EHX - Deluxe Octave Multiplexer Schematic Redraw

[Scruffie]

This was a big one, it'd be handy if anyone could cast an eye over it to check for any mistakes I might have made and haven't spotted 

Source Thanks to Nelson:- http://sites.google.com/site/electroconducive/EHXDeluxeOctaveMultiplexer-Factory.jpg
(Thanks to Stephen Giles too)



I left off the power supply for now... it's clear enough for anyone wanting to do a repair on the factory schematic and I doubt any DIYer is going to bother finding the correct transformer if they build this.

Processaurus posted some gut shots of his unit up in this thread aswell - http://www.diystompboxes.com/smfforum/index.php?topic=87905.0

[nelson]

Good job!

Best way to be sure of errors is to print a copy of the factory and original and get the highlighter out. checking nodes and component values.

[Scruffie]

Good job!

Best way to be sure of errors is to print a copy of the factory and original and get the highlighter out. checking nodes and component values.

Cheers! 

No Printer to hand at the moment but when I get one back in a couple of weeks, i'll give that a go unless someone spots something before, it looks pretty okay to me though... but I wont say 100% just yet.

Now... converting this to LM13X00s and a Charge Pump to give that Bi-Polar Supply...   

[nelson]

Good job!

Best way to be sure of errors is to print a copy of the factory and original and get the highlighter out. checking nodes and component values.

Cheers! 

No Printer to hand at the moment but when I get one back in a couple of weeks, i'll give that a go unless someone spots something before, it looks pretty okay to me though... but I wont say 100% just yet.

Now... converting this to LM13X00s and a Charge Pump to give that Bi-Polar Supply...   

Charge pump is fairly straight forward, the LT1054 can supply up to 50ma single or 100ma in parallel.

Switching out the 3094's for LM13700's? That's a bit above my pay grade. If I was to start investigating it, I'd note the different current requirements of the chips, one having their Iabc pin one diode drop and the other two diode drops above V- and work from there. The 3080 is essentially a 3094 without a buffer, so you could use that and a darlington buffer as in the small stone clones around. You could also look at the LM13X00 based Ross/MXR compressor clones around and see how they modify the external circuitry to incorporate that IC instead of the 3080. Then, simulate/breadboard. 

All in all it does seem like a lot of work for posterity. I really doubt many people would build this.

[StephenGiles]

Another work of art - well done as our dentist always says! I never understood what the note above the LM311 meant. Just a reminder that the top section up to the fundamental generating adaptive filter forms the front end of the rackmount guitar synth

[Scruffie]

Good job!

Best way to be sure of errors is to print a copy of the factory and original and get the highlighter out. checking nodes and component values.

Cheers! 

No Printer to hand at the moment but when I get one back in a couple of weeks, i'll give that a go unless someone spots something before, it looks pretty okay to me though... but I wont say 100% just yet.

Now... converting this to LM13X00s and a Charge Pump to give that Bi-Polar Supply...   

Charge pump is fairly straight forward, the LT1054 can supply up to 50ma single or 100ma in parallel.

Switching out the 3094's for LM13700's? That's a bit above my pay grade. If I was to start investigating it, I'd note the different current requirements of the chips, one having their Iabc pin one diode drop and the other two diode drops above V- and work from there. The 3080 is essentially a 3094 without a buffer, so you could use that and a darlington buffer as in the small stone clones around. You could also look at the LM13X00 based Ross/MXR compressor clones around and see how they modify the external circuitry to incorporate that IC instead of the 3080. Then, simulate/breadboard. 

All in all it does seem like a lot of work for posterity. I really doubt many people would build this.

Yes but making the Charge Pump deliver 12V Bipolar from a 9V supply... I know i've seen how to do it before, just can't remember where...

Well I would say convert to 3080s and infact that's what i'd much rather do but they're more scarce i'm led to beleive and doesn't the LM13X00 contain two OTAs with Darlington Pairs already? So that cuts down the chip and extra transistor count a bit. Then is there any reason we couldn't make U1 & U4 a Quad Opamp to save a bit more room?

It is mainly posterity but when I posted about reviving pedals with PCB runs, this one did get a bit of interest, so I wonder if fabbed PCBs might change some minds on the matter of building it, only a small batch but still... i'm mainly considering it for now but if I could get the project reworked to available parts, that'd be a big push in the right direction.

Another work of art - well done as our dentist always says! I never understood what the note above the LM311 meant. Just a reminder that the top section up to the fundamental generating adaptive filter forms the front end of the rackmount guitar synth

Cheers  I think that's quite enough redrawing for the moment...
It's just telling you to connect it to Pin 6 of the other 311 isn't it? Or are you referring to why it says 'Mute' Can't say i'd know.

[StephenGiles]

So it is, I'never noticed that other mute note before!!!

[Scruffie]

I've been going through Processaurus' Gut shots filling in the Part values on the images before I take my first stab at tracing something (Start small eh?) and I have a sneaking suspicion that the schematic may well be correct, the values all seem to actually match up which for EHX   and everything seems to be where it should be... i'll post the updated picture with values when i'm done with it (Hope you're okay with this Processaurus   ).

This is where i'm at (A few values might be questionable, but it was the best I could make out):

(Darkened to show up resistor values)

If the schematic is to beleived the Two Transistors to the Top Left should be 2N5087 (Not sure what the big thing behind them is?) and the Two down the Right hand side should be 2N4302.

The Far Left side is Power Supply so i'm ignoring that for now.

[DiscoVlad]

If that's the power supply part of the board, it looks like a fuse.... though looking at the factory schem, it's more likely to be a bridge rectifier.

[Scruffie]

Here's my Interpretation of the PCB For this from Proccessaurus' Gut Shots, i'm 98% sure of it... it probably has one or two small errors but it's a start atleast.

Just to mention, on the schematic there's a connection missing from Pin 7 or U11 (311) to Pin 3 of 13 (4013).

[HarryBBD]

Hi

you are missing the connection from the LM311 to the 4013 pin 3

I'll see if I can find any more errors...

I'm playing with a simualtion of this circuit in LTspice.  One thing I'm trying is to add a second filter stage to get a more stable waveform out. It looks like it might be possible.

BBD

[Scruffie]

Hi

you are missing the connection from the LM311 to the 4013 pin 3

I'll see if I can find any more errors...

I'm playing with a simualtion of this circuit in LTspice.  One thing I'm trying is to add a second filter stage to get a more stable waveform out. It looks like it might be possible.

BBD

Hey,

Yeah I mentioned this in the post above   not very clear though i'll admit, at some point i'll update the schematic to include that, I haven't found any other errors.

You're trying to make this more complex!?    

There's another thread on here by Processaurus which show the waveforms of his actual unit, might be of interest.

Edit: Here's the thread - http://www.diystompboxes.com/smfforum/index.php?topic=52725.0

[liquids]

Should pin 8 of U10 really connect to ground?

I'm trying to sketch up the tracking filter for LM13x00 adaptation, but man this schematic is hard to follow (even when more clearly drawn, as yours is)!

[liquids]

And for that matter, does pin 8 connect to the other three components that cross it?  It has no 'arc' to show not connected, nor a 'dot' to show connection.

[Scruffie]

It's hard to tell on the original but i've drawn it how it looked... can't really help you i'm afraid, best bet would be to compare the schematic to the PCB trace.

[StephenGiles]

Should pin 8 of U10 really connect to ground?

I'm trying to sketch up the tracking filter for LM13x00 adaptation, but man this schematic is hard to follow (even when more clearly drawn, as yours is)!

It's not connected to ground.

[Gurner]

As I look at that circuit....it takes my breath away & screams low parts count mcu! 

[slacker]

Cool, do it then and share it with us

[liquids]

It's hard to tell on the original but i've drawn it how it looked... can't really help you i'm afraid, best bet would be to compare the schematic to the PCB trace.

Thanks for your work Scruffie.  It's really appreciated.

I'm doing just that at this point...I just realized I didn't have the most recent/clean PCB/traces image which I now see above...and that...uh...seems to make a difference.    

[beatnik]

has scruffie's pcb been tested by someone? looking forward to build this