Need Debug help on Boss CE3 modded to CE2

[Govmnt_Lacky]

OK, so I etched a BOSS CE3 pcb from a layout provided from a fellow forumite. I decided to include some simple component changes to try to get it more into the CE2 spec. Here is the schematic:

CE3 - http://synthdiy.com/files/2007/bossce-3.jpg
CE2 - http://synthdiy.com/files/2007/boss_ce2.gif

Changes I made were as follows:

Changed R2 to 1K (and it comes AFTER C1 in the signal chain)
Changed R4 to 470K
Changed Q1 to a 2N5088 (and I twisted the leads to make it match the CE2)
I did not include the 220uF cap (C30 in the CE-2 spec) as it is replaced with C15 and Q7 in the CE-3 spec.

Basically, this circuit is a Boss CE2 modded to accept the MN3102/3207 BBD and Clock chips.

Now, with both pots at mid range, the trim pot at mid range, and an input voltage of 9.1V, here are my readings:
IC1 (4558)
1) 4.5
2) 4.5
3) 4.5
4) 0
5) 4.5
6) 4.5
7) 4.5
8] 9.1

IC3 (MN3207)
1) 0
2) 4.3
3) 2.4
4) 7.7
5) 8.2
6) 4.3
7) 4.7
8] 4.7

IC4 (MN3102)
1) 8.2
2) 4.3
3) 0.61
4) 4.3
5) 2.3
6) 6.5
7) 3.5
8] 7.7

IC5 (TL072)
1) 8.4
2) 4.1
3) 4.3
4) 0
5) 4.1
6) 5.8
7) 1.4
8] 9.1

ALL OF THESE VOLTAGES ARE SOLID. THERE IS NO LFO FLUXUATION ON ANY OF THE ICs.

My problem is that I get CLEAN guitar in both bypass AND going through the circuit. NO MODULATION/WET signal at all. This occurs throughout the ENTIRE trimpot rotation.

I can take transistor and diode readings if needed however, I am not sure there is a problem with them since the circuit appears to pass the clean signal.

I would greatly appreciate ANY and all help on this as I have A LOT of time and money wrapped up in this effect.

Thanks a lot

[Govmnt_Lacky]

Update:

I installed the 220uF electro cap as per the CE-2 drawings.... NO GO!

I also swapped the 4558 and TL072 with NE5532 dual op amps.... NO GO!

It looks like my LFO (IC5) is not wobbling like it should. All of it's voltages are static  Why could this be?

Could really use some help.

[geertjacobs]

Can you measure an AC voltage at the depth side (pin1 for the CE-2) of the TL072?

[Govmnt_Lacky]

Can you measure an AC voltage at the depth side (pin1 for the CE-2) of the TL072?

I will measure for AC voltage and post back later today. Could you explain to me why I would be looking for "AC" voltage on the circuit? I still have a hard time understanding the operational aspect of LFOs.

Thanks for the help 

[Govmnt_Lacky]

I measured the voltages at Pin 1 of the LFO... here they are:

DC = 8.4V steady
AC = 1.2mV steady

Something is causing my LFO IC to NOT oscillate. Shouldn't the voltages on all of the pins [except 4 and 8] be oscillating up and down according to the RATE pot setting?

So, my question to the forum is:

What could be causing my LFO not to oscillate? I know its not the IC itself (NE5532). Could it be the MN3102 BBD clock?

[geertjacobs]

The function of the LFO:
http://www.hobby-hour.com/guitar/chorus_effects.php

Are all your LFO components the right value? (No 100 Ohm instead of 100K, or 1nF iso 1uF,...)
Is your opamp mounted the right way?
Just to be sure: you are using the CE-3 layout? Then the output of the LFO goes to the depth pot. In that case the pin is pin 7 , not pin 1.

[geertjacobs]

- double post

[geertjacobs]

- triple post. need to stop hitting quote iso modify...

[Mark Hammer]

There appears to be a 100k resistor between pins 2 and 5 of the LFO.  I assume it is soldered to the pads on the copper side of the board.  This resistor is essential to providing the Vref that makes the LFO oscillate.  Is it installed on your board?

[Govmnt_Lacky]

There appears to be a 100k resistor between pins 2 and 5 of the LFO.  I assume it is soldered to the pads on the copper side of the board.  This resistor is essential to providing the Vref that makes the LFO oscillate.  Is it installed on your board?

Thanks for responding Mark. I REALLY appreciate it. I am actually about to dig into the circuit tonight again after I eat. I will try to get some more info on here for you and geertjacobs since you have both been assisting me.

Mark - I definitely have the resistor installed as you say. It is a 100K resistor between Pins 2 and 5 of the LFO installed on the copper side of the board. (I did sub the TL072 and 4558 by installing NE5532s in their place. I am also using some Visual Sounds MN3102 and MN3207 BBDs)

Geert - I will look over the components again to verify there are no mistakes. All of the ICs are properly installed as per the print/layout. I am using a layout that someone from the forum provided. This person I trust would not have given me an unverified layout. It is the CE-3 however, I DID perform the mods I described above (R1, R4, and Q1). I can put in a 2N5485 for Q1 if needed however, I don't think that is a problem.

I will post back again this evening after I get some food in me and about 30 min to look it over again.

Thanks for ALL of the help 

[Govmnt_Lacky]

OK, referencing the CE-3 schematic above, I have verified placement, values, and orientation of the following components:

R10, R51, R52, R50, R53, R49, R46, C27, C28. These are ALL of the resistors and caps in the LFO section.

I also verified connection of the traces between the Rate and Depth pots from the lugs.... through the above parts.... to the LFO IC. They are good.


SO WHY IS MY LFO NOT OSCILALTING     

[Mark Hammer]

This is a crowded board.  In these circumstances, I usually clean off the excess flux with some methyl hydrate, just to be sure that I am seeing all the traces for what they are.  The flux itself has no impact on the electronic aspects of the circuit, but it does have an impact on one's ability to see if there are any solder bridges, cold joints, or traces that run into each other.

So, are we all clear in that respect?

[Govmnt_Lacky]

This is a crowded board.  In these circumstances, I usually clean off the excess flux with some methyl hydrate, just to be sure that I am seeing all the traces for what they are.  The flux itself has no impact on the electronic aspects of the circuit, but it does have an impact on one's ability to see if there are any solder bridges, cold joints, or traces that run into each other.

So, are we all clear in that respect?

Way ahead of you Mark. Already cleaned the board AND i ran an exacto between all of the traces around the LFO to ensure there are no bridges.

One thing that I dont understand.... on the LFO, Pin 7 seems to be awful low (1.3V). Seeing as this is the OUTPUT for Pins 5 & 6, it caught my eye. Pins 5 & 6 are steady at around 4.2V each.

BTW... have I mentioned that the LFO is still constant and I can see my hair coming out? 

[SISKO]

R10, R51, R52, R50, R53, R49, R46, C27, C28. These are ALL of the resistors and caps in the LFO section.

Did you check C29?

You got pin7 low becacuse the voltage at pin 6 is greater than the voltage at pin5. The opamp is acting as a comparator.

Re-solder all the LFO parts. If all components are measured and chekced and they are ok, then this should do it

[Govmnt_Lacky]

Did you check C29?

Sorry, YES.... C29 is installed properly.

Since I installed the NE5532 chips, the voltages have changed slightly. On IC5, Pin 5 = 4.1V. Pin 6 = 4.4V. Pin 7 = 1.3V

There is not as big of a difference as when the TL072 was installed however, Pin 6 is still higher than Pin 5.

I cannot resolder right now however, I have ONCE AGAIN verified traces with my DMM. The only thing left to do is to verify ALL board traces with the DMM (not just the LFO part) or just scrapping and starting over! 

[Govmnt_Lacky]

Want to include in the post:

ALL transistors in the circuit are 2N5088 (even Q1 which I subbed to CE-2 spec)
ALL diodes are 1N4148

I hope someone can offer some more insight because I DO NOT want to scrap this board.

[SISKO]

You`ve come a long way to start over.
You got your entire circuit right (well, almost), the only thing thats not working properly is the LFO section, so we`ll focus on that for now.

You have your voltages right where we want them (at least at pin 2 and 5) and the outputs are acting normally (as comparators)
So i think that it hasnt enoguh gain (R49) or the integration part is not working properly. This could be a bad component value (but you already checked) or a bad solder. Thats why I recommend you to re-solder the LFO part.
Also, check your pots

[Govmnt_Lacky]

Thanks so much SISKO. I am really fried on this right now. I think I am going to sleep on it tonight and try again tomorrow.

I will look into R49 and also pull and verify the correct pots.

I will look into resoldering also tomorrow but I really hope it does not come down to that as it WILL BE A MESS!!

I will post results GOOD or BAD tomorrow.


Thanks all for the help. Hopefully tomorrow will bring success! 

[SISKO]

Keep in mind that resoldering means to heat the solder thats already on the pcb until it melts (again) just to ensure a good, firm, electrical connection.

You dont have to pull out the components and solder them again. If you are a little cautius, this should be an easy task. It wont look like a mess

[Govmnt_Lacky]

OK. I think I am officially at a shelving point 

I verified ALL components in the LFO section. They are all correct.
I verified ALL traces in the LFO section (including pot lugs) from component lead to component lead. They are all good.
i verified ALL traces and solder points for bridges/shorts. There are NONE.

Here are new voltages In accordance with the CE-3 specs. Input voltage is 9.1V:

IC5 (NE5532)

1) 8.4
2) 4.1
3) 4.27
4) 0
5) 4.13
6) 4.44
7) 1.38 (this one was weird. When I would go from Pin 6 to 7... the voltage would start at 6.8V and run down to a stop at 1.38V. I could ONLY repeat this if I went back to Pin 6 then remeasured Pin 7.)
8] 9.1

IC1 (NE5532)

1 thru 3) 4.5
4) 0
5 thru 7) 4.5
8] 9.1

IC4 (MN3102)

1) 8.2
2) 4.3
3) 0.6
4) 4.3
5) 2.35
6) 6.4
7) 3.66
8] 7.7

IC3 (MN3207)

1) 0
2) 4.3
3) 2.36
4) 7.7
5) 8.2
6) 4.3
7) 4.7
8] 4.7

Other than putting in NEW resistors and caps in the LFO section, I am out of ideas. (in the small chance that a resistor/cap is bad and/or mismarked)

I DID NOT resolder because I was able to get good readings from component lead to component lead.