Build Your Own Clone Message Board

LED powers on but I get only a faint change in tone when engaged.
The knobs don't seem to change the tone.
The SPST switch 'pops' when thrown.

I've already inspected for weak solder joints but I only found a few to re-flow. Some pics are below. Thoughts?

https://picasaweb.google.com/118239162745341115871/Flanger?authkey=Gv1sRgCMGR5vOVzo-idA

Thanks!
Tom

Hi Tom, nice looking build!

Since the toggle switch pops, we know the signal path is working from the BBD's to the output. We need to find out if your LFO is working; take voltage readings at the middle lug of the depth pot (depth halfway to full up), and at pins 5 and 7 of the 3102. All of those voltages should be oscillating (going up and down) to some extent.

If you don't know how to take voltage readings, here is a tutorial: http://www.ladyada.net/learn/multimeter/voltage.html

Morgan, thank you for your help the kind words...I'm getting voltages oscillating from +2 to +4 at pin 5 and -0.5 to -2 at pin 7.

Correction: I had just checked between the middle depth lug and pins 5 and 7. Here are the three voltages when measured to ground:

middle depth lug: oscillating 0 to 4V
pin 5: steady 4.68V
pin 7: oscillating 0.1 to 0.5V

Did you report on the right pins? The IC's are orientated like this:


Pin 5 seems like it should have a higher voltage. Please verify that, and report on voltage from both sides of R51 and R52.

Sorry I did have 5 and 7 transposed...

Pin 5 is now oscillating steadily between 4.88 and 4.96V
Pin 7 is 3.65V steady
Middle depth lug is oscillating between 1.0 and 2.5V
R51 is oscillating between 4.85 and 4.96V on one side and 5.12-5.32V on the opposite side.
R52 is a steady 5.01V on one side and oscillating 5.12-5.32V on the opposite side.

Hey Morgan, wanted to see if you had any thoughts on those values. Thanks!

Hi Tom - sorry this slipped off my radar man. Voltages look good. Your issue is likely signal blockage between R6 and the two BBD's. Check out the schematic - look closely at all the components that are connected between R6 and the 2 BBD's. Check them all for value and I highly recommend resoldering all of those components. This is where a signal tester would be very helpful in isolating where the signal stops.

Hey no need to apologize -- thanks for the advice!

I took my audio probe to it but I have a question: should I have an audio signal at all points in the circuit?

I did notice there are several 'dead spots' near R6. For example, on one side of R6 (the side closest to C3 on the board) I have a signal but on the other side I don't. On D1, I have a signal on the non-stripe end and no signal on the stripe end. D2 is the opposite (signal at the stripe, no signal at the opposite end).

I'm looking at D1 as my possible culprit; it seems to be the first spot in the schematic that has an issue and it looks like the solder joint could be suspect. Thoughts?

-Tom

Didn't realize you had an audio probe. Here is the signal path you should probe:

R6, R7, R8, IC1 pin2, IC1 pin1, C6, BBD A pin3, BBD A pin 7/8, C9, C11, R19, R20, IC4 pin 2, IC4 pin1, R26.

That's the wet signal path. See if you can locate a spot where you lose signal and it doesn't come back. D1 & D2 form a clipping circuit to keep the circuit from runaway feedback. The circuit would work without them installed, so they are not the problem.

Morgan, I came up with this to indicate where the signal was present (in green) and dead (red):



I'm not sure how to interpret it (but that's probably obvious at this point). I did re-flow a few joints that looked a little solder-deprived before probing.

Thanks again for your help!

Nice job; the signal is dying at the output of the BBD. Now test both BBD's you have. Remove the ship from the BBD b spot, and try them both in the BBD a spot with the differential switch off. Then try them both in the BBD b spot with the differential switch on.

OK.

Neither chip in the BBDa spot with the differential off have a signal at pin 7.
Neither chip in the BBDb spot with the differential on have a signal at pin 7.
Also tried my 3208 chip in the BBDb spot at it had no signal at pin 7 either.

I don't see mention of the trim pot in your previous posts. Sorry if I missed it. Did you dial it in?

I hadn't set the trimpot but just had a go at it and still the same -- Sweeping the trimpot back and forth doesn't change the effect. This is with one of the 3207's in BBDa and a 3208 in BBDb.

Okay, this is pointing to a problem around the 3102. The voltages look okay, but there is something going on there that is preventing the 3102 from driving the BBD's correctly. This is probably a solder joint that looks fine, but isn't conducting well. You need to remove the 3102 from the socket and reheat each solder joint on each component on the schematic between the depth pot and the 3102, including the pins on the 3102 socket. See if that clears it up.

OK, did as advised in last post. There were some questionable solder joints indeed but I'm getting no change in effect.

OK, go back and retake voltages you already took for consistency, including all voltages from the 3102 & BBD's, from both sides of the large diode, and from the 78L05.

Voltage readings are the same as before:

Pin 5 is oscillating steadily between 4.88-4.96V
Pin 7 is 3.65V steady
Middle depth lug is oscillating between 1.0-2.5V
R51 is oscillating between 4.85-4.96V on one side and 5.12-5.32V on the opposite side.
R52 is a steady 5.01V on one side and oscillating 5.12-5.32V on the opposite side.

3102 readings:
pin 1: 5.01
pin 2: 0
pin 3: 0
pin 4: 5.01
pin 5: oscillating 4.88-4.96
pin 6: oscillating 0.11-0.24
pin 7: 3.65
pin 8: 4.69

BBDa:
1: 0
2: 5.01
3: 2.76
4: 4.69
5: 5.01
6: 0
7: 0.61
8: 0.61

BBDb:
1: 0
2: 0
3: 2.76
4: 4.69
5: 5.01
6: 5.01
7: 1.93
8: 1.93

Diode: 9.18 at anode, 8.43 at cathode

78L05 is 8.00, 0.0, and 5.01V

Hi Tom - sorry for the delay again.

It's getting narrower. You seem to have a problem with pins 2 and 4 of the 3102. Everything else on that chip looks good, and seems to be getting the supply voltages it needs. Pin 2 outputs voltage and connects to BBDa pin 2 and BBDb pin 6; pin 4 connects to BBDa pin 6 and BBDb pin 2. Both pin 2 and 4 of the 3102 should be in the 2.4 vdc range, mine both have a low oscillation of 2.46-2.48.

I'd like you to remove the 3102 from the socket and record voltages straight from the socket. I get the following from mine:
p1: 5
p2: 0.05
p3: 0
p4: 0.04
p5: 4.9
p6: 0
p7: 0
p8: 0.06

Morgan, you've been great to help so much...with the 3102 out, here's what I get:

p1: 5
p2: 0.2
p3: 0
p4: 0.2
p5: 5
p6: 0.01
p7: 0.02
p8: 0.01

I think it's time to look at replacing the 3102. Voltages are fine from the bare socket, but you're getting weird voltages when the chip is installed. There is no indication that BBD's are bad since you get the same symptoms no matter which one you use, and it's very unlikely both would be bad. Best thing is, if you have another pedal with the same chips that you know work, swap those in, if not, email BYOC (contact info on the contact page) and let them know that troubleshooting has lead us to believe the 3102 is bad.

Thanks again Morgan. My BYOC chorus is the older version based on the EH small clone so I haven't got any other 3102s. I will email BYOC now.

OK I got the new 3102 and finally had a moment to put it in and take some readings. I'm getting virtually the same numbers as the previous chip:

p1: 5.01
p2: 0
p3: 0
p4: 5.01
p5: 4.77
p6: 0.23
p7: 3.66
p8: 4.69

bumping this for advice