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Mihkel · Joined: 27 Jan 2006 Posts: 10

I built the Rebote 2.5 Delay using the PCB layout from tonepad.
http://www.tonepad.com/project.asp?id=51
The problem is that the guitar sound doesn't change at all, no delay. Pots do nothing that would change the sound. When the battery is connected to the circuit, the voltage drops; a battery that normally gives over 9V drops down to like 6 or 7 volts. With a power supply it stays near the 9V range, but still drops a bit.

Voltages:
TL072
1- 3,48
2- 3,48
3- 3,47
4- 0
5- 3,38
6- 3,45
7- 3,45
8- 6,91

PT2399
1- 5,00
2- 2,5
3- 0
4- 0
5- 2,88
6- 2,5
7- 0,55
8- 0,57
9 ->16- 2,5

Audio probe results:
( "-" means absolutely no sound)
1 -
2 -
3 -
4 -
5 Some hiss, that's all
6 -
7 Terrible static
8 Terrible static
9 Normal sound
10 -
11 -
12 Normal sound
13 -
14 -
15 Normal sound, but kinda muffled and darker.
16 -

Anyone have any ideas? Dead delay chip? Posted this on the diystompboxes forum, couldn't get a solid reply, I'm so desperate that even when someone would confirm that the delay chip is indeed dead, I'd be happier about this. Laughing

Paul Marossy · Posted: Sat Jan 28, 2006 12:38 am Post subject:

Did you actually etch a PCB or do it on perf?
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Mihkel · Joined: 27 Jan 2006 Posts: 10

I etched it.

Paul Marossy · Posted: Sat Jan 28, 2006 4:15 pm Post subject:

I'm afraid that I can't be much help other than recommending looking for bad solder joints, solder bridges, incorrectly installed IC chips and that sort of thing. Did you have any luck getting some answers at the DIY stompbox forum?
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Mihkel · Joined: 27 Jan 2006 Posts: 10

Could a bad solder joint really produce such symptoms? I've gone over the solder joints more than twice now. The chips are oriented the same way as on tonepad's layout. On the diystompboxes I got pretty much the same recommendations. I guess I'll just order another delay chip sometime. In GEO's FX debugging page it's said that no delay in a delay pedal is caused by a dead delay chip. But that was about analog delays. Don't know if it's the same with digital delays. Can't imagine how my chip could've died anyway, it's socketed, never did I reverse the polarity by accident or put it in the wrong way.

Thanks

Paul Marossy · Posted: Sun Jan 29, 2006 1:01 am Post subject:

Well, some chips are very sensitive to static electricity. Sometimes there is enough present from just the touch of your fingers to fry a chip. Maybe that's what happened. Is it cold and dry where you live right now? That increases the odds even more...
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Mihkel · Joined: 27 Jan 2006 Posts: 10

It's pretty cold here. Wow, I would've never thought that my problems could be caused by bad weather. Anyway, do you have any tips how to make sure my chips don't die because of static?

Thanks

Paul Marossy · Posted: Sun Jan 29, 2006 3:49 pm Post subject:

Mihkel · Joined: 27 Jan 2006 Posts: 10

Hi again.

I bought a new PT2399 and with a power supply it doesn't seem to affect the voltage. The regulator gives out 5V, that's about all the progress I've had, but still no delay.

Thanks

Paul Marossy · Posted: Sun Feb 19, 2006 8:53 pm Post subject:

johndroc · Joined: 20 Feb 2006 Posts: 1

I was just searching online, because I'm having the same issue!? I built the PT80 delay off the general guitar gadgets site
http://www.generalguitargadgets.com/index.php?option=content&task=view&id=48&Itemid=80
and seem to have the same symptoms. It's almost like the input signal (pin 16 for this one) is going to ground, when I run a tone through it and scope it. I had a bad joint on the "pre" side of the TLO72, but to no avail. I was thinking I might have fried something, but would static do this?

Paul Marossy · Posted: Mon Feb 20, 2006 3:28 am Post subject:

That is a strange one. Makes me think that there has been a changes in the design of the chip or something - like the pinouts have been changed. I doubt that is the problem, but it kind of appears to be somehing like that... Confused

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yngwie · Posted: Mon Feb 20, 2006 3:30 am Post subject:

in my experience the chip is the last thing to blame... unless you actaully smelt it cooking or it felt MEGAHOT when touched i doubt its dead...or soldered....lol big mistake there

you gota check and check and check and check
right parts
right polarity
right model
right area
right hole...

and seeing taht you etched a pcb did you compare it to schematic... coz maybe the pcb layout is wrong

Paul Marossy · Posted: Mon Feb 20, 2006 3:36 am Post subject:

Paul Marossy · Posted: Mon Feb 20, 2006 8:35 pm Post subject:

Hey, I just had a thought. Idea

Are you absolutely positive that your chip isn't in backwards? That could possibly be the problem. Question

Also, if the power supply exceeds 5V, it will probably fry the chip...

EDIT: Whatever the outcome, don't feel bad, it seems like 50% of people that build something with a PT2399 chip in it can't get it to work right, if at all. I think I may try building one of these PT2399 based delay circuits one of these days.
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