Tap Tempo Chorus help needed.......

Started by brokenstarguitar, May 30, 2015, 10:03:30 PM

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brokenstarguitar

I just got finished with building the Tap Tempo Chorus from Sabrotone and I'm having an issue. My guitar signal stops at R1 but with my audio probe it totally disappears at C17. With the probe I have a HUGE volume reduction at R1 so i'm thinking the issue is somewhere in the beginning of the circuit due to the Volume loss with the probe and the complete loss of my guitar signal at R1.

Do these voltages look normal? Im not that good with voltages unless I can compare them to a working circuit. Maybe someone can spot something in my voltage readings. Please let me know if you have a direction for me to go. I went over everything I could possibly think of.

I don't want to flood the page with a bunch of pictures so you can see pictures of the build here....
http://s1300.photobucket.com/user/brokenstarguitar/library/TTC?sort=3&page=1

Here's a pic of the layout.....



Here's my voltage readings.
IC1 JRC4558D
1. 5.08
2. 5.08
3. 5.08
4. 0
5. 5.08
6. 5.09
7. 5.09
8. 9.49

IC2 attiny 85
1. 4.80
2. 0.14
3. 5.09
4. 0
5. oscillating from 0-5.08
6. 5.09- 1.02
7. 5.08
8. 5.09

IC3 MN3007
1. 1.42
2. 1.42
3. 2.16
4. 0.11
5. 0
6. 0
7. 0
7. 2.08
8. 2.08

IC4 MN3101
1. 1.43
2. 1.43
3. 0
4. 0
5. 0.64
6. 0.
7. 1.05-0.79 oscillates
8. 0.11

Q1
TOP – 9.94
Middle – 1.44
Bottom – 0.86

Q2
Top 9.94
Middle 4.70
Bottom 4.12

Q3
Top 9.94
Middle 4.51
Bottom 4.04

Q4
Top 0-1.39 oscillates
Middle 1.98
Bottom 1.42

Q5
Top 0
Middle 0.60
Bottom 0.74 oscillates to 0.44

IC5
Top 9.94
Middle 0
Bottom 5.09

slacker

Is the signal Ok at the top of R1, or is the problem already there? Your Q1 voltages look wrong, they should be the same as Q2. The top of R2 should be about 5 Volts because it's attached to pin 5 of IC1, so the middle row of Q1 (the base) should also be about 5 Volts. It looks like something is pulling the Voltage down. Try removing Q1 and then measuring the Voltage on the middle pin, does it stay at 1.44 Volts?
It could be a short between two tracks but I can't see anything obvious on you photos, the soldering and the rest of the board look very neat, nice work.

brokenstarguitar

I found my problem. I had R52 connected to the base of Q1, so I moved it up one row and tada. But now there's another small issue that I'm sure is an easy fix. My Multiplier pot works in reverse. Since there's only one wire coming from the board that would stay on lug 2 and I'd reverse the wires on lugs 1 and 3, correct?

Also got another question while I'm posting. Harold told me to do away with the remote option and to hook up the dpdt momentary tap stomp directly between pin 7 and ground. hooking up the tap input SW 3 to the center lug and lug 3 or 2 to ground. While doing this the tap led doesn't turn off. It does blink to tempo but there's no off. Does that make sense? Could my dpdt momentary be always on when it should be always off until tapped?