Need Debug help on Boss CE3 modded to CE2

[geertjacobs]

Could you try to do an AC measurement over the outer lugs of the Depth pot?
I would expect some AC measurement there.

If you're sure about the LFO section, then you should check the other components leading to the delay line:
especially check the orientation of Q9, Q10 and D11 and D12.

Don't panic about things not working immediately.
We all go through that :-)
That's why there's a great thread for it.

[Govmnt_Lacky]

Could you try to do an AC measurement over the outer lugs of the Depth pot?
I would expect some AC measurement there.

Tested for AC and there is none. Unless you count 1.5mV.

If you're sure about the LFO section, then you should check the other components leading to the delay line:
especially check the orientation of Q9, Q10 and D11 and D12.

Orientation of the trannys and diodes are in accordance with the schematic. Here are the measurements:

Q9 (5088)

C) 6.2
B) 0.6
E) 0

Q10 (5088)

C) 8.2
B) 1.53
E) 1.0

D11 (4148)

A) 3.6
C) 6.2

D12 (4148)

A) 0.5
C) 3.6

Don't panic about things not working immediately.
We all go through that :-)
That's why there's a great thread for it.

I have followed the debug thread. I am at the point where I need to get LUCKY.

I reflowd the solder on ALL of the LFO components. Still no change  

EDIT: Could a bad MN3102 or MN3207 cause my LFO problems? Could I have gotten a bad batch of BBDs? I have tried 2 sets with no change.

I will post ALL voltages according to the Debug and then pray for a miracle 

[geertjacobs]

Heh, I'm simulating the LFO from the CE-3 in LTspice and I get the same thing as you?!
No wobble and 1.3 VDC at the output...

[geertjacobs]

My spice sim had no power to the opamp and therefore no wobble, output was about 1.9V dc.
After connecting the missing link it works in LTspice.
Maybe something to check?

The output of the first opamp stage has a square wave from 0 to 9 Volts, the output of the second opamp stage has a triangle.

[Govmnt_Lacky]

OK... I thought I had a major breakthrough only to be let down once again!  

I noticed that I had my transistors Q6, Q8, Q9, and Q10 BACKWARDS!  

According to the layout I was given, the silk screen for the transistors is WRONG if you use a 2N5088. I dont know what transistors this layout and silk screen was based on but, it WAS NOT 2N5088s.

Now.... to the let down. I swapped those 4 trannys and there was...... you guessed it...... no change in the LFO  

So, here are the debug voltages for your viewing pleasure (There were changes after the tranny swaps):

IC1 (NE5532)

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

IC3 (MN3207)

1) 0
2) 4.3
3) 3.8
4) 7.7
5) 8.2
6) 4.3
7) 5.2
8] 5.2

IC4 (MN3102)

1) 8.2
2) 4.3
3) 0.6
4) 4.3
5) 0.75
6) 8.0
7) 2.7
8] 7.7

IC5 (NE5532) LFO

1) 8.5
2) 4.1
3) 4.3
4) 0
5) 4.2
6) 4.7
7) 1.3
8] 9.1

Q1 (all transistors are 5088)

C) 9.15 (put into Drain)
B) 4.0 (put into Gate)
E) 3.5 (put into Source)

Q6

C) 9.1
B) 4.3
E) 3.8

Q7

C) 9.1
B) 8.8
E) 8.2

Q8

C) 9.1
B) 4.1
E) 3.7

Q9

C) 3.7
B) 0.6
E) 0

Q10

C) 8.2
B) 2.3
E) 1.8

D9

A) 0
K) 9.1

D10

A) 0.6
K) 0

D11

A) 2.7
K) 3.7

D12

A) 0.8
K) 2.7

So there are my latest findings. I hope someone can see something. Maybe a bad part due to the tranny reversals??

[Govmnt_Lacky]

I just noticed that comparing the CE-2 and CE-3 schematics there appears to be an "extra" capacitor in the LFO stage of the CE-3.

If you look at the CE-3 schematic... C29 (10n) is installed between Pins 1 and 2 of the LFO op amp. In the CE-2 schematics, this capacitor is not there 

Also, on the CE-3 scheme, it appears that Vref to the LFO is coming from Q7s emitter to R46. In the CE-2 scheme, It is coming directly from INPUT POWER 

Sorry but I am grasping at straws with this circuit 

[SISKO]

I just noticed that comparing the CE-2 and CE-3 schematics there appears to be an "extra" capacitor in the LFO stage of the CE-3.

If you want this to be an exact model of the CE-2, dont install this capacitor. It works normally without it.

Also, on the CE-3 scheme, it appears that Vref to the LFO is coming from Q7s emitter to R46. In the CE-2 scheme, It is coming directly from INPUT POWER  

This ok. Q7 is an emitter follower (Vin = Vout), and your Vref is fine.

I noticed that I had my transistors Q6, Q8, Q9, and Q10 BACKWARDS!  

No big deal, but usefull information!
Just to be sure that the HF clock section is not screwing up things here, you could desolder pin 2 of the depth pot. This insures that the LFO section is isolated from the rest of the circuit. Now, check some voltages. Keep that disconnected until the LFO works.

Try replacing again with a new IC now that youve installed the transistor in the right way. I dont think that putting Q10 backwards would damaged the Ic, but just to be sure.

-Side note: Im intriged by the fact that you mentioned earlier that pin 7 climbed its voltage whenever you measured pin 6. This led me to believe that it does not have a solid reference to ground at pin 6 (could be a bad pot, but you checked that). Does it oscillate when you measure pin 6 (you could hear it working, but you should strum your guitar AND test pin 6)?

Debuggin can be sometimes a living hell, but thats the funny part of DIY also. Dont be dissapointed, Im sure its a silly mistake and we all been trough this kind of things (some of us still are).

Keep in mind that thar pcb desing could be wrong (reversed pins like pin 2 insted of pin3 are common mistakes). You could verify the pcb desing by yourself be comparing it with the schematic.

This is tested and working http://tonepad.com/getFile.asp?id=101

[Govmnt_Lacky]

Thanks SISKO. I will try these suggestions later this evening. Gotta work for "the man" right now!  

-Side note: Im intriged by the fact that you mentioned earlier that pin 7 climbed its voltage whenever you measured pin 6. This led me to believe that it does not have a solid reference to ground at pin 6 (could be a bad pot, but you checked that). Does it oscillate when you measure pin 6 (you could hear it working, but you should strum your guitar AND test pin 6)?

It is kind of odd. If I DIRECTLY test pin 7 of the LFO, I would get an instant reading of 1.3V however, if I read pin 6.... then go to pin 7....... it would INITIALLY read 6.8V then slowly trickle down to 1.3V and stay there.

[Mark Hammer]

I just noticed that comparing the CE-2 and CE-3 schematics there appears to be an "extra" capacitor in the LFO stage of the CE-3.

If you look at the CE-3 schematic... C29 (10n) is installed between Pins 1 and 2 of the LFO op amp. In the CE-2 schematics, this capacitor is not there 

Also, on the CE-3 scheme, it appears that Vref to the LFO is coming from Q7s emitter to R46. In the CE-2 scheme, It is coming directly from INPUT POWER 

Sorry but I am grasping at straws with this circuit 

The change in the LFO is very similar to what one sees on the BF-2 flanger, and is intended to eliminate audible ticking.  The idea is that the LFO start off with a waveform that is more trapezoidal than square, and turn THAT into a triangle.  The tick normally results from the sudden current draw of a square wave with sharp rising and falling edges.  You can read more about the strategy here: http://www.moosapotamus.net/IDEAS/stompboxology/MoTremLo.htm

[Govmnt_Lacky]

The change in the LFO is very similar to what one sees on the BF-2 flanger, and is intended to eliminate audible ticking.  The idea is that the LFO start off with a waveform that is more trapezoidal than square, and turn THAT into a triangle.  The tick normally results from the sudden current draw of a square wave with sharp rising and falling edges.  You can read more about the strategy here: http://www.moosapotamus.net/IDEAS/stompboxology/MoTremLo.htm

Thanks Mark. Now I have an understanding for the changes with C29 and Q7. A bit more knowledge is always great! 

Do you possibly have any ideas for my LFO problems? Beyond, of course, what has already been tried in this thread....

[geertjacobs]

Do you have access to an oscilloscope to compare the waveforms to the spice sim results?

[Govmnt_Lacky]

Do you have access to an oscilloscope to compare the waveforms to the spice sim results?

YES. I have access to a oscope, signal gen... DC to 1K, and a filtered DC power supply. I do not, however, have immediate access to a camera to post pictures of the oscope readings. Post or PM me the findings that you have and I will do my best to explain the comparisons.

Also, let me know EXACTLY where and how you want the circuit probed. As not to cause any errors due to misinterpretation.

Thanks for the help 

[geertjacobs]

Measure the outputs of the two opamp stages.

The output of the first opamp stage has a square wave from 0 to 9 Volts, the output of the second opamp stage has a triangle.

With "first stage" I mean the one with output going to the rate pot.
Second stage is the one going to the depth pot.

If the measurement is not ok, use Sisko's advice and unsolder the wiper (middle lug) of the depth pot and check again.

[Govmnt_Lacky]

Measure the outputs of the two opamp stages.

The output of the first opamp stage has a square wave from 0 to 9 Volts, the output of the second opamp stage has a triangle.

With "first stage" I mean the one with output going to the rate pot.
Second stage is the one going to the depth pot.

If the measurement is not ok, use Sisko's advice and unsolder the wiper (middle lug) of the depth pot and check again.

I will try to test this later this afternoon (it is 2p.m. here)

Hopefully I will have something around 4:30 or so.

BTW, could you give me the specific signal that you injected with your model? Was it Sine or Square? Frequency? Amplitude? (I usually use 200Hz at 100mA)

[geertjacobs]

I just simulated the LFO section.
It's intended to oscillate by itself, so no input signal needed.

[Govmnt_Lacky]

OK. I hooked the LFO to an oscope and put 9V regulated into the circuit. The results were as expected.

Pin 1 - 9VDC no modulation/square wave
Pin 2 - ~4.5VDC no modulation
Pin 3 - ~4.5VDC no modulation
Pin 5 - ~4.5VDC no modulation
Pin 6 - ~4.5VDC no modulation
Pin 7 - ~1.2VDC no modulation

There were NO square waves or triangle waves on ANY pins on the LFO. All were flatline DC indications

I will have to try disconnecting Lug 2 of the Depth pot and remeasuring.

Will post back as soon as I can with those results.

[Govmnt_Lacky]

Desoldered Depth pot Lug 2 and remeasured with oscope. Results were unchanged. Still no modulation in the LFO.

I guess I will try new op amp in the LFO spot and repost later.

[Govmnt_Lacky]

Replaced LFO IC (IC5) with another TL072 instead of the NE5532... NO GO!

Replaced C28 with another cap.... NO GO.

The only thing left to do is to replace C29 and replace both pots. After that it is down to resistors! 

[geertjacobs]

Do you have link to the layout?
I guess it won't hurt to double check the layout at this stage...

A continuity test for all the nodes of the LFO circuit is useful too.

It will be sooo rewarding when you solve this 

[Govmnt_Lacky]

Do you have link to the layout?
I guess it won't hurt to double check the layout at this stage...

A continuity test for all the nodes of the LFO circuit is useful too.

It will be sooo rewarding when you solve this 

I will PM you the layout that I am using tomorrow.

I take it that the fact no one sees anything wrong with my posted voltages that there is NO PROBLEM with them.

Well, I am finally at my breaking point.... literally!  

I totally removed the circuit from the enclosure and meticulously went between EVERY trace on the board with an xacto knife.
I resoldered a few points on the board however, none that applied directly to the LFO.
I read out ALL of the traces in the LFO... all are good with no apparent bridges.
I did notice that as I turn the RATE pot, Pin 6 of the LFO goes from 4.15V to 7.63V. Dont know what that means in the scheme of things!
I got desperate and cut out the 100K between Pins 2 and 5 in an attempt to mimic the CE-2 LFO.... that didnt help.
The only things left now are to replace BOTH 100K linear pots and replace C29.

After that..... it is to the shelf OR the circular file for this bad boy!!!!!