Newbie pedal build failure - could it be a bad chip?

[Philtre]

I've just completed a build of the Mad Professor Deep Blue Delay as per this vero layout - http://tagboardeffects.blogspot.co.uk/2012/02/mad-professor-deep-blue-delay.html (the vero layout is the first one there) and the delays don't work.

• I'm getting a clean, dry output. The volume control works, but there are no delays.
• The "Delay", "Mix" and "Repeat" controls do nothing.
• I've double and triple checked all solder joints, vero breaks, and jumpers
• I get the same dry output when I take the PT2399 out of its socket as when it's in its socket

Could it be that I have a dead PT2399? Is there any way to test this chip in isolation?

Voltages are (using a 9v battery which measures 8.8v):

PT2399
1 - 4.97
2 - 2.49
3 - 0.00
4 - 0.00
5 - 3.47
6 - 2.49
7 - 4.46
8 - 4.59
9 - 0.07
10 - 4.45
11 - 4.42
12 - 0.06
13 - 1.66
14 - 4.87
15 - 0.05
16 - 3.58

OP275
1 - 3.51
2 - 3.56
3 - 3.56
4 - 0.00
5 - 3.55
6 - 3.55
7 - 3.56
8 - 7.06

78L05 regulator
I - 7.29
G - 0.00
O - 4.97

[zombiesonore]

At this point you really need an audio probe.
It's real easy to build and save sooooooo much time and headache!
You will then be able to trace the audio signal and found where it stop.
Also do you have the schematic (it helps to follow the signal) ?

[somnif]

A picture of the board also helps diagnosis, if possible

[Philtre]

The schematic is here http://the7line.clan.su/_pu/0/92883033.gif

An audio probe sounds like a good idea. What do you recommend?

Picture of the board to follow (better in daylight).

At this stage I suspect a duff PT2399. So I'll try and find a simple test circuit that uses one and breadboard it.

[jimilee]

The schematic is here http://the7line.clan.su/_pu/0/92883033.gif

An audio probe sounds like a good idea. What do you recommend?

Picture of the board to follow (better in daylight).

At this stage I suspect a duff PT2399. So I'll try and find a simple test circuit that uses one and breadboard it.

Not necessarily, that circuit is notorious for locking up the chip. Do a search for that, it's an easy fix. Then if that isn't it, dig around and check your components, polarity, etc...


Sent from my iPhone using Tapatalk

[Philtre]

The problem is solved. 

Well, you see it was like this...nah, it was my own dumb fault. You know when I said "I've double and triple checked all solder joints, vero breaks, and jumpers". Wrong. I needed to quadruple check them, because a small smidgeon of solder was shorting out a couple of vero strips. So, it works now. And I shall stand in a corner with a dunce's hat on for the next day. But better than that I shall learn to more closely check my solder work next time.

Thanks to all who tried to help. 

And I really do need to get that audio probe together...

[Adam_DIY]

Lol we've all done it Phil and yes an audio probe is essential it's guaranteed more silly mistakes are on their way.  I once spent two hours checking for solder bridges, making sure components and tracks were in the right places etc when I realised I hadn't put an IC in the socket 

[stringsthings]

Lol we've all done it Phil and yes an audio probe is essential it's guaranteed more silly mistakes are on their way.  I once spent two hours checking for solder bridges, making sure components and tracks were in the right places etc when I realised I hadn't put an IC in the socket 

Exactly.  It's all part of the process.  The great thing about trouble-shooting is that oh-so-delicious feeling when
you solved the problem.   

Tip:  If you suspect a non-mechanical component is defective, it usually isn't.  Resistors, capacitors, and most analog IC's, are nearly bomb-proof.

How do you like your new delay?  Dont forget to post a photo in the build reports.

[Philtre]

I think I've probably learnt more about pedal building when something's gone wrong. For example, how to measure voltage readings, why those voltages are what they are, and the importance of really checking your soldering. ;-)

[bsoncini]

Whenever you use Vero you should use a razor blade/knife in between rows and if necessary use a multimeter to test continuity.

And yes. It's always nice when you build something and it works first try but you learn nothing except that you can follow a layout and know how to solder

[sonnyboy27]

For an audio probe, a lot of places recommend cutting apart an old cable. Rather than break a cable, just solder a ground wire and a capacitor to an input jack and put that on the end of a cable. Then you still have a good cable and and easily stored probe.

[Philtre]

Another, possibly newbie, mistake that has just cost me an evening is using single core 0.6mm wire for the interconnects between the veroboard and the sockets, switches and pots. I built a Lunar Module Deluxe pedal which suddenly just stopped working. Closer inspection showed that three wires had broken, presumably from all the flexing of moving things around inside the enclosure, and juggling things into position, and trying to make these wires as short as possible. I had to re-wire the the whole thing again to be on the safe side. I guess multi-core wire is better for this.

[EBK]

Anybody know a UK equivalent to the 24-gauge pre-bond stranded hookup wire that Smallbear sells?  I always recommend that stuff wholeheartedly, but I see our friend is in the UK.

[Adam_DIY]

I'd also like to find a new hookup wire the current stuff I'm using works fine but the coating often retreats from joints with the heat.  It ends up making some solder joints look uglier than they should be.  I'll have a look at the small bear stuff and try to find a European equivalent the postage from small bear to the UK is a killer. 

[Philtre]

What do you reckon to the Stranded 7/0.2 wire from Bitsbox?

https://www.bitsbox.co.uk/index.php?main_page=index&cPath=200_202