small stone first issue

[michael_krell]

does anyone know where I can find a small stone schematic. I need one for the first issue. The one that has 6 IC's instead of 5. I know its around because I have seen it before. It would be great  thanks

[jmasciswannabe]

I would like to second that as well! I recently acquired a six ic small stone on trade. It's a little more difficult to do some of the mods. I did the resistor lift vibrato mod, its the 27k under the big hulking blue capacitor. I am now trying to figure out how to cure the volume drop. Let me know if you find any info out on this michael and  I will do the same!

Ian

[michael_krell]

actually do you think i could get a picture of the inards of yours that shows where the wires go to? mine came all butchered apart and i just need to see where the wires go

[puretube]

m_k: you were quite close in august last year:
http://diystompboxes.com/sboxforum/viewtopic.php?t=23795&postdays=0&postorder=asc&highlight=2+ota+lfo&start=15
:wink:
now it`s here:
http://photobucket.com/albums/v324/caseyseffectpage/Flangers%20%20Chorus%20%20Phasers/?action=view¤t=ehsmallstone.jpg

[michael_krell]

Hey thanks man That schematic is wonderfull. I actually got that last one working. Once I get this one put back together I might have some more questions.

[michael_krell]

I have a question about this small stone. The circuit does not seem to be sweeping but my question is regarding the LFO. is this LFO powered by current? i know the never small stones ive worked with have all run off current and i checked it by checking the voltage across the 100 ohm resistor. Let me Know

[puretube]

on pin6 of A6 you should see a wave of ~4to5V amplitude (depending on the "color"-switch setting), floating ~1V above gnd.
The shape is that of consequent "M*c D*nalds"-signs turned upside down;
the 10k to the right of A6`s output turns this LFO voltage into the IABC-current flowing into pins5 of the shiftstages.

(Ohm`s law: I=U/R)

[michael_krell]

I measured the voltage at the point you described and im getting some strange things. When the rate knob is all the way down I get a very very small amplitude wave oscilating very slowly. As i turn the knob up it stays relatively the same, but then at one point it jumps up and becomes a large amplitube "upside down mcdonalds" wave with a maximum frequency of 25Hz. This seems right, but when the knob is about half way it seems there is a point where it just drops down entirely.

Also when i try to play this through my amp I get no change in signal when I unplug the battery, this is really wierd. Tell me what you think. THANKS

[puretube]

maybe the pot is worn (concerning the LFO behaviour);
the 1µF going to Vcc is another possible suspect;

if the LFO worx at the fast rate, you should hear a distinct warble at this setting...

if you hear only dry (and it doesn`t change with or w/o battery),
there`s more trouble ahead...

if you hear the dry for some seconds after disconnecting the batt.,
and it starts to fade away after a little while, you know that the input circuit is OK; (the 2 transistors).

Do you have a scope at hand?

Does the sound change with color-switching?

Check all wires/solderjoints.

Can`t remember if mmosopotamus`s mod is done with this version,
but iirc, he had good pics on his site...

[michael_krell]

maybe the pot is worn (concerning the LFO behaviour);
the 1µF going to Vcc is another possible suspect;

if the LFO worx at the fast rate, you should hear a distinct warble at this setting...

if you hear only dry (and it doesn`t change with or w/o battery),
there`s more trouble ahead...

if you hear the dry for some seconds after disconnecting the batt.,
and it starts to fade away after a little while, you know that the input circuit is OK; (the 2 transistors).

Do you have a scope at hand?

Does the sound change with color-switching?

Check all wires/solderjoints.

Can`t remember if mmosopotamus`s mod is done with this version,
but iirc, he had good pics on his site...

The pot is working fine because i took it out and tested it and cleaned it and its working, the 1uF tantalumn could be a problem but im not going to take that out yet. For some reason in one color setting im getting output on all the IC's. WIth a sine wave inputtued im getting a distorted sine wave outputted on all the IC's however they arent "dancing" like they should. On the other color setting im getting pretty much nothing on the outputs of the IC's.

I changed all the crappy solid wires and all of the solder joints. let me know what you think...

[michael_krell]

Also I replaced the 2 input transistors and nothings changed

Should I just replace all the caps?

[puretube]

only the 1µ at collector 2nd trans., for a start...

[michael_krell]

I dont have a 1uF capacitor there I just have a jumper. should i put one in?

[michael_krell]

I dropped in a brand new 1uF cap and no difference at all.

[michael_krell]

After looking at the schematic for a while I noticed that the power circuit on the right doesnt really match mine. Im very confused by the way that it is drawn out, can someone explain this to me??

[puretube]

on the right? :?

[michael_krell]

Im sorry I meant on the Left

[michael_krell]

Does anyone understand this, I cant figure out the different between the ground and the -Vcc.

[puretube]

no wonder: there is none...
you`re right, there is some inconsistency in the drawing:

1.) the "B+" of the circuit is +VCC;
2.) the "ground" of the circuit is -VCC;
    depicted as a circle, except at the 50µ CV smoothing cap,
    which has been drawn into the schem later...
3.) the "Vbias" aka "virtual ground" is generated by 2 resistors+cap
    top left in the schem (going to ground thru the input jack),
    depicted as a triangle, except at the minuspole of the big 500µF
    VCC load cap in the lower left schem: this should
    go to ground (-VCC), and not to Vbias.
    At this point, the triangle is wrong! (should be ground!).

Also the pluspole of the battery shouldn`t connect to +VCC
directly, but only to the switched lug on the 9V adapter jack.
(so it gets switched out of the circuit, when used with a wallwart.)
The minuspole goes to the upper node of the not-dimensioned voltagedivider-resistor & 10µF cap top left at the input-jack switched lug.

never trust a schematic on the web!  :lol:

[michael_krell]

Ok I kind of understand what you saying. Where does the minus of the battery connect to? I have it on the other switched lug of the input jack.