Mad Professor Snow White Fail

[anotherjim]

Wire joints failing under sleeving is a problem I know well. I've become loath to sleeve them unless there is a real danger of shorting or exposed high voltage. Sods Law that the joint you cannot inspect will fail. I prefer tinned stranded wire - 7/0.2 - for flexibility, but you must not damage any strands when stripping the ends. The slightest nick in the wire and a strand will break and stick out where it isn't wanted. Bitsbox and others sell pre-cut bundles of 7/0.2 in a selection of colours.

I suspect, if you use heatshrink sleeve and fit & shrink it while the solder joint is still quite hot, the solder can become wet again from the shrink heating,  and movement due the tube shrinking can pull the wire about leaving a dry joint which isn't obvious once the tubing is gripping it. So if you must heatshrink, let the solder joint completely cool before heating the tubing.

[pillo10]

Hi, My Snow White work bad too. My problem is that you hear only a continuous buzzing sound when I press the swich.The buzz up and down by operating the BIAS potentiometer, but also up and down a bit by operating the RESONANCE, but less.
My voltage readings are:

The input voltage is 8,95 v.

LM3234
1: 3,95
2: 3,95
3: 3,95
4: 7,95
5: 3,96
6: 3,96
7: 1,81
8: 3,91
9: 3,95
10: 3,96
11: 0
12: 3,96
13:3,96
14:3,96

LM13700
1: 1.2
2: 0.25
3: 3.97
4: 3.96
5: 4.45
6: 0
7: 4.45
8: 3.80
9: 4.30
10: 5.47
11: 7.95
12: 5.47
13: 3.95
14: 3.95
15: 0.40
16: 1.20

2N5457
D: 7.95
S: 4.05
G: 3.59

BC550
C: 4.95
B: 0.58
E: 1.2

BC550
C: 4.95
B: 0.02
E: 0.50

Any ideas please. I've been looking for the solution reading post and watching the electric scheme, but can not find it.

My knowledge of electronics are few, but I put a lot of effort. I have built several pedals and know more or less where I walk.

Thanks for your forum

[nickbungus]

Hi Pillo10

Sounds a lot like the issues I've had.

Which layout did you use?  If you see on one of my YouTube clips I had it working(ish).  Went back to it the next day and it was all noise again.

Did you read this?

I dont know why this one seems to be such a bitch (for me)?  I've made much more complicated circuits and had joy. 

Perhaps because its hard to debug?  I usually have success debugging by using a probe or by testing every component is connected to the other correct components by using the top of the board and testing connectivity using any exposed legs.  I also print a copy of the layout on paper and highlight a connection that has been successfully tested.  This method has served me well.

Its also worth identifying all voltage, ground and half voltage rails and making sure everything that should be grounded is, and everything that should be receiving a certain voltage is.

Chances are you know all this and better, just thought I'd offer what I do have to help.

[pillo10]

Thanks for your answer.


I am using the same layout that you put in the picture at the beginning of your post, I take it from http://effectslayouts.blogspot.com.es/. I checked everything that you mentioned but everything seems fine. I have printed the circuit and I have followed it. I tried to listen the first video you put, but It don't let me, then I don't know if  it is the same issue, may you send me the lick for listening it?. The mine only makes the buzz.

I have buy again the main components to check one by one. I've made much circuits, and I haved problems tha I could solve, but this is broken my head.

is yours working fine now?

thanks for your quick response

[nickbungus]

No mines still not working.  I'm going to give it one more shot with all new components and board then give it up if it fails.

I've already spent long enough on this trying to make it than I'd ever use it.  Still don't want to let it beat me.

[pillo10]

May you put again the video of failure?
Do you think I should open a new post with my issue?. I think this only read it you and me.

[nickbungus]

Both videos play just fine so it must be a problem your end.

Yes, I'd recommend opening a new thread.  Good Luck

[nordinator]

Hello Nick and other
I just solved  this afternoon the very bad sound of my SWAH V3 I made 1 year ago .
I spent so many time on topics and other to try to undrestand that I gave up .
I decided on last time to understand this problem and re solding few coumponents ( I am a car electronic technician so I know the soldering ...etc ) .

I discovered a missing wire on the schematic :
I have soldered the red wire on the middle of photo and the miracle happened , the same real sound of the mad professor pedal .
it is the 5v supply from the IC3 ( 78L05 ) who shoud goes to the Q2 , Q3 ,TR1 not wirtten on the schematic

Maybe it could help you , let me know if it is

Regards

[nordinator]

[nickbungus]

Hi Nordinator

Was there meant to be a photo with your post?  If so, please post again as I'd be very interested to see what you have done.

[nordinator]

Hi ( from Paris)
I checked your PCB plan and noticed yours is right about my missing wire .
I used this pcb and plan ( with the mistake ) :
http://www.guitarpcb.com/PDF%20Files/SWAH%20v3.pdf
Sorry I can't add my photo , the "insert image" doesn't work .

[nordinator]

how to add some photos pls ?
no icon or button works on my computer ( Mozilla and edge tried )  ,
sorry to be a pain .

[pillo10]

Thank you nordinator for your help, might you explain better?....

[Kipper4]

Nordinator
You need to host your images on a site like imgur then copy a link to the image in your post.

[bluebunny]

Nordinator
You need to host your images on a site like imgur then copy a link to the image in your post.

+1.  Put the picture URL between [img][/img] tags.  Use this button:

[nordinator]

aaaah ok
here is my solution :

[nordinator]

[bluebunny]

+1.  Put the picture URL between [img][/img] tags.  Use this button:

...and resize your pictures before you upload them.   

[duck_arse]

@ bungus, pillo, nordinator - and anyone else with a working snow white build - can you please post your voltages for the LM324 on your build?

the pin 7 voltages posted in this thread so far, working and not working, still all seem to be wrong, as far as my limited understanding of opamp workings goes. if they have V+/2 on the input pins, and they all do, the outputs must also be about that voltage, but pin 7 keeps being shown as near 0V.

why? how? and why is this bothering me so much? help!

[anotherjim]

If thy negative offset offends thee, strike out thy pull-up. R19.
For sure both inputs are at bias, but to make it so, with the positive input to pin 6 via R19, the op-amp drives the output low so the feedback resistor can pull the - input pin6 down to match the bias on the + input pin5.