Rebote 2.5 build report and troubleshooting

[studiostud]

Hey guys,

I've built a rebote 2.5 from a tonepad layout and now I'm trying to troubleshoot it.  Here is my build report data.  Hopefully we can figure this out.  Thanks in advance for any help.



1. Name of the circuit = Rebote 2.5 Delay

2. What does it do, not do, and sound like? Sound is coming through fine and the delay functions work.  Once you start rotating the pots, you start introducing a lot of noise and hiss.  The tone of the noise seems to change freqencies when you rotate the delay pot and noise increases when you increase the repeats pot.

3. Source of the circuit (URL of schematic or project) = tonepad.com

4. Any modifications to the circuit?  no

5. Any parts substitutions?
15K = 10K
24K = 22K
240K=220K
510K = 470K
0.027uF = 0.033uF
5pf = 5.6pf
51pf = 47pf

6. Positive ground to negative ground conversion? No

7. What is the out of circuit battery voltage? = 8.91

Voltage at the circuit board end of the red battery lead = 8.56
Voltage at the circuit board end of the black battery lead = 0.00


Q1 (78L05)
      
IN = 8.53
Common = 0.00
OUT = 5.05   


IC1 (TL072)

P1 – 4.21
P2 – 4.20
P3 – 4.17
P4 - 0
P5 – 3.44
P6 – 4.20
P7 – 4.20
P8 – 8.40

IC2 (PT2399)

P1 – 5.05
P2 - 0
P3 - 0
P4 - 0
P5 - 0
P6 – 2.51
P7 – 3.05
P8 – 0.59
P9 – 2.52
P10 – 2.52
P11 – 2.52
P12 – 2.66
P13 – 2.52
P14 – 2.39
P15 – 2.52
P16 – 2.52


Other Notes and Observations:

I checked all the electrolytic caps and all had higher voltages on the positive side.  All but one had 0V on the negative side.  The odd cap was the one right next to the "FP2005" on the tonepad layout.

[dschwartz]

1.- is the circuit in a shielded box?
2.- scratchy pots? (since you said the noise started when you move the knobs. check or just change the feedback pot..)

noise changing pitch when moving the delay pot= normal
hiss & signal a bit dirty= at long delay settings, kinda normal

[jlullo]

check out this link here:
http://www.diystompboxes.com/smfforum/index.php?topic=62512.0

I've made both the rebote 2 and 2.5, and had some crazy, hissy clock noise one time.  This fix killed it for me

*edit* oops... i'm sorry, i thought you were using the rebote 2.0 board

[studiostud]

1.- is the circuit in a shielded box?
2.- scratchy pots? (since you said the noise started when you move the knobs. check or just change the feedback pot..)

The circuit is not currently in a shielded box.  I have the negative lead from the battery going to the ring of the input jack which is also where I have the PCB ground going to as well.  The problem isn't scratchy pots, the noise changes with the rotation of the pots but doesn't go away if I'm not rotating them.  And the hiss is pretty bad and renders the pedal unusable.  Sounds like when an old television doesn't get reception and all you have is white noise. 

*UPDATE*  I did some further investigation and I narrowed the source of the noise down to the level pot.  I switched that out with a fresh one, but received the same results.     One thing I did notice was that the lowest volume of the level pot has the repeats at about the same level as the actual signal and turning it up only resulted in the repeats being much louder.  I found this odd cause delays I've used in the past usually have the unity volume at around 80%.

[studiostud]

I now the the circuit in a shielded box and I am still getting the same results.  I love any new feedback you can give me cause this one is driving me crazy!