Mad Professor - Snow White Auto Wah [traced]

[abfackeln]

Has anyone had any success in breadbarding this yet, or are you still working on get the schematic finished ?

I believe the schematic is good to go now that the rectifier section has been updated (unless anyone sees anything else).

I have not breadboarded yet, but I am working on a layout, which is proving to be difficult on a single-sided pcb that will fit in a 1590B.

[Ice-9]

Has anyone had any success in breadbarding this yet, or are you still working on get the schematic finished ?

I believe the schematic is good to go now that the rectifier section has been updated (unless anyone sees anything else).

I have not breadboarded yet, but I am working on a layout, which is proving to be difficult on a single-sided pcb that will fit in a 1590B.

I've just looked at the latest schematic thats posted and one question i have is IC2a inverting input pin 2 has no connection to it, It looks like the junction of R18 and lug 1 of the sens pot should maybe connect to pin 2 IC2a am i correct in this ?

[analogguru]

Has anyone had any success in breadbarding this yet, or are you still working on get the schematic finished ?

I believe the schematic is good to go now that the rectifier section has been updated (unless anyone sees anything else).

I have not breadboarded yet, but I am working on a layout, which is proving to be difficult on a single-sided pcb that will fit in a 1590B.

Don´t waste your time - the schematic is still wrong, and - like normal - BJF didn´t contribute anything usefull to clear this matter. Read my previous post again - e.g. there is no reason why the junction of R29, R23 and R10 should not be connected to pin 13 of the LM324. the control path connection (pin 1/16 of the LM13700) ist still incorrect.

There's a Flubbydust from 1974....

The correct term is "Floobydust" and was brought up in June 1976 by Dennis Bohn of National Semiconductor. He wrote in the TOC of the Audio Handbook:

"Floobydust" is a contemporary term derived from archaic Latin miscellaneus, whose disputed history probably springs from Greek origins (influenced, of course, by Egyptian linguists) -- meaning here "a mixed bag."

Much more interesting is what you can find on page 2-10:

Audio (RF)-Rectification Elimination Tips:

- Reduce input impedance
- Place capacitor to ground close to the input pin or base (~ 10 - 300 pF)
- Use ceramic capacitors
- Put ferrite bead on input lead close to the device input.
- Use RF choke in series with input (~ 10µH)
- Use RF choke (or ferrite bead) and capacitor to ground
- Pray

analogguru

[Ice-9]

Has anyone had any success in breadbarding this yet, or are you still working on get the schematic finished ?

I believe the schematic is good to go now that the rectifier section has been updated (unless anyone sees anything else).

I have not breadboarded yet, but I am working on a layout, which is proving to be difficult on a single-sided pcb that will fit in a 1590B.

Don´t waste your time - the schematic is still wrong, and - like normal - BJF didn´t contribute anything usefull to clear this matter. Read my previous post again - e.g. there is no reason why the junction of R29, R23 and R10 should not be connected to pin 13 of the LM324. the control path connection (pin 1/16 of the LM13700) ist still incorrect.

i'm going back to read your post again now analogguru
A couple of points that may need attention after having a go at redrawing the schematic on paper.
1. I think pin 9 of the OPA needs to have a connection somewhere in the feedback circuit (near the resonance pot).
2. pin 7 of IC2B has to be the Vbias buffer but i expect everyone realises that.
3. Q3 the 5v reg looks like its labeled with the in/out the wrong way round. (I'm a bit confused on this one)

[analogguru]

Hi,

Well you would know if you have done your filtertheory what a Biquad is?

I really have no explanation why I always thought that a Bi-Quad-Filter IS a 2nd-Degree State-Variable Network:



Maybe it´s my age - maybe I am getting old ?
Sorry about my mistake.

analogguru

[abfackeln]

analogguru - thanks for taking the time (again) to review this - your input is always appreciated.

The compact layout and through-board vias (hidden under ICs and resistors) have made this RE somewhat difficult, and removing the components virtually destroys the pads (never had this problem before). And clearly others here have more knowledge with these types of circuits (and electronics in general) than I do.

Schematic in previous post has been updated again, although I'm not going to call it done - I'll leave that to someone else.

ag - you were correct - the junction of R19, R10 and R23 connect to pin 13 (IC2D) via C4.

Pin 1/16 of IC1 has also been updated - connects to R26/R31. That's the only connection I see at the moment without ripping up the IC again.

Ice-9 - with regards to Q3, if this datasheet is correct for the LM78L05 ( http://www.datasheetcatalog.com/datashe ... 8L05.shtml ), then the connection appears to be correct.

[Ice-9]

Ice-9 - with regards to Q3, if this datasheet is correct for the LM78L05 ( http://www.datasheetcatalog.com/datashe ... 8L05.shtml ), then the connection appears to be correct.

Looking at the datasheet and the refering to the pcb photo the input and output of the regulator Q3 are reversed (the datasheet for 7805 is viewed from the bottom)

[analogguru]

@Ice-9
You have to look at the datsheet of the 78L05 - it has the input at the right when you can read the markings.

@abfackeln
Anyway still some mistakes, read my post again.
Where pin 9 of the LM13700 is connected (except R14) ?
Where pin 2 of the LM324 is connected ?
and so on.

Take a multimeter (bepper in the diode-test position) to find out the hidden traces.

analogguru

[Ice-9]

@Ice-9
You have to look at the datsheet of the 78L05 - it has the input at the right when you can read the marking

analogguru

1. I've just rechecked and i still think the 5v reg is in the wrong way, surely the input must be at the 9v rail with the output feeding the collectors or Q1 and Q2
analogguru (am i missing something here as i think your saying i'm not correct here.)It doesn't make sense to me to have the OUTPUT of a reg connected to the 9v rail.
2. pin 2 of the LM324 needs connecting to the juntion of R18 and lug 1 of VR2
3. pin 9 of LM13700n needs connecting via a resistor probabally 4k7 to i think somewhere around pin 13 of lm13700 or the junction of R8 and lug 3 of VR1.

[abfackeln]

What can I say.... sometimes I'm a real knucklehead. Forest for the trees and that sort of thing. Filters obviously are not my sort of thing, but this has been a good learning experience.

analogguru - I've been using the continuity test on the DMM for most of the tracing, so I didn't have to rip up all of the components.

Ice-9 - it appears you are correct on the LM78 (looking at the datasheet I mentioned). I've reversed this in the schematic.
Pin 2 of the LM324 does have continuity between the juntion of R18 and lug 1 of VR2.
And pin 9 of LM13700n has continuity at the junction of R8 and lug 3 of VR1.
Schematic updated for both of these.

ag - I'm still not finding a capacitor connection (>100nF (up to 10µF)) at the output of the collectors of Q1/Q2.

Also poked around and still don't find any connection for pins 2 and 15 of the LM13700.

Thanks to both of you for your patience and guidance..... maybe we'll get this done soon...... (I'm sure I'm still missing something).

[analogguru]

Hmmm.... we are getting closer and closer:

analogguru - I've been using the continuity test on the DMM for most of the tracing, so I didn't have to rip up all of the components.

That´s the trick....

ag - I'm still not finding a capacitor connection (>100nF (up to 10µF)) at the output of the collectors of Q1/Q2.

Don´t care about it, it´s not there - simply because a solder-jockey lives in the phantasy that he is an electronic designer.

That you don´t stay uneducated the same way, here is something to read for you:

Also poked around and still don't find any connection for pins 2 and 15 of the LM13700.

Those pins are only to bias the linearization diodes if desired - they are unused in this pedal.

Thanks to both of you for your patience and guidance..... maybe we'll get this done soon...... (I'm sure I'm still missing something).

You could be right:
D3 is not a 1N4004. IMHO it will be a 5.1V zener-diode.
And I think source and drain of the FET should be reversed.

That´s all for the moment, now its 4 in the morning here and I need some sleep.

analogguru

[Ice-9]

D3 is not a 1N4004. IMHO it will be a 5.1V zener-diode.
And I think source and drain of the FET should be reversed.

That´s all for the moment, now its 4 in the morning here and I need some sleep.

analogguru

Yeah i agree D3 will be a zenner 5.1v for the led and the FET "drain" "source" are lablled the wrong way round.(just had another look at the photo and i think i can make out 85b marking on this diode so it may be a "BZY85B zenner )

also looking at the schem. and photo's D1, D2, D6 are not 1N4004 they look more like 1n4148 or similar.

Thanks abfackeln for keeping at this one.

[roseblood11]

also looking at the schem. and photo's D1, D2, D6 are not 1N4004 they look more like 1n4148 or similar.

1n4148 is correct, you can read that on the photo...

[Ice-9]

also looking at the schem. and photo's D1, D2, D6 are not 1N4004 they look more like 1n4148 or similar.

1n4148 is correct, you can read that on the photo...

Lol, at first i thought you eyes must be amazing but i didn't notice the pic was in such hi res, i've been reading everything from the thumbnal pics.

[roseblood11]

Yeah i agree D3 will be a zenner 5.1v for the led and the FET "drain" "source" are lablled the wrong way round.(just had another look at the photo and i think i can make out 85b marking on this diode so it may be a "BZY85B zenner )

I read "55B"
Maybe be a 1Nxx55B

[analogguru]

I would suggest that it is a BZX55B-5V1 from Vishay:
http://pdf1.alldatasheet.com/datasheet- ... 5B5V1.html

analogguru

[abfackeln]

You may have noticed that all of the diodes were labelled as 1N4001, when they were clearly not - I stuck these in as placeholders since this is my first project in Eagle, and it has way more parts available than I'm used to. Also wasn't sure of the glass-package types. Just haven't got back to update those...

roseblood - you're right, D3 has the marking of 55B - so I've labelled it as a BZX55 for now, per ag's suggestion.

D1, D2 and D6 corrected to 1N4148
Not totally positive about D4 and D5 - all I can read is 1N40XX.

ag - you're also right on the FET: source and drain were reversed. This is the same thing that got me with the LM78 (datasheet shows the bottom of the FET).

Schematic updated again. Thanks for everyone's input.... keep 'em coming.

[roseblood11]

D3 has the marking of 55B - so I've labelled it as a BZX55 for now, per ag's suggestion.

Ok, but is it really a 5.1V Zener? (=BZX55B-5V1)

[analogguru]

D3 has the marking of 55B - so I've labelled it as a BZX55 for now, per ag's suggestion.

Ok, but is it really a 5.1V Zener? (=BZX55B-5V1)

What´s your guess ? Could this be a "5", a "V" and a "1" ?

analogguru

[abfackeln]

So are we good with this? Do we have enough info? If so, I'd like to put it out on the 'bay to fund the next project.......