrote in this ones description "The "Ring" switch is a hack I found which uses an additional feedback path from pin 13 to pin 9 on the PT2399
(something I've never seen before). In the Echo Bender, it is used to create crazy self oscillation. By 
modifying the resistance in the feedback path, I found that it creates a very dirty, tape­like repeat. 
Imagine a tape­based delay with the tape nearly worn out....pretty close to that." Thats all where that whole thing came from.

Anyways,

Back to the actual problem at hand. Following a few things I'd read about the PT2399 locking up on this, and earth issues sometimes being responsible, I re-wired and soldered all my earth connections. Its still doing the same. When powered up, not working, until I do that little temporary jumper on the DC pins to kick it back into life again. I wonder will replacing the PT2399 even solves this...

[steveyraff]

Think I solved the PT2399 locking (or I should say, latching) problem. Gonna explain it here for anyone else who might find themselves in a similar pickle, who may be searching the forum here for an answer.

One possible cause is the separation of analogue and digital grounds – pins 3 and 4 of the chip respectively.  Internally, these are separated by a 10ohms resistance and, in theory, the external digital and analogue grounds should be separate entities to prevent any digital noise finding its way into the analogue signal path.  However, it seems some (numerous) PT2399 chips don't like it when both grounds are kept distinct (the internal resistance is perhaps something other than 10ohms.

Joining Pins 3 and 4 seemed to do the trick for me. I'm still testing it - but so far, any time I fire it up, even after being left off for prolonged periods, its working.

Thanks to anyone else who chipped in with helpful advice.

[duck_arse]

stevey - head over to merlin's pages, look for jenny greenteeth. he details a pin 6 mod which might be of interest for all your pt2399 builds. (I still haven't started playing with these chips.)