Possibly fried pedal, where to start

[armdnrdy]

With your meter...check the voltage at pin 2 and 4 of the MN3101. Let's see if the clock is "ticking".

If your meter reads frequency...take a reading at those two pins as well.

[Adamo]

With your meter...check the voltage at pin 2 and 4 of the MN3101. Let's see if the clock is "ticking".

If your meter reads frequency...take a reading at those two pins as well.

Both readings were 0.  

No frequency on my DMM.

(Btw, thanks for helping me out with this, I really appreciate it!)

[armdnrdy]

Double check those readings. Make sure that you're on the DC voltage scale.

Check it at pin 2 and 6 of the MN3005 as well.

[Adamo]

Double check those readings. Make sure that you're on the DC voltage scale.

Check it at pin 2 and 6 of the MN3005 as well.

Same readings again on the 3101.

Pins 2 and 6 of the 3005 also were 0. However, Pins 1 and 3 were 9.0 and 6.5, respectively (just to show that my meter is on and grounded).

[armdnrdy]

Now when I asked you to take the voltage readings...you were connecting the black lead of your meter to ground and the red lead to the IC pin correct?

[Adamo]

Yes, definitely. As a reference, do the other 3005 readings that I gave make sense?

Do the readings of '0' for the 3101 make no sense?

[armdnrdy]

The 3005 readings look fine.

The clock pins should be reading around half of the supply.

Check the power pins of the 3101. Pins 1 and 3.

[Adamo]

I'm getting 0's across the board on the 3101.

[armdnrdy]

According to the schematic that I posted...there are two diodes in series connected from +9 volts to the 3101s power pin (pin 1)

Do you have a diode function on your meter?

If the 3101 isn't getting power...one or both of the diodes may be bad.

On your circuit board the diodes are next to the 3101 marked 1S1588 X 2

[armdnrdy]

You might want to check for bad solder joints around the 3101 power pin and the diodes.

[Adamo]

Yes, I think I have a diode function.......there's a diode symbol right below the 'OHM 2000' setting on my meter. If I wanted to test them do I just touch both ends of the diode with the pedal turned on?

There seems to be some questionable joints. In fact the diodes look like they have some serious bridging going on. You can actually see them in the pic I posted in the top right corner of the board. But......wouldn't solder bridges cause a pedal to not work right from the get go.

If one or both of the diodes are 'bad' would that explain the pedal only passing a clean signal? Also, do diodes suddenly 'die'?

[armdnrdy]

You test diodes with the power off.
With the meter switched to the diode position, touch the two leads to both sides of the diode. If you get nothing...switch meter leads on the diode.

If the diode/s are bad....the clock IC doesn't get power. No power...no clock. No clock...no delay.

"do diodes suddenly 'die'?"

Have you ever had a TV stop working? PC monitor die?
Same thing. Components don't last forever. Who knows what this pedal has been subjected to in the past.

[armdnrdy]

I looked at the pictures. Those are pads not bridges.

What you think is a bridge is the connection of the two diodes in series. The other "bridge" is where both the diode and the 51K resistor connected to the 3005 are picking up power.

The power rail is the larger trace to the right of the 3101 and the 3005.

[Adamo]

I just tested the diodes and it looks one is giving me no reading at all and the other one is registering a number but it's bouncing all over the place ----- maybe I had too much caffeine today. Could it be the diodes that are causing the issue?

[armdnrdy]

"If the diode/s are bad....the clock IC doesn't get power. No power...no clock. No clock...no delay."

Try replacing both of the diodes.

You can replace them with easily sourced 1N4148 or 1N914. Both of these diodes will give you around .6 voltage drop. 1.2 volts in series.
In this application they are used to reduce the voltage going to the 3101.

[Adamo]

Will do. Should I 'bridge' them like they are right now?

[armdnrdy]

Remove the existing diodes..and install the new diodes in the same positions. Take note of the cathode band before removing the old diodes.

[Adamo]

That sounds great, I have 2 - 1N914's from another project. I'll pop those in tonight. I'll keep you posted.

Many thx!

[Adamo]

Hey Larry, just following up. Problem solved, swapping out the diodes fixed it. The pots still sound a little scratchy even after deoxit, I might just swap them out.

Many, many thx!

[armdnrdy]

Great to hear!

I always love a happy ending!