If 6 was 9 trace in progress. I have a gen question.

[brazdj]

Hello All,

I am working on reverse engineering my BC183 if 6 was 9 fuzz pedal.  It is a first time effort on my end and I have run into a peculiarity.  On my first trace through the circuit I ran across two components that have one connection to nothing... For example, I look at pot B100K Pin 1 which connects to a 1M resistor which then connects to the board and nothing else, all of its traces lead to no further connections.  As far as my novice eyes could see at least.   

This leads me to the following question:  can components on a PCB need not be attached directly to ground for them to be "grounded"?

I will run through my traces over and over before I post my findings.  But I plan to post gut shots, traces, parts list, diode voltage drop since I can't tell what 1N4... it is, and a schematic once I get this grounding thing sorted.

Oh! to all the newbies in the same boat as I.  In order to see traces underneath soldered pots, place a flashlight (smart phone flashlight works well) faceup on a table and rotate the PCB over the light, the traces show up reaaallll sharp.

Thanks,
Daniel

[antonis]

can components on a PCB need not be attached directly to ground for them to be "grounded"?

As you might know, "ground" is the most relative term in electronics world.. 
(e.g. a point  of 1V in a circuit working under 100 Volts could safely be considered as "ground", hence a point of 0.1V could be considered as "grounder" and a point of 0.000001V could be considered as "groundest" - in case of ground use as an adjective is appropriate..    )

"Indirect" connection of an item to a ground point (with absolutely zero voltage, if such a point could exist..  ) is interlaced with the connecting conduit (actully with it's resistance/impedance) and the current flowing through it..
(i.e. a node connected to ground via a resistor - or a capacitor in case of AC(*) - could be considered as ground itself in case of no current flowing through the resistor - the same stands for any other arbitrary voltage..)

(*) A common Emitter amplifier with Emitter degenaration is an example of the way we can ground a resistor in AC whereas is always there for DC..


P.S.
We could easily expand your query up to the forum server data handling capacity but forum administrators are really good guys so let's leave them in their peace of mind and shake hands for the following:
"Any object interjected between two points under no voltage difference is useless"

[duck_arse]

further to what antonis says, if a pot, trim- or panel-, has one of the end lugs (CW or CCW) "connected to nothing", the potentiometer is instead working as a variable resistor, or rheostat. [antonis will fix me on the greek if my spellink is rong, too.]

and, if the pot has one of its end lugs connected to the wiper, directly, via a short, the pot is another variable resistor.

a point to note on your BC18whatsis, they often come as an "L" suffix package, which has a pinout wrinkle - your datasheets will make this clear. in any case, why not post some pics for us to look at, one of those backlit board ones, for eg? why not, huh, why?

[brazdj]

Thank you both for the quick replies and the new knowledge.  At the end of the day, I will just draw those "not connected" ends as ground in my eventual schematic.

I'll post some gut shots, my tracings, components list, and data this evening if I get some spare time.  Eventually I'll post a schematic that I hope will get torn into by the relative experts on this forum...sometimes it is best to jump into the deep end!

Thank you again,
Daniel

[antonis]

I will just draw those "not connected" ends as ground in my eventual schematic.

Don't do it plz unless you've already drawn the schematic "as it is"...

@ Stephen: I'm impressed of your Greek spelling...!!! :beer:  :beer:  :beer:

[brazdj]

As mentioned.  Orange is component side, blue is pot side.  Pot numbering is based on left to right with knob facing me and lugs pointing down or south or towards me when looking down at the pot rating.

You can note on my attempted schematic that are two compenents with their ends not connected to anything but the pcb.  This was my first schematic so I didn't make too concerted an effort of ironing out all the input output or grounding details.

[antonis]

As far as I can see, your schematic (last diagram) isn't correct.. 

Taking in mind R6 placing, it should be connected to OUT (maybe via a decoupling cap..) but what's puzzling me is the sole diode facing to the +9V..
(it should result in a very heavy asymmetrical clipping - unless it's a reverse polarity protection diode which is wrongly drawn by you..)

As for D1, I can't trace anything..

BUT there isn't any DC bias path drawn for Q1 & Q2 Emitter to GND..
NFB from Q2 to Q1 makes also no sense (at least without a GND on the left of R5/C3 WITHOUT connection between them and Q1 base - or at least with a big resistor)
Negative FB from Q2 Emitter to Q1 Emitter is turn to Positive FB from Q1 Emitter to Q1 Base according to your scheme..
(I'm pretty sure that shouldn't happen..)

To make long story short, your diagram doesn't correspond to a "healthy" circuit.. 

edit: I'm pretty sure Stephen will come and slap my hands by reason of trace trial on a diaram with no In/Out/GND clear connections.. 

[brazdj]

Thanks Antonis.  Right now it is difficult for me to determine how the in out and grnd all link up.  If you look at my diagram or traces I sort of just point to where certain traces connect to either the input jack, output jack, and spdt foot switch.

I'm pretty confident in the traces I provided and the component list.  Though for the diode, I agree that it seems strangely placed.  Is there a way I can perform some test to zero in on this?  Note that when I used the diode/continuity setting on my DMM it read out 650.

I'll try the schematic again once I get a better understanding of it... I'll also use a silicon fuzz face schematic as a basis.

As for R6, how do I represent on the schematic that is "not connected"

Thank you again for your time.

[duck_arse]

antonis - slap slap, glub glub glub.

brazdj - my eyes hurt, so I'm not squinting at things too closely at the mo. I was going to suggest using the silicon fuzzface (well, any fuzzface, really, but with B-C caps added) circuit as a starting point, and try and fit your parts into it. but you beat me to it. it will help, tho.

as for board points not connecting to anything, is there a chance they are board "vias"? where a trace on top connects thru to a trace on the bottom? are your transistors "L" suffix or not? and for metering, for voltage, just connect your black lead to ground, and probe around with the red. all your voltages are then ground referenced. don't apply signal, tho, it doesn't interest or help us at this point. the voltages you read here will tell us 'things'.

for resistance or continuity, SWITCH OFF the power to the board, AWAYS. and then probe about as you like. one set of measures done w/ a lead on ground, and another set of measure w/ a lead on the V+ line will tell you some things about connections. caps will get in the way .....

one other thing, about pot pin names - head over to geofex.com, look for "the secret life of pots", and it will explain a few naming conventions that CAN'T GO WORNG.

[brazdj]

I have taken a more informed stab at the schematic using the above suggestions and some other research.  The spdt capacitor switching assembly has got me a hair confused if only bc the open throws end up having a stray capacitor end or a loose end period.  I looked at this thread for some info http://www.diystompboxes.com/smfforum/index.php?topic=118103.0

The BC183s have no Ls or any other post scripting, I measured their pins to make sure the layouts were correct on the schematic. 

If anyone has the time to review, please point out my errors!

[thermionix]

The spdt capacitor switching assembly has got me a hair confused if only bc the open throws end up having a stray capacitor end or a loose end period.

It's just C6 (trebly) or C6 + C10 in parallel (bassy).  The connection to lug 1 isn't necessary, could've been done with a SPST switch.

[Rob Strand]

A few comments:
- On your schematic R4 is missing.  Should go from collector Q1 to clean +rail.
- R1 should be 5.6k.  green blue red; 
   (6k6 is not a standard value, I thought 6k8 but when I looked at your pic I saw 5k6.)

I didn't check this piece by piece I only checked what looked strange.

[brazdj]

Thank you for the help/corrections.  Not sure how I missed R4...doh!

So when C10 is not engaged it has a floating end.  Is this just an outcome of this assembly method and not something to worry about?

[thermionix]

not something to worry about

[GGBB]

Pot pin numbers - CW is always 3, CCW is 1. You have the Vol and Bias pot pins labeled backwards.

[ElectricDruid]

As for R6, how do I represent on the schematic that is "not connected"

Marking pins or connections as "NC" for "Not connected" is the usual convention.

Tom

[brazdj]

Thank you again to everyone who offered up some time and advice.  I think I have gotten the schematic to a good point and my next step will be to just build it once I source the parts.

[brazdj]

Good Evening All.

I finally got all the parts and built the circuit based on the above schematic.  It worked out so I put together a vero layout and built it.  See below.  I am sure there are ways to make it more compact, but this a first time kinda job.

Hopefully someone is able to use and enjoy! (It is, as most could guess, a modified fuzz face with a "fat" switch).

Thank you for all of your help!

[brianq]

Thanx for tracing, I love me some fuzzface variants!!!


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