HELP!! Debugging Rebote 2 Delay pedal

[mitz]

http://www.tonepad.com/project.asp?id=27

hi, so i made this delay pedal a while ago. it didnt work but i figured it out that opamp was bad and replaced. and it worked!

today i went to play it but all of sudden again!, it doesn't work. bypass is fine but when pedal is on, there is no sound. I went through debugging and checked connections etc. but seems like parts are bad maybe?

i measured the voltage throughout I noticed pin #3 of IC PT2399 is zero and pin #4 of IC TL072 is also zero.

what does this mean???

please help me!!

im so frustrated as it was working...

[Enzo]

Everything works until it doesn't, you know...

They are supposed to be zero, they are the ground connections for those chips. it means that part of things is OK.

Is there +5 volts on pin 1 of the delay chip?

Is there +9 volts on pin 8 of the op amp?

Is there approximately +4 or +5 volts on pins 1 and 7 of the op amp.

If you have all that, then plug a steady signal into the input jack. A signal generator would be ideal, but otherwise plug a CD player or something into it - a nice strong signal. Set you meter to AC volts. Measure the signal at the input jack. Hopefully we will see maybe half a volt of AC.

Now is there at least that much AC on pin 7 of the op amp? If you are not sure it it is the signal you are measuring, turn the signal off and on (hit the pause button on the CD player) and see if the meter follows. How about at pin 1 of the op amp?

SInce you have no sound, I doubt it is the delay chip, since there should be some dry signal mixed in, and you're getting nothing. (Right?)

If signal makes it to pin 1 of the op amp, then is it also on the other end of that 1uf cap next to it? How about at the switch terminals?

All I am doing here is starting with a signal and following it stage by stage through the unit. You could have something as simple as a defective switch, a broken wire, a lose conection, a bad op amp, or...

[mitz]

Is there +5 volts on pin 1 of the delay chip?

Is there +9 volts on pin 8 of the op amp?

Is there approximately +4 or +5 volts on pins 1 and 7 of the op amp.

Hi Enzo!! thanx for reply!

I just checked a voltage on those pins.

pin 1 of delay chip is 5v

pin 8 of op amp is only 3.46v....maybe op amp is bad?

pin 1 and 7 are 4.6 and 4.4v.

so im guessing bad op amp for far??
but this thing happened before when I first tried this pedal and didn't work so I changed an op amp and it worked. but again, this happens. i just dont know why op amp keeps breaking.

any input??

thanx!!!!!!!!!!!!!!!!!

[mitz]

If you have all that, then plug a steady signal into the input jack. A signal generator would be ideal, but otherwise plug a CD player or something into it - a nice strong signal. Set you meter to AC volts. Measure the signal at the input jack. Hopefully we will see maybe half a volt of AC.

Now is there at least that much AC on pin 7 of the op amp? If you are not sure it it is the signal you are measuring, turn the signal off and on (hit the pause button on the CD player) and see if the meter follows. How about at pin 1 of the op amp?

SInce you have no sound, I doubt it is the delay chip, since there should be some dry signal mixed in, and you're getting nothing. (Right?)

If signal makes it to pin 1 of the op amp, then is it also on the other end of that 1uf cap next to it? How about at the switch terminals?

All I am doing here is starting with a signal and following it stage by stage through the unit. You could have something as simple as a defective switch, a broken wire, a lose conection, a bad op amp, or...

i tried this but i only gotta 0.4 since my meter only has 200VAC choice for measuring. and the rest 0.1 ......hmm i really dont know what to do.

i remember i wiggled with wires on switch and for a second, it worked so i resoldered it. also after that, changed a switch.

[Enzo]

The op amps runs on +9 and 0, so the signal leads - inputs and outputs - should sit more or less in the middle. The output pins are at right around 4.5, perfect, but I don;t know how that can happen with only 3.6v on pin 8.

[mitz]

i c
thank you anyways! i learned lots. maybe i will switch op amp..

[mitz]

Hi, Enzo! I resoldered some places and now it's working!!!!
thank you so so so much!!!!!

i really appreciate your help!!!!!

thank you!!!!