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 Post subject: Re: Bass Chorus No Sound
PostPosted: Sun Feb 11, 2018 1:12 pm 
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Slivertone wrote:
Do you mean the junction betwee C20 and R40? R 42 is far from C20. If it's C20 and R40, I get no voltage with or without the 3207 or 3102.

I meant to take the voltage from the empty bbd socket, pin 5. The c20 junction is where Vb is generated, but connects to pin 5. We want to see what pin 5 is getting.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Sun Feb 11, 2018 1:32 pm 
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Pin: Volts
1:0
2:3.3
3:2.8
4:6.4
5:6.9
6:3.3
7:0
8:0

pin 5 stays 6.9 with IC removed


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Sun Feb 11, 2018 3:19 pm 
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Seems like a bad chip. Contact BYOC directly for a replacement bbd & clock.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Sat Feb 17, 2018 1:46 pm 
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I just got the chips in the mail, popped them in, and it's still the same--sound on and off, but no effect.


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Sun Feb 18, 2018 4:43 pm 
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What's next?


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 3:25 pm 
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Can anyone help me get to the next stage of troubleshooting?

The voltages I had seemed to indicate some bad chips, but the new chips give the same result. I'm out of my element in the troubleshooting dept.

thanks


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 3:45 pm 
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I'll see if I can flag down Morgan for you. He's our best with this kind of circuit....

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 4:34 pm 
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Sorry!

Maybe there is a short on the BBD output. Pull the BBD chip from its socket. Measure resistance to ground from the empty socket at pin 7 and 8. You should have 56K to ground at both points. What is your reading?

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 4:46 pm 
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Speed reading through the post, I don't see where it's mentioned if you have set the trimmer. Have you tried that?


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 4:52 pm 
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Slivertone wrote:
The trim pot doesnt' affect it. I get 4.3v at 5 and 6.

:wink:

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 9:37 pm 
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I do get 56k at both pins 7and 8.


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Tue Mar 06, 2018 11:04 pm 
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Take and report all voltages from IC4 please.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Wed Mar 07, 2018 9:45 am 
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1:5.3
2:.84
3:.84
4:1.
5:6.2
6:5.3
7:0
8:5.0


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Wed Mar 07, 2018 3:06 pm 
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speed reading != good reading


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Wed Mar 07, 2018 6:10 pm 
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Sorry man - some of your readings are not making sense. Will you please verify that you are reading DC voltage, black probe to ground, chips are installed in their sockets.

Some of the readings look to be from the wrong pins. Please make sure you are reporting the readings for the correct pins. Here are the pinouts of the chips:

Image

Let's go ahead and take and report a full set of readings again from IC2 (MN3207 / BBD) and IC4 (MN3102 / clock ).

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Wed Mar 07, 2018 7:52 pm 
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Those readings were from MN3102.

MN3207:

1:0
2:5.0
3:2.75
4:1
5:6.2
6:5.3
7:1.1
8:1.1


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Wed Mar 07, 2018 8:04 pm 
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All with chip in.


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Thu Mar 08, 2018 5:24 pm 
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For IC4, the MN 3102, you reported the following voltages:
Slivertone wrote:
1:5.3
2:.84
3:.84
4:1.
5:6.2
6:5.3
7:0
8:5.0

Based on the readings from your 3207, I believe these voltages were reported backwards. Should be like this:
1: 6.2 (Vb)
2: 5.3 (connects to 3207 p6, which is also 5.3)
3: 0 (ground)
4: 5.0 (connects to 3207 p2, which is also 5.0)
5: 5.3
6: .89 (not connected)
7: .89 (LFO input - this is way low)
8: 1 (connects to 3207 p4, which is also 1, and connects to C19)

Please confirm that.

Things are beginning to take shape. Please check the following:

1 - your Vb voltage is low. Check your voltage at the striped side of the 1N4001 diode. You should have 9 volts there. Also check R42 - this resistor should be 100-ohms. If you installed a 10K or a 100K by accident, that would affect the Vb voltage. Please measure voltage on both sides of R42.

2 - Your 3102 LFO input voltage is very low (3102 pin 7). This could be because Vb is low, but also could be from R39 being a wrong value or having a bad joint. Check that out. Also, pin 6 and pin 7 are not usually the same. This could be a short. Measure resistance/continuity between 3102 pins 6 and 7. They should not connect to each other.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 12:14 am 
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Thanks.

I was reading the pins correctly, but I had put in the 3102 backwards.

pins 6 and 7 of 3102 do have continuity, though only with the chip in and powered up. There is no continuity in the socket, or with the chip when it's removed, or when it's installed but powered down. This is true of both chips (a second was sent to me.) I don't understand how that's possible, when they show different voltages to ground.

Here are the voltages now:

At striped side of 1N4001:8.76;

MN3102:

1:8.45
2:4.07
3:0
4:4.1
5:0
6:8.1
7:2.7
8:7.9


MN3207:

1:0
2:4.1
3:.9
4:7.9
5:8.45
6:4.08
7:3.8
8:3.8

Is there a diagram showing the location of components, like r42? I can find it on the schematic, but I'm not sure which one it is on the board.


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 Post subject: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 12:25 am 
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PCB map

Image

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 12:28 am 
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Voltages are much better now. Have you tested it with signal? Remember to adjust the trim pot (and set the mix knob at 50%).

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 1:39 am 
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r42 is 100.

I have tested with signal. Still no effect.


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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 11:19 am 
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Well, I don't understand what changed, but your voltages went from looking like there was no way the BBD would pass signal, to all of the clock voltages looking almost perfect and almost all of the BBD voltages looking good. The voltages now look like the BBD should at least pass some signal. Also, your BBD output pin voltages (3207 pins 7 and 8 ) are now right on at about 1/2 of Vb. Low voltages there are usually the culprit of the BBD not passing signal.

My main concern now is the input voltage to the BBD. That is pin 3 of the 3208. You have 0.9 volts there and we usually like to see something above 3 volts. Does adjusting the trim pot change the voltage at pin 3? Are you able to raise the voltage to over 3 volts?

If not, I suggest a couple courses of action:
- Do another reflow of the components around the BBD. Trust me, from experience I can say that sometimes it takes a few goings over with the soldering iron to correct that one bad joint that otherwise looks fine. Take the BBD out of the socket and reflow all the socket pins. Reflow R10-R14, C5-C8, and Q2.
- If that doesn't do anything, its time to listen to the wet signal and identify where you are loosing it. To do this, you use a BYOC Signal Tester or build an audio probe out of spare parts:
Image

With these tools, you can listen to the wet signal path and find out where the signal is lost. You would want to follow the following signal path:

IC1 pin 1 > R11 > R12 > R15 > 3207 pin 3 > 3207 pin 7 / 8 > R18 > R19

Let us know how it goes.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 12:09 pm 
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Would it be possible to get a larger photo of the full component side of the PCB than the one in your original post? Also with stronger lighting, if possible? I'm finding it difficult to distinguish color bands on the resistors, particularly the reds and browns. For example, swapping the positions of a 4.7K resistor (yellow-purple-black-brown-brown) and a 47K (yellow-purple-black-red-brown) can play havoc with a circuit. So confirming all of the resistor placements is often a critical piece of the puzzle when troubleshooting effect circuit problems.

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 Post subject: Re: Bass Chorus No Sound
PostPosted: Fri Mar 09, 2018 12:41 pm 
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I was able to adjust the pot to get pin 3 to 3v.

I reflowed all those spots. They look good. (I use jewelers visor, so I can see pretty well what's going on.)

I made the probe. If I mix the mix pot all the way over, I get no sound when plugged in normally. With that pot all the way over, with the probe I get signal (but no effect) all the way down the chain until pins 7 and 8 or the 3207-- nothing there and nothing past to r 18 and r 19.


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