Rebote 2.5 Problem - Please help

[zpyder]

Hey there...
So I finally got around to testing out a Rebote 2.5 on prefboard that I put together over the last couple weeks.  I did the layout myself, and it is at http://aronnelson.com/gallery/albums/rebote25/Rebote_2_5.gif.  It was verified by oldrocker.  It's not working, this is my first debug form, so here goes:

1.What does it do, not do, and sound like?
   With the effect bypassed, everything is as it should be.  Engaged, the effect is acting like a low-volume distortion.  The sound is distorted, the volume is lower than bypassed, and most importantly NO DELAY.  Knobs appear to have no effect whatsoever.
2.Name of the circuit
  Rebote 2.5
3.Source of the circuit (URL of schematic or project)
  Schem is at http://www.tonepad.com/getFile.asp?id=98, layout at http://aronnelson.com/gallery/albums/rebote25/Rebote_2_5.gif
4.Any modifications to the circuit?
  Well, no, but it's in my test jig not it's own box.  the test jig I made up recently is nothing more than a RACO box with a 3PDT switch, in & out jacks, power jack, battery clip, and 4 alligator leads coming out: FX in, FX out, +9v, and GND (connects to chassis via output gorund lug)
5.Any parts substitutions? If yes, list them.
  Not really... The schem notes that you can use a 10k, 11k, or other combo in place of the 15k - I used a 15k.
6.Positive ground to negative ground conversion?
  Nope
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>
  8.5v
Voltage at the circuit board end of the red battery lead =
  2.9v (!?)
Voltage at the circuit board end of the black battery lead =
  0.0v


IC1: PT2399
1: 1.57
2: .78
3: 0
4: 0
5 (N.C.):
6: .85
7: Looks like a capacitor discharging from around .05 to 0.0
8: 1.51
9: .06
10: .04
11: .81
12: .81
13: .81
14: .81
15: .81
16: .81

IC2: TL072
1: 1.48
2: 1.48
3: 1.46
4: 0.0
5: 1.43
6: 1.46
7: 1.48
8: 2.9


IC3: (Voltage regulator 78L05)
Vin: 2.9v
GND: 0v
Vout: 1.57v

No diodes...

Also... I have noticed that over the course of this testing, my signal has gone from about half volume & distorted to like 1/10th the volume and distorted... something is very wrong here...


I'll be off testing electros...

Thanks you R.G. for putting together some a comprehensive set of "oh shit" instructions...

Thanks!
zpyder

[zpyder]

Yes, I checked the 2399 pinout, and it looks to be seated properly.

[ranchak]

zpyder, I'm no expert, I just built a rebote 2.5 and it worked great. The next day I went to use it and it didn't work. I finally traced down the problem and then I had uncontrolled repeats and distortion. What it was was the battery. I had about the same voltage you did at the battery 8.67, but when powering the circuit the battery voltage drained at the + on the board. I still had about 4.8v at the chip. I hooked mine up to a wall wart and everything works like it should.

[oldrocker]

Pin 12 of the PT2399 is the delay signal coming from the IC.  I used an audio probe to fix mine.  If you put an audio probe to pin 12 and set the delay knob for long delay and when you play guitar it should have a delayed signal.  If you hear a delayed guitar signal than the chip is working and your circuit is working up to that point.   After that audio probe pin 14 to see if there's a direct signal coming out.
If you didn't make an audio probe I would suggest making one to debug this one.  Without it I never would've got mine to work.  I had 3 solder joint problems and 2 or 3 unconnected components.  I just traced the signal until I found a signal dropout and just kept fixing errors as I went along.  Your layout works fine but for tracing the circuit I used both the schematic and the layout to find my mistakes.

[zpyder]

zpyder, I'm no expert, I just built a rebote 2.5 and it worked great. The next day I went to use it and it didn't work. I finally traced down the problem and then I had uncontrolled repeats and distortion. What it was was the battery. I had about the same voltage you did at the battery 8.67, but when powering the circuit the battery voltage drained at the + on the board. I still had about 4.8v at the chip. I hooked mine up to a wall wart and everything works like it should.

Interesting... well I guess I'll try it out with a PSU tonight (or maybe on lunch break!).  I'll have to rig up the 9v jack on my new test jigerator... I'll take some pics of that too...

Pin 12 of the PT2399 is the delay signal coming from the IC.  I used an audio probe to fix mine.  If you put an audio probe to pin 12 and set the delay knob for long delay and when you play guitar it should have a delayed signal.  If you hear a delayed guitar signal than the chip is working and your circuit is working up to that point.   After that audio probe pin 14 to see if there's a direct signal coming out.
If you didn't make an audio probe I would suggest making one to debug this one.  Without it I never would've got mine to work.  I had 3 solder joint problems and 2 or 3 unconnected components.  I just traced the signal until I found a signal dropout and just kept fixing errors as I went along.  Your layout works fine but for tracing the circuit I used both the schematic and the layout to find my mistakes.

Hmmm... I thought 14 was the delay out.  Looking at the datasheet it's not clear to me.  Pins 14 & 15 are labeled "LPF2-OUT" and "LPF1-OUT" respectively, but I don't know what LPF means - lo-pass filter!??.  pins 12 & 9 are labeled "OP2-OUT" and "OP1-OUT" respectively - again, I don't know what OP stands for. 

Furthermore, referencing my layout, I don't see that pin 12 ever makes it to output, except through pin 13 which is labeled LPF2-IN.  14 is LPF2-OUT.

I did use an audio probe last night to see what I had.  At pin 14 I remember hearing what sounded like the unaffected guitar signal.  I'll have to do some more probing on 12.

It seems however that the voltage I'm starting off with is all wrong... If I'm only getting 2 to 3 volts in then that constitutes a problem, does it not?  Since this is the first time I've traced a circuit's voltages like this I'm not sure if that's normal or whack... If it is normal, what explains the loss of voltage?  Is the voltage "consumed" in the nets of my circuit here?

if someone could shed a little light on my questions here it would be much appreciated.

thanks!
zpyder

[oldrocker]

Yes you're right the incoming voltage is wrong.  Test continuity of pin 8 of the TL072 and the vin of the 78l05 since they both should connect directly to the plus voltage of the power supply (battery).  So if you're reading 9 volts at the plus battery terminal you would have to read 9 volts at pin 8 (TL072) and vin (78l05) also.  If not then what ever is dragging the battery voltage down to 3 volts is definately a mystery.  Shouldn't be too hard to track down though.  The area I would look at would be the vb circuit where the two 12K resistors and the 47uF cap goes to ground.  Something there would be dragging down your battery voltage.  Or maybe the pin out of the voltage regulator isn't right somehow.  Is the battery getting warm at all?  Just kicking around some ideas here.

[zpyder]

Okay, well my problem has been solved.  This is an interesting case I suppose.  All I did was rig up my test jig to a 9v (11vdc more accurately) PSU.  Then with the Rebote 2.5 clipped up to the tester, everything works GREAT!!! Sounds wonderful, what I nice little circuit.  When then pulling the PSU plug (and therefore auto-switching to battery power), the pedal fails once again exactly as before.  Listening to it, it is most certainly the PT2399 that is suffering the brunt of the lack of current since I can actually hear a half-assed single delay bounce back, but it is very low volume and distorted beyond recognition.  Interesting...

I really enjoy the modulation that occurs when you raise/lower the delay rate.  I prefer delays that do this to those that don't, because it can lend to some very interesting intro/outro/wigout passages.  Makes me want to install a jack fotr a wah-shelled potentiometer option on the rate knob.  This is something that was suggested to me by my drummer and I will probably do on at least one rebote build.

So anyways, plugging a solid PSU up to the unit has it functioning properly.  I guess that I can postulate that either the PT2399 or the 78L05 is drawing too much current for the battery to handle.  oldrocker - have you use yours with a battery to any success?  I wonder if the current draw on the 78L05 could be limited is necessary...

Some questions to be answered...  for the meantime, I've got me's a delay

zpyder

[oldrocker]

All my pedals are battery powered.  Only because I don't use them that much so the battery expense is small.  There was another thread I had read where someone had the same problem.  Their Rebote only works with a PSU.  Mine works great off of a 9 volt battery.  So that's very interesting.  One of the reasons I didn't build the PT-80 was because without the charge pump you needed a PSU.  I want all my pedals to work from a 9 volt battery at this point.   Of course you can use a charge pump to get the PT-80 working off of a 9 volt but I didn't realize it at the time. 
So I assume it's a new battery you're using so it's funny that the current draw is enough to drag  battery voltage down.  If you do make another one it would be interesting to see if you end up with the same problem.