Thomas Henry's SN76477 Super Controller Module

Dan Lavin · Posted: Wed Jun 27, 2007 5:42 pm Post subject:

Fonik:
Well, I had to dig out my old college text books concerning JFETs like the MPF102. When the gate is shown in the middle of the line, it implies that yes the drain and source can be interchanged, but not all JFETs are. I will be honest and admit that I'm not sure about the MPF102, so you may be safe. Go ahead and change the other NPN X-sistors and if you still aren't 100%, try swapping the JFET's around....unless some other enlightened soul reading this can provide some illumination?

bugbrand · Posted: Thu Jun 28, 2007 2:58 am Post subject:

Yeah I've been confused a bit by jfets before too...

Checking out the MPF102 datasheet - the gate is pin3, which suggests it'd only happily go in in one particular orientation. I think the 2n3819 has the gate in the middle (pin2) so is more rotatable.. (then there's also the confusion of id'ing which pin is pin3 --- different datasheets list things differently, so I've always spent a while noting down variants and head-scratching when building in jfets)

fonik · Posted: Thu Jun 28, 2007 3:37 am Post subject:

fonik · Posted: Thu Jun 28, 2007 3:44 am Post subject:

halt!
no cause to blame myself this time. i did use the correct footprint for the MPF102 so they are orientated in the right way.
pin3 is ground, that's it.
for the schematic it does not matter if you interchange drain and source, i still assume.

Randaleem · Joined: May 17, 2007 Posts: 456 Location: Northern CA, USA

Hi,

Took a bit of digging, but:

http://www.du.edu/~etuttle/electron/elect25.htm

Third paragraph. It was buggin' me cuz we used to use a lot of these in old PAIA designs (Gnome, 2700 synth) and I know that we could put 'em in either way.

Back then (early 70's) the MPF102 was still sold as a unijunction transistor. With b1,b2 and gate for pinout.

But everything I was seeing just now was saying N-channel fet. This paragraph perhaps explains it...

BTW, here's another interesting link semi-related. But perhaps VERY useful to us in SDIY; considering the things said in this thread Smile

http://www.io.com/~n5fc/m3_sa.htm

Go to the the line just above the fifth picture. Which is the fourth set of three readouts. But IMO good reading all.

Randal

fonik · Posted: Thu Jun 28, 2007 5:54 am Post subject:

thanks for the links, randal.

when i understood it right thomas used the MPF102's in a switch configuration (in two slightly different ways, but still switches) so drain and source could be interchanged. somehow this way (www.elektronik-kompendium.de - analog discrete switches):
Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

this one really shakes me:

bugbrand · Posted: Thu Jun 28, 2007 8:14 am Post subject:

Dan Lavin · Posted: Thu Jun 28, 2007 8:45 am Post subject:

Fonik and troops,
I had some down time this am and finished checking the board layout. Here's my summary:
1. NPN transistors Q1, Q2, Q4 and Q5 are flipped 180 degrees (Q3 is fine)
2. Q7 is flipped 180 degrees (assuming pinout below)
3. Since drain/source are assumed to be interchangeable, Q6 is fine
4. Fairchild pin out for the MPF102 is
Pin 1 = Drain
Pin 2 = Source
Pin 3 = Gate
5. I could not find a "W" wiring post for the S/A input into A7. If it's not there, we can always tack onto the A7 side of the grounding resistor. Not a big deal.
Other than that, I have verified all components on TH's book against your pcb and everything looks very good. Less mistakes than I usually have!

fonik · Posted: Thu Jun 28, 2007 9:23 am Post subject:

hey antman, great work, thank you very much.

Dan Lavin · Posted: Thu Jun 28, 2007 10:50 am Post subject:

Fonik,

Dan Lavin · Posted: Thu Jun 28, 2007 11:45 am Post subject:

Fonik,

I got your email with the updated pcb layout and everything looks good. Thanks for the copy! I freaked out a little bit when I saw you moved Q3 and Q6 but you just cleaned up the layout a little bit. Also, I noticed caps C1, c13, c14, c15 moved as well. I'm guessing c13, c14, c15 were a little crowded on your prototype board as well as c1 perhaps. No big deal, it does look better.

Please go ahead and verify everything works with what you have now and if no problems, I'd recommend going ahead and ordering up your latest revision board with your board service. You've done an excellent job! Thanks from everyone here on the forum, I'm sure!

ringer · Joined: Feb 20, 2007 Posts: 49 Location: montreal

Hi Fonik,

I asked in a private email if the rate of the lfo will be voltage controllable.

Will this function be added to circuit? thanks.

Cheers,
R

v-un-v · Posted: Thu Jun 28, 2007 1:10 pm Post subject:

fonik · Posted: Thu Jun 28, 2007 2:16 pm Post subject:

fonik · Posted: Thu Jun 28, 2007 2:23 pm Post subject:

Dan Lavin · Posted: Fri Jun 29, 2007 6:02 am Post subject:

Fonik,
The LFO portion is relatively simple, so I would guess that the problem should be something obvious such as the setting of S4 or the gate in W5 not normalled to +5V. If that isn't the problem, start by verifying an output at pin 21 of the SN76477, then trace through U6, then U5. I'm sure you'll be running in no time.

bubblechamber · Posted: Sun Jul 01, 2007 5:57 pm Post subject:

I heard back from a chip broker and the best he can do is $12 each. it seems like a lot of potential hassle for a $3 savings over arcadechips. better luck next time.
david

Dan Lavin · Posted: Mon Jul 02, 2007 9:22 am Post subject:

Thomas,

If you're out there, Fonik and I require your assistance to verify something. I tried PM'ing you but either I'm an idiot or this forum will not let me PM you and I'm still an idiot.

Anyway, the BABMS and Sep/Oct 1981 Polyphony schematics are at odds with each other concerning Q1. The book shows the base of Q1 tied to +5V via 2.2K resistor and the status LED. The input S4 is tied to Q1's base via the 33K resistor. Fonik's pcb is currently like the book.

In Polyphony, Q1's base is tied to +5V via the 33K, then the 2.2K, then the LED with the S4 input at the 33K/2.2K resistor junction. This makes more sense to us as Q1 is always staying on for Fonik's book pcb regardless of whether ground or +5V is applied and Q1 is always on, grounding the SN's timing cap pin.

Can you verify the Q1 schematic in Polyphony is correct and the book is mis-printed? The circuit description in the book also seems to back up the Polyphony version. Thanks for your help!

fonik · Posted: Mon Jul 02, 2007 10:14 am Post subject:

one step forward: i changed my prototype according the polyphony article and now EVERYTHING works! great! thank you thomas henry, thank you antman!

i think we can close the case. i will update the PCB layout and on thursday i will post same samples...

Thomas Henry · Posted: Mon Jul 02, 2007 2:34 pm Post subject:

Hello Fonik and Antman,

You guys win the prize. I never noticed that before.

In fact, the Polyphony schematic is correct and the book schematic has a blunder in it. As you note, the verbal description only makes sense with the magazine version.

In case you're wondering how that happened, the publisher redrew all of my schematics (which by the way took me several hundred hours to do in the first place!)

Onward and upward,

Thomas Henry

fonik · Posted: Thu Jul 05, 2007 4:30 am Post subject:

so here is the final version. as you might want to recognize: i added standard MTA.100 footprints for almost all potentiometers, switches and jack sockets. (EDIT 06JUL07: now all oriented according tim's suggestions) the boards size is 4.7 x 3.3 inch (120 x 84 mm). i will post some sound samples later this day.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

philpeery · Joined: Nov 08, 2006 Posts: 137 Location: new jersey, usa

This looks really nice, Fonik! Any estimate on when it will be available for purchase?

Regards,
Phil

fonik · Posted: Thu Jul 05, 2007 5:58 am Post subject:

boards will be available in august. all who placed an advance-order will get a PM then.
if you changed your mind PM me to cancel your advance-order, please.

prices:
PCB 18.-USD/13EUR
S&H 7.-USD worldwide/3EUR europe

i still take advance orders until 12 JUL 2007, 10:00 UTC.

prophei · Posted: Thu Jul 05, 2007 9:56 am Post subject:

i'm in for one!