Pefftronics - SB-101 Rand-O-Matic [schematic]

[digi2t]

Yes folks... it's here. I think this one stands right up there with the Ludwig Phase II, and I believe collectively, as with the Ludwig, we can break it.

Here is what I have so far. UKToecutter has taken charge of doing the schematic, maybe a clone PCB as well. I'll be more than happy to do the back tracing, verification, and answer all pertinent questions. I'm hoping the as the schematic develops our house brainiacs will be able to decipher the unknown IC's.

The component and trace picture are high resolution, so download them, and blow them up on your computer.

Control reference;


Trace side (note that the image is reversed, so I could use it to copy the components onto it);


Components;


Note that the two TL064's are upside down vis-à-vis the square pad indication of the board. There must have been an error in the original board layout. Follow my indications in picture.

Top side traces;


Ironically, I found that one of the 10K trimmers (above IC12) was actually broken. It controlled the amount of maximum feedback. For some reason, it had been pried off the board somewhat, enough to break the wiper lead. It explained why I found the feedback control rather weak. I removed it, and replaced it with a new multi-turn, and I have now adjusted it to where max feedback will take the input signal into runaway oscillation, which is kind of cool.

I'm going to go over it some more to ensure that there are no errors, missing connections, etc. The tantalum caps around IC1 are a bit of a crap shoot. Other than the polarity markings, there is no values on them. Measuring them in place with my capacitance meter, I get readings of 82nF to 88nF. They are slightly smaller than a 1uF cap that is on the board, so I'm making an educated guess here. I'm not really keen on removing one just to measure. IC1 looks like a dual opamp for mixing the dry and wet signals.

All input on the missing IC's will be greatly appreciated.

[Dirk_Hendrik]

Great work so far.
What seems absent, mainly because one will see other things than someone else, is component side pics.

edit,
nevermind. They're in the photobucket

[Dirk_Hendrik]

When attacking parts of the board as I did over the last 5 minutes I'd try to verify IC2 being a NE571, perhaps with one of the 2 companding sections unused.

[digi2t]

Great work so far.
What seems absent, mainly because one will see other things than someone else, is component side pics.

edit,
nevermind. They're in the photobucket

Ah, sorry about that. I should have put down the link.

https://s214.photobucket.com/user/digi2 ... t=3&page=1

[digi2t]

When attacking parts of the board as I did over the last 5 minutes I'd try to verify IC2 being a NE571, perhaps with one of the 2 companding sections unused.

Looking at other delay examples, it may very well be an NE570/1. Looks like a likely suspect.

IC7 and IC11 still no shows. What I can tell you is this power-wise;
- IC7 - +5v on pin 14, gnd on pins 5 and 8. Looking at the supporting cast, CD4016 maybe?
- gnd on pin 2, -9v on pin 3, and +5v on pin 13. Haven't figured this one out yet.

[Dirk_Hendrik]

For IC7 I'm going to put my money on a 4046 PLL

[apollomusicservice]

For me IC2, looks like NE570.

[Dirk_Hendrik]

Sharp Apollo!

However.... it might help to read the whole thread

[digi2t]

For IC7 I'm going to put my money on a 4046 PLL

Damn it Dirk, I don't know why I didn't think about that one. Especially with all the work I did on the Schumann PLL. Thanks again!

OK... IC11 is the only one left standing now, but I have to re-check the traces around IC9. I may have missed a ground bridge between pins there, that feed IC11.

Dang, I can't wait to breadboard this sucker.

[Dirk_Hendrik]

IC11 very much seems to change way the 555 operates. It does have some sort of 8-bit parallel input. Personally I'd draw it like a black box around the 555. With the 555 app notes it should come clear what type of function the part performs which in turn makes finding a suitable part more likely.

[Nocentelli]

So.. it's a randomly modulated delay that plays itself?



excellent.

[~arph]

IC11 = MC1408

https://www.physics.rutgers.edu/ugrad/3 ... 08-8_3.pdf

[digi2t]

IC11 = MC1408

https://www.physics.rutgers.edu/ugrad/3 ... 08-8_3.pdf

Dang arph... you beat me to the post!

Many thanks to you and R.G. for unblocking this one.

[Dirk_Hendrik]

And thats one I would never have come up with, making this thread a brilliant piece of collborative knowledge

[digi2t]

Alrighty then...

I've traced, traced, and double traced, and this is what I have to date (click on images to get larger images from Photobucket);



And, the schematic that Andy has developed from it (ignore the rotary switch LED's, that's a possible add-on);



I have this monster on the breadboard right now. Sweeping the mix pot, full dry side is loud and clear, full wet side is at a lower volume output, but no delay, modulation, or random at all. I have signal up to the 571, and after the 571 to the 7569, but nothing coming out of the 7569. Right now I'm wondering if I've missed something in the trace, or if the 7569's that I bought are duds.

Major head scratching going on here. Bum chip? Bum breadboard? Bum trace? Grrrrrrrrr.... Anyone see something I'm not getting here?

[grizzlytone]

Alrighty then...

I've traced, traced, and double traced, and this is what I have to date (click on images to get larger images from Photobucket);

[ Image ]

And, the schematic that Andy has developed from it (ignore the rotary switch LED's, that's a possible add-on);

[ Image ]

I have this monster on the breadboard right now. Sweeping the mix pot, full dry side is loud and clear, full wet side is at a lower volume output, but no delay, modulation, or random at all. I have signal up to the 571, and after the 571 to the 7569, but nothing coming out of the 7569. Right now I'm wondering if I've missed something in the trace, or if the 7569's that I bought are duds.

Major head scratching going on here. Bum chip? Bum breadboard? Bum trace? Grrrrrrrrr.... Anyone see something I'm not getting here?

Hi Dino! Remember me from way back? I've been down with the flu for the last couple of days so I've had time to catch up with the dealings of the stompbox community. You seem to have hit the proverbial brick wall with this rand-o-matic project. I think I know the feeling - it's a constant itch that you just can't scratch right? About 5,5 years ago I got a broken R-O-M of of ebay. Replaced the broken DC-DC converter IC and naturally had to draw up a schematic in order to figure out how it works. The schematic is large and kind of unstructured with notes to myself and also some mods that I seem to have decided on on the spot. The mods are designated with circled numbers. I don't have access to the pedal at the moment but I remember for certain that I implemented a ON-ON-ON-switch mod -very easy, just replace the ON-OFF-ON-switch to achieve randomness superimposed upon the triangle LFO when the switch is in the center position -nice!. I can't remember for sure whether or not I replaced the 6-p rotary switch w/ a 10-p in order to take full advantage of all delay times that the division of the CD4040 offers.
Anyway, after a couple of frustrating attempts to downsize the 600 dpi scan of my handdrawn schematic to a size acceptable to FSB I gave up and uploaded the scan to my dropbox account: https://www.dropbox.com/s/rudbtjjz6hcqx ... t.tif?dl=0
You can download it from there.
I hope you can find the answer in there as to why your breadboarded R-o-M doesn't work. I would love to help out more but I just don't have the time to do a detailed comparison of the schematics.
Good luck buddy!
/grizzlytone

[digi2t]

Dang Grizzley!! THANKS!!!

Yes, the itch is still there, and it still needs to be scratched, but I've been occupied with so much other stuff of late, that it just sits there on the corner of my bench. Laughing at me.

I'll look over your sketch, and compare it to what we have. Might end up being something really stupid, or it might just be that I got a bum component.

[jrfox92]

Did this ever go anywhere?
There have been a few more images that have popped up since the original thread, but it seems like all work on this was halted over a year ago.

[digi2t]

Still trying to make it work. I feel like I'm taking this one to the grave.