D*A*M - Gravity Isolator

[beedotman]

Yo!

Here's another beautiful D.Main work - Gravity Isolator. Fleshhead son.
It's MKII circuit with fixed fuzz and tone section on the output similar to MKIII.

Electro input and fuzz caps are not confirmed, I just followed values used in Fleshhead.
Same thing for output caps - yellow one is smaller than 100nF so it propably has smaller value - that's why 47nF. 4,7nF fits nicely to it
Transistors are Mullard OC82DM.
Lot's on underboard jumpers shown on layout as white wires.

Enjoy!
b

[rocklander]

am I reading that picture correctly, they twist the centre pin of the 3pdt to be perpendicular to the other pins? or are there 3pdt with that already like that? if they do twist it, does that not reduce the electromechanical reliability? (I mean putting extra strain on it physically).

[beedotman]

I think that pin in center is just like others, it just looks twisted because of the wire and solder on top of it

[Intripped]

mmmh... that pin seems to be like the others, not twisted.


edit: just as Beedotman said

[rocklander]

oh so they've looped it over the top? ... fair nuff..

[mirosol]

I drew the schematic on the bottom tagboard layout file into stripboard (http://tagboardeffects.blogspot.fi/2013 ... lator.html), but myself and one reader are having problems. I'm pretty sure the layout matches the schematic, but probing tells me that the signal dies at Q1. Not an expert, but should there be something between the base and collector of Q1?

[beedotman]

Maybe wrong input cap polarity? IMO nothing is missing between Q1 base anc colector...
In regular MKII there's nothing as well.

[mirosol]

Signal is passed to Q1 base, but i'm not getting anything on the collector. Rest of the circuit seems to be working. If i short the base and collector with 10k resistor, it works, but sounds bad :) I've tried on a few different transistors, but no luck so far. Beats me, as it's really simple. 4µ7 to the base with 10k to ground, emitter grounded and collector gets -9V through 10k and it should pass the signal to 100n..
+m

[phibes]

There doesn't need to be a resistor from Q1's collector to base. Did you mess up the grounding anywhere with this being a positive ground circuit? One thing on your layout that screams at me right away is if you hook up a battery to your layout the way you got it drawn it won't work right. Black is negative, red is positive.

Bman, the transistors in your schematic are using the NPN symbols.

[beedotman]

Bman, the transistors in your schematic are using the NPN symbols.

I know, men... But when I choose PNP transistor in DIYC - emiter and colectors are upside down and I can't rotate them at all. So instead drawing ground at top and power rail at bottom - just used NPN... lesser evil

[beedotman]

Black is negative, red is positive.

Aye

[beedotman]

Signal is passed to Q1 base, but i'm not getting anything on the collector. Rest of the circuit seems to be working. If i short the base and collector with 10k resistor, it works, but sounds bad

It sounds like wrong transistor or maybe colector swapped with emiter, or transistor grounding?
If You are adding resistor between base and colector You simply bypassing singal around Q1.

[beedotman]

This is almost the same circuit like in MKII, just a change in output section and fixed fuzz.
Like here:

[beedotman]

BTW: one of those units (propably 6 ever made) are currently on ebay.

[phibes]

Dang Bman, coffee??

[mirosol]

One thing on your layout that screams at me right away is if you hook up a battery to your layout the way you got it drawn it won't work right. Black is negative, red is positive.

I bet we could discuss this for hours. The layout clearly says "-9V". Ground is never negative nor positive. It's always exactly 0 volts. I always draw my layouts with ground as a black wire, because - charge pump/voltage inverter.

I'm still fairly confident about the layout. Just haven't got around to play with it more.
+m

[phibes]

Alright, have fun.