Rebote 2.5 Delay debugging help needed (FIXED)

[Mihkel]

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. There is a slight high- pitched oscillation that can be regulated by turning the delay pot and the level pot regulates the level of the oscillation, but not the guitar sound. The repeats pot does absolutely nothing.
Subs: Lost my 240k resistor so I added a 180k and a 47k in series, got 225k.
Battery voltage: 9,4 volts out of circuit, 5,59 volts when connected to the circuit
TL072:
1:2,8V
2:2,76V
3:2,75V
4:0V
5:2,67V
6:2,68V
7:2,69V
8:5,43V


PT2399
1:3,95V
2:1,97V
3:0V
4:0V
5:2,32V
6:1,96V
7:0,55V
8:0,68V
9:1,95V
10:1,95V
11:1,95V
12:1,95V
13:1,95V
14:1,95V
15:1,95V
16:1,95V


If anyone could help, i'd greatly appreciate it.
Thanks

[Mihkel]

Forgot about subbing 47pf for the 51pf and 4p7 for 5pf. Those shouldn't make a difference, should they?

[Mihkel]

Noone? 

[didier]

Forgot about subbing 47pf for the 51pf and 4p7 for 5pf. Those shouldn't make a difference, should they?

indeed, those are acceptable changes


did you double check soldering? something must be wrong here because its very unlikely that the voltage of the battery drops that much when connected... (is it a fresh battery?)
maybe a short between the 5V after the regulator and the 9V?
a short between Vb and 9V?

[geertjacobs]

Is the effect already boxed or do you have it open on your table with long wires?
When testing I would really recommend separarting the pot wires as far apart as possible to avoid squeal.
It is really easy to generate feedback by having the input and output wires too close so feedback is induced.
At least that was my experience when debugging my PT-80. Mark Hammer has also provided me with a solution to lower the risk of squealing in my final build. A sreach will bring this up.

[Mihkel]

Thanks for the replies!
Geertjacobs: It's not in a box, the wires are quite short. The problem isn't the squal. The main issue here is the lack of delay.
What I don't understand is why my battery is giving out so little voltage when the circuit is on, but normal voltage when off. There aren't any short circuits, none of the parts get hot. I noticed that i had 22nf for a 10nf and 220k for a 100k, so I changed those, no improvement on the voltages or delay. All the other parts were the right values. Checked for solder bridges- none. Something must be drawing too much current in order to take the battery voltage down to 5,9V? I'd really like to get this thing going.


Thanks

[Mihkel]

Discovered a solder bridge going to the level pot. Removed that, nothing except the voltages changed. the battery voltage in circuit got up to almost 7V (woohoo   ) I have sound with the delay chip and voltage reg removed.
New chip 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

http://aronnelson.com/gallery/Nonworkingrebote25delay  - pics of the build
Thanks

[didier]

i guess something is still off because of a short somewhere or a messed up component
as the voltage reading on pin 8 of the opamp should be exactly the same as you put in the circuit (9V aprox.)

also, may i just say that it would be good to use a tad less solder. dont mean to comment or so, just good advice... you seem to be using just a little too much solder per joint.
a perfect solder joint should look like this: http://www.antex.co.uk/images/betterfig5.jpg or http://www.circuittechctr.com/guides/7-1-1-4.gif
not like these "balls" http://www.epemag.com/solderfaq/images/bad1.jpg

im sorry if i'm nagging, its meant to be good advice do what it what you want
just remember good soldering techniques can save you a lot of debugging time!

[Mihkel]

Thanks, I'll try to work on those when I get home today.

[Mihkel]

Went over the solder connections, removed extra wiring except pots, jacks and battery. Nothing. Battery voltage drops to 7 something V. I can't find a short anywhere 

[Mihkel]

Argh... getting embarrassing; third post in a row by me...
From GEO:

My (MXR Micro Chorus/EH Electric Mistress/ EH Memory Man/others) delay or chorus pedal doesn't delay/chorus/etc anymore, although sound comes through it in both effect and bypass positions. How can this be fixed?
    The delay chip is probably dead.

    This is one of those rare cases where you can have an effect that may not be fixable, at least not easily. If the analog delay chip is the Reticon SAD512 in the Micro Chorus and a Reticon SAD1024 in the others, the parts are not in production any more. While you can find leftover SAD1024's fairly easily (GEO has them, so do other places) there were never very many SAD512's made, and the 8 pin part is simply not available that I know of.

    The only easy options are cannibalizing another box that contains one, finding a leftover one, or hacking in one of the Panasonic MN3xxx series delay chips. This hack is almost certainly possible, but I have not seen one fixed this way yet. The MN3xxx parts are NOT pin-for-pin compatible with the Reticon chips, unfortunately. Since I originally wrote this up, Matshushita (Panasonic's parent company) has removed the MN3xxx series of delay chips from manufacture. There are still some stocks of them remaining, but they will become harder and harder to get.

    If you have a Reticon R5106 (may still be available), it can be plugged directly into the SAD512 circuit, but bias supplies will need tweaking to function. This is not a task for the weekend pedal fixer, though, as you need to understand the circuits to know what to change.

I hope this isn't my problem? The PT2399 is brand new from Banzai Effects. I'd hate to order from Germany for just one chip 

[Mihkel]

I ain't giving up on this yet!! 
I did an audio probe check on the pins of the PT2399 to see if anyone here could then confirm if the chip is dead.
Here are the results ( "-" mean 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 -

And still no delay whatsoever.

Before I order a new delay chip as my last option, could anyone confirm that the chip is indeed dead?

Thanks.

[Nasse]

Does the delay time pot + resistor measure just what it should to ground with ohmmeter? If I understood you get sound from "delay output" pin...

I have sometimes had luck finding solder bridges by looking the pcb against very bright light and with sharp needle or knife scraping off the flux/resin between tracks, and desoldering braid is good stuff. And you can check long thin tracks with ohmmeter if there is hairline cracks or imperfections because of etching (use some solder and wire on those if broken), and wires can be broken inside the insulation, and check the pots

I see you have used some silver colored caps that have terminals at each narrow side. I think they are very fine polyester caps but I have broken few of those because some my hand drilled pcbs had the holes  slightly off position and when forced the component in place the terminals got loose...

Luckily you have used sockets, so you can make new pcb and try chips on that, and if they don´t work then you can buy new and have two delays...

[Mihkel]

Thanks for the reply, Nasse!
The pot measures 46,5k, which is fine i suppose, the resistor is excactly 1k, if that's the one you meant. Which is the delay output pin? If you mean 4 or 6 I didn't get sound there.

The silver caps fit excatly into the holes.

Sadly, I don't own a laser printer, so i can't whip up another PCB so easily. I'd hate to keep bugging my friends with the printing.

Thanks

[Bagge]

It's a little hard to see, but from the picture it looks like a short between the silver cap ,027uF and resistor 12k. What is that extra green wire on the left side for? Looks like it's connected to ground.

[Mihkel]

No short, the top three connections need to be connected and the bottom ones, although it may look like they're shorted, are not. The green wire is indeed connected to ground and goes to the output jack. It didn't have an extra ground pad like the in jack did, so i just took the ground wire from there.

Thanks for the reply, and keep 'em comin, that way maybe we can get this thing delaying one day!

[Mihkel]

Old thread, I know, but maybe someone has any new ideas about this as I still can't get it working. 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

[Fp-www.Tonepad.com]

You say you did an audio probe... Do it again, this time, follow the signal path using the schematic (I try to draw the schematics in a way that shows this very clearly), probe on every single node. See where signal stops. That's probably going to tell us what the problem is.

Fp

[Mihkel]

Thanks for the reply, FP.

The problem is that I get normal sound out of the circuit, so I probably won't see where it stops. But I'll try again later.

[bancika]

also trace components from signal path to ground