Possibly fried pedal, where to start

[Adamo]

Put Deoxit in all 3 pots and turned several times back and forth. Also wiggled all the chips and still no effect.

[armdnrdy]

Okay...

Since the indicator LED is turning on...the FET switching should be OK.

This might take a little while since there are nu component designations on the schematic or on the board....but....at least we have a drawing of the circuit.

What I would do now is build an audio probe.

http://www.diystompboxes.com/pedals/debug.html

We'll see what's going on with the signal...then we'll check various places depending on the probe results.

[Adamo]

Will do. Trying to track down the capacitor for the probe.

[armdnrdy]

Will do. Trying to track down the capacitor for the probe.

Any poly box, ceramic, mylar, etc. non-polar cap .1µf or larger will do fine.

[Adamo]

A higher capacitance will work also? How high?

[armdnrdy]

A higher capacitance will work also? How high?

I would say anything within reason.....

From .1µf through 10µf.

Use the next size above .1µf that you have or can purchase locally.

[Adamo]

Finally, the audio probe is done. Just a recap--- pedal passes a clean signal when either the pedal is engaged or not. I'm assuming pedal is 'engaged' because the led lights up. Is there an area or section that I should be probing to determine what's going on?

[Quackzed]

check the chips... look for audio or ticking....

[armdnrdy]

Don't worry about audio probing the transistors yet.
The schematic that we are working from doesn't have component designations (numbering) so...we wouldn't know which one we were probing without tracing the whole circuit.

Let's start with what we know so that we may narrow things down.

Attach the ground clip of the audio probe to ground somewhere on the effect.                               
Plug the ¼" jack into the input of your amp. Plug your guitar into the input jack of the delay pedal. Engage the pedal so that the indicator light comes on.

Gently lift the two electrolytic capacitors that are positioned horizontally over the 570 IC.
Using the IC pin out sheet that I posted below, look for the notch on the sheet and on the actual ICs for orientation.

While strumming your guitar:

Probe:
570 – pins 5, 6, 10, 15
MN3005 – pins 3, 4, 7

Take notes of your finding for each pin. Report back.

[Adamo]

Instead of using a guitar, I just played music through the pedal. I was able to hear the music pass through on all the pins that I tested, all with varying volumes.

Ok here goes:

570 : pin 5-- clean, quiet signal
        pin 6 --loud, clear signal
        pin 10 --- very faint signal
        pin 15 --- not quite as loud as pin6 and seemed muffled
    (*** none of these signals sounded 'delayed', just a clean signal in all case)

3005 : pin 3 clean signal, moderate volume
           pin 4 same as pin 3
           pin 7 louder clean signal
      (*** same as above , no 'delay')

[armdnrdy]

Okay...
Here's a question that I should have started with.

Since this delay has been in your possession...has it ever worked?

[Adamo]

Sort of. A friend gave it to me and asked me to 'clean it up' for him because it was very scratchy and the effect was working but barely. When I got it, the delay worked sporadically for about 20 min then stopped working altogether--- this was why I panicked and thought I 'fried' it.

[armdnrdy]

Did you mess with the trimmers at all?

[Adamo]

No

[armdnrdy]

Okay...what do you mean by "clean it up" and what was scratchy?

[Adamo]

The signal was very scratchy overall. When turning the pots it became even worse. When I first plugged it in it was as described above and the effect was fading in and out and then after about 15 minutes it cut out completely. I then opened it up and cleaned the pots with deoxit and started checking connections. Then I posted here.

[Adamo]

Is there a possibility that even though the led comes on that the pedal is not actually engaging?

Also (on a separate note), if a clean signal passes through the pedal when it's turned on does that automatically mean that one or some of the IC's are faulty?

[armdnrdy]

Is there a possibility that even though the led comes on that the pedal is not actually engaging?

Also (on a separate note), if a clean signal passes through the pedal when it's turned on does that automatically mean that one or some of the IC's are faulty?

The LED would still come on if the JFET (Q7 on the schematic) was bad. You are getting the "same" clean signal at the output as you are getting at the output of the BBD. I wanted to check the signal in other areas to see if there was:
A. signal
B. effect (delay)

The ICs seem fine. I have never encountered a "bad" BBD that passes any kind of signal....delayed or clean.

[armdnrdy]

Try something just to entertain me.

The trimmer marked 100K is the Bias trimmer. Put a small piece of masking tape on the two parts of the trimmer. The metal part that moves...and the stationary "body." Take a pen and draw a line across both pieces of tape. This will allow you to return the trimmer to the setting that it was in prior to you adjusting it. With the Delay (speed) control in the slowest setting, the Depth (mix) control fully CW....slowly move the bias trimmer around with a signal going through the effect. Listen for sounds of "life" (delay)

[Adamo]

Try something just to entertain me.

The trimmer marked 100K is the Bias trimmer. Put a small piece of masking tape on the two parts of the trimmer. The metal part that moves...and the stationary "body." Take a pen and draw a line across both pieces of tape. This will allow you to return the trimmer to the setting that it was in prior to you adjusting it. With the Delay (speed) control in the slowest setting, the Depth (mix) control fully CW....slowly move the bias trimmer around with a signal going through the effect. Listen for sounds of "life" (delay)

Still no 'sounds of life' whatsoever. Still getting an absolutely clean signal when pedal is engaged or not. Adjusting bias trimmer made no change in the output.