Temperamental Deep Blue Delay

[phythian]

Hi all, first post here and I'm fairly new to pedal building.  Have had success with all builds so far, but the DBD (nocentelli's vero layout) is not starting every time for me, and I can't figure out why...

When it's not working, I just get the bypass signal (I have it wired to a 3pdt and it is definitely switching fine).  If I remove and replace the regulator, it usually starts the delay effect.  Same if I remove and replace the power supply plug, but only if I do it quickly - if I take more than 1 or 2 seconds between removing and replacing the 9V plug, it doesn't work.

I've tried numerous regulators (78L05) and the one in there now measures at right on 5V - when the effect is working.  However, when it's not working, the voltage sits lower, at around 4V.  All other voltages also sit around 1V lower than they should too (only when it's not working).  I've checked and rechecked my work and just can't find any mistakes in it.  Knifed all the gaps, cleaned the regulator socket holes, there's continuity along the tracks.  I don't get it...

I'm using a really heavy duty power supply - it's a great big unit normally used for commercial security systems, very well regulated at precisely 9V, 2.5A.  Could it be there's too much current for the 78L05's liking?

So any ideas on where the problem could be?  The good news is that I have an interim fix, using the power cycle I mentioned above.  But a more permanent solution would be nice, just need to know where to start looking  

Thanks in advance  

[bluebunny]

I'm not familiar with the specifics of the Deep Blue Delay compared with other PT2399 designs (nor with nocentelli's layout), but if the resistance to pin 6 is too low at the point of power-up, the PT2399 will latch up.  There are lots of threads around here that discuss the phenomenom and how to address it.  Or check the resistance to ground from pin 6.  Welcome, and good luck!

[arikam]

Hi, I built it using the same layout and had those problems.
It was solved by connecting PT2399 pins 3 and 4 via solder bridge, thus making sure pin 4 is properly grounded.

[nocentelli]

Sorry about that: I've had a look over some schematics for the DBD, and they seem to have either pin 4 grounded, or pin 4 connected via the delay pot to pin6 (and not grounded). No idea which schematic I must have used, but the weird thing is my works with almost no issues.... I'm going to open her up and ground that pin 4 now though.

[bluebunny]

I think that analyses that Merlin and others have done show that some PT2399s have pins 3 and 4 internally connected by a small resistance, but others don't.  Seems to be prudent to allow for both (or just join 'em together every time).  I've successfully built delays using designs where each method has worked.  Also had one or two 2399s crap out on me.  YMMV.

[phythian]

Thanks all, I'll go and warm up the iron once I've finished my coffee and woken up proper - sounds promising!

EDIT: Coffee consumed, iron warmed, pins bridged, and DBD is 100% reliable now 

Thanks very much all!

[bluebunny]

Cool.  Make sure you put aside a little time to play with your new creation.  Then it's off to the next build.  And the next.  And the next...   

[phythian]

Cool.  Make sure you put aside a little time to play with your new creation.  Then it's off to the next build.  And the next.  And the next...   

Definitely!  No further builds planned at this stage - I just finished a batch of stuff which I'm having some fun playing with now (the delay is part of a "multifx" board of sorts, in which 6 circuits were mounted in a shallow rectangular baking tray - a great way of cutting costs on enclosures, input jacks, DC jacks and patch cables!)

[bluebunny]

No further builds planned at this stage

Yeah, right...   

the delay is part of a "multifx" board of sorts, in which 6 circuits were mounted in a shallow rectangular baking tray - a great way of cutting costs on enclosures, input jacks, DC jacks and patch cables!

Head on over to the Pictures thread and post.  It's the law.   

[phythian]

Head on over to the Pictures thread and post.  It's the law.   

Done! - right here

[bluebunny]

Ha ha!      Nice job with that baking tray - looks great.