i'm stumped....tonebender attempt...

[pinkjimiphoton]

hi, tried building this:

.

it says unverified on the vero, but i believe in one of the threads cab42 said it was built and verified.

i tried building the one drawn by j.d. sleep, and went from long haired and frizzy to bald and frazzled. so i stripped the board, and started fresh.

i used the layout above, and subbed 5 parts...a pair of 1m resistors in parallel for the 470k, 2 2.7k's in series for the 5.6k, and a .047 cap to the right of q1. used a 10k from b+ to c of q2, it wasn't specified, i looked at a bunch of schems and it looked like the average. also used 6.8mf on the attack pot, as i was out of 4.7mf. used 5k as attack pot, out of 1k's.

using 2n4401  for q 1 & 2 nte123a for q 3.....supposed to be an ok sub for a 5088. hoping to use some ge npn nte103a for q1 & 2 if i can sort it out.

the layout etc seems wrong, the volume control needs to have the output from the board itself go to the wiper of the 100k pot, and output from pin 3. pin 1 is ground.

batt is a little weak at this point, b+ is 9.30


so....here's my debug info:

1.What does it do, not do, and sound like?

doesn't do anything but look pretty.

2.Name of the circuit =

tonebender mk II silicon version

3.Source of the circuit (URL of schematic or project) =

http://www.aronnelson.com/gallery/main.php/v/Cab42s-layouts/tbnpnsilayout.gif.html
this is the actual layout i used, i only used the one above to see the attack control wiring.

4.Any modifications to the circuit? Y or N

yes...please see above

5.Any parts substitutions? If yes, list them.

subbed 5 parts...a pair of 1m resistors in parallel for the 470k, 2 2.7k's in series for the 5.6k, and a .047 cap to the right of q1. used a 10k from b+ to c of q2, it wasn't specified, i looked at a bunch of schems and it looked like the average. also used 6.8mf on the attack pot, as i was out of 4.7mf. used 5k as attack pot, out of 1k's.

6.Positive ground to negative ground conversion? Y or N

unknown.

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>

9.30v

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:


Voltage at the circuit board end of the red battery lead =
note: i have checked continuity and for shorts, the ONLY way i'm able to get ANY b+ is to clip the lead directly to the - bat terminal...weird. continuity checks out for my connections, jacks aren't shorted...

anyways, = read 9.30 v where it connects to the board.



Voltage at the circuit board end of the black battery lead =

0

transistors removed, reading at sockets:

Q1
C = 9.29
B = 9.21
E = 9,29

Q2
C= 9.29
B= 9.29
E= 0

Q3
C= 9.30
B= 9.29
E= 9.29

4.7 mf - =  weird, starts about 8v, then drops... + side 9.21v...have minus side facing input cap.

47mf + = 9.30, - = 9.21

output side of .1 mf = 9.21

input side from b+ = 9.30

attack pot all 3 pins read 9.29

volume pot

3 = 9.21
2 = 9.29
1 = 9.29

this is really freekin weird, cuz it's reading 9.29 v + at the ground plain on the bottom.

if i connect the - terminal of my dmm to output jack earth, i get ZERO  voltage, anywhere!!!!!!!!!!!!!!!!!!!!!!

BUT....if i connect the + lead of my dmm to the ground of the battery directly while it's hooked to the circuit via the batt snap, it now reads - 9.30 v!!

wtf...the batt isn't hot, nothing appears shorted,,,,

i am completely stumped!!

could it be a shorted electrolytic??

pix to follow...please help me figure this out, i'm a newbe and completely stumped!!!!!!

btw...what looks like a solder bridge in the middle is supposed to be there, according to the vero above, the junction of q1 c and the 10k resistor.









thanks folks!!!!!!!!!!!!!!!!!! 

[petemoore]

Q1
C = 9.29
B = 9.21
E = 9,29
 Although '2k7' is only a part of the equation which = emitter voltage...measuring from transistor lead to distant ground, there should be ~2k7. That all three are ~V+ voltage makes a mis-ground/cold solder, or misvalued resistor suspect, by reading an R value through as many 'should be connected' solderjoints/components, about 2k7 reading = checking many conenctions and R value.
 Q2
C= 9.29
B= 9.29
E= 0  
 Similar but test from collector lead through to battery pole or first V+ interrupt [if there's a power switch or anything else between Q1C bias resistor and V+. There should be about the shown value between Q1CR and battery+.
 Q3
C= 9.30
B= 9.29
E= 9.29
 Q2 and Q3 are parts in the second gain stage of the Tonebender, both transistors play a role in the feedback loop amplifier, that many 'near-toward-ground points in the circuit [emitters] are almost V+...test from ground to each point marked ground on the circuit...{the post looked to be very well written, but I skimmed parts of it.
  Alternately, test from V+: ?..is somehow V+ getting into a node other than it's node?
 With a circuit :
 V+
 10k
       > Should be nearish toward Gnd. Voltage in this circuit.
 2k7
 GND.
  It looks like something isn't pulling the voltage toward ground at all, much to big emitter resistors or coldsolder ?

[twabelljr]

transistors removed, reading at sockets:

I think you need to take these measurements with the transistors IN the sockets.

[petemoore]

  Whoops yes, that's whappens when skimming.
   

[pinkjimiphoton]

thanks pete,
i've re-checked the solder joints, and reheated any that are suspect ...all APPEAR to be ok!!!!!

this is almost exactly the prob i had with the first tonebender project, and why i abandoned it. i am stumped....completely.

i will check over the connections, and try and see if i can find any other issues. the only thing i can think of is the electrolytics? but the voltages seem to suggest they're ok, ie: they read higher on the + side....but the weird thing is how the + side of the 4.7u electrolytic shows voltage, which over time drops to 0v, could that maybe be from the .01u cap at the input of the circuit going to ground?

i've messed with electronics for a while now, never encountered anything so weird...usually, either it works out of the gate, or is a pretty easy debug.

checking resistor values on the board...

left to right, as things aren't labeled as r1, r2 etc....

1k reads 990

100r = 99.6r

100k (bottom left) =88.1 (climbs...weird..)

found 1 prob....the two 1m in parallel are reading 52k, rather than the 500k expected...both are labeled, so must be a glitch from the manufacturer?
from the bottom of the board tho, reads .085m

10k to q1c =  9.81

resistor from q1e to ground reading 2.14k

100r =99.1r

another prob...100k resistor just below q2 reading 4.8k!! mismarked!!!

10k from +rail = 9.6k

220r = 214r

1k = .995k

5.5k = 4.37...gotta replace that, too

so, three resistor values that are way off...could those be the culprits?

well, if nothing else, i've learned to measure stuff as i go!!!


still stumped...gonna go hit radio shack and get some more resistors real quick, try changing them out and the electrolytics, too.

am i correct orienting the 4.7 u cap with negative toward signal in?

thanks again for the help, i really appreciate it!!

[pinkjimiphoton]

with the transistors in the sockets, i get no b+ unless i connect the neg from my meter directly to the - pole of the 9v...

if i connect it to the circuit ground at any point, i get nothing!!!

if ya re-read my post, i think you'll see i mentioned that, and that i'm getting a NEGATIVE 9v reading from the - pole of the battery with the - lead from the meter connected to the - pole of the batt, and ZERO v from the positive....something is really screwed up!!!

be back shortly with more parts...thanks guys...

[petemoore]

  The resistors that are 'ballpark' are fine,
   The 500k that 'reads funny' could be having a circuit around the R...a path around the resistor [I understand 2x 1m paralleled to = 500k].
   For now, run more tests before changing resistors.
  meg resistors have last green band, for this debug, resistors rarely fall far enough out of specification to matter.
   Some wierd little thing that may rear it's head after you've dreampt...
  Soaking up some zzzz's and approaching it again when refreshed is recommended/seemed required sometimes..the letting go is what tells more about reforming the grip.
   Electronics always works in different ways the same way very consistantly, [choose phone/computer etc., invariably has to follow the 'rules'] whether the work is the way the human would choose it to be only matters when the circumstances are such'n such in the circuit. So there's some little thing in there..a bug...gotta be, just as when the bug is ferreted out it will have to work as expected.

[pinkjimiphoton]

sage advice, pete...

i am going to swap out the paralleled 1megs for a 470k, and replace the 5.5k with a 5.6k, too, while i'm at it...then i'm gonna walk away from it overnite i think, try looking at it with a fresh brain tomorrow.

thanks for all the help!!

[tiges_ tendres]

Three things
1) Are you measuring resistance with the resistors soldered in the board?  That will give you false readings as it measures the resistance of everything else connected to those resistors.

2) Did you notice what looks to be a little blue jumper on the layout at Q1's collector?

3) Be careful with the schematics you are referencing for your values.  There are germanium pnp versions of this circuit that have different resistor values than the npn silicon version.  10K doesnt sound right for the collector resistor on Q2

[pinkjimiphoton]

i didn't know that about the resistors! thanks, i've learned alot here from the folks on the forum!

looking at the schems gets a wee bit confusing to me after a while...so many versions, and not sure which is right...that's why i finally went with a silicon npn neg ground version.

i did notice the little blue jumper at q1's collector and added it under the board...maybe that's the problem? i didn't think it would really need to be above the board under the socket...

the 10k at q2 is indeed a bad guess on my part...it seems the average there is about 47k on most of the schems.

thanks for the feedback!!

also didn't know you're supposed to measure the voltage with the transistors in the socket...will try re-doing it with them installed and see what shakes out.

thanks!

[pinkjimiphoton]

replaced the resistors with ones that were closer than before...and swapped out the 10k at q1 c for 47k. reinspected for shorts, cold solder etc....same thing.

but NOW if i touch the casing for the volume pot, it sounds like i'm touching the end of a guitar cord. i took the pot off, checked it for shorts etc, it's not the pot. when i hooked it up, same thing. i DID switch the input to the volume to the wiper and the output from pin 3 to the hot of the output jack cuz i noticed the volume control didn't work on the buzz right...it kinda only worked around the middle of the pot, and then almost acted like a tone control when turned up.

another weird thing to add to the list is that with the transistors in, i get no b+ at all. if i read from - on the battery itself, i can get voltage readings...roughly 9.5 volts, everywhere.
if i take a voltage reading from battery - to the audio INPUT, it starts off reading about 9.30 volts....then drops slowly to 0 volts.

could this be a cap problem? shorted maybe? or could it be because i used electrolytics instead of non-polarized caps? i didn't think it would matter as long as the + of the caps was towards the higher + voltage...

the one good thing, i guess, is that now when i touch the end of a guitar cord plugged into the input, i can just barely hear a buzz...nothing like touching the casing of the volume pot tho.

stumped!!!!

[pinkjimiphoton]

this thing keeps getting weirder. it's like a gremlin or something. i've got q2 and 3 working...kinda...but now can't get b+ on q1!

taking a break...any help much appreciated!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[pinkjimiphoton]

ok, i've been messing with this thing for days now. it's still not right, i've checked, re-checked and re-checked again and again against numerous schematics and layouts, and have gotten nowhere at all. my biggest accomplishment so far seems to be that if i have it plugged into an amp, the negative battery lead, if disconnected from the board, will give a loud honk thru the amp.

too weird. spent all day trying to chase down where the voltage on q1 had dissappeared to, as it was reading .07 on the collector...the other two were reading about 4.6v at that point. now i've gotten power to the c on q1 again, by swapping out a 100r resistor to ground, and reading a good solid 9.4 v...but...now q2 and 3 are reading 8.4 or so.
tried using trim pots in various fashions with no effect...tieing pins 1 &2 together to try and use as a variable resistor, even tried using it as a voltage divider straight to ground with pin 3...same thing, no effect whatsoever.

i am beyond stumped. and about to abandon another project...not good, after 12 builds, the last 3 now are failures i can't figure out.

does anyone have a tonebender project that DOES work, that they've personally built using a neg ground silicon npn kind of circuit that is reasonably newbe friendly right outta the box?

i would really appreciate the help, thanks...

[petemoore]

  Did you check that the trace-cuts insulate?
   For instance the 100k's uncut trace would be a jumper.

[pinkjimiphoton]

yep. checked all the cuts, checked for continuity....it's good where it should be, and has none where it shouldn't.

beats me. this is the weirdest thing i've ever run into!

[PRR]

Are you still at this point?

> i get no b+ unless i connect the neg from my meter directly to the - pole of the 9v...

Neg side of battery must go where it's supposed to go, in this case probably the ground bus on the vero. In a pedal, this might be via a 3rd contact on a jack; you need a plug in the jack to make the connection.

> if i touch the casing for the volume pot, it sounds like i'm touching the end of a guitar cord.

This also suggests a missing ground connection.

[pinkjimiphoton]

i got it...there were a couple real weird things happening. i actually abandoned this a day or two ago, and re-breadboarded the circuit. worked like a champ.
so i transfered to vero, found one problem...i'd forgotten to cut a trace between q2 and q3....

and the other prob was i had cheezed out and made a 9v clip outta a dead 9volt. it was acting like a huge cap, for some reason...changed it out, probs went away!!

anyways, will up the finished project in a new thread. thanks for all the help guys!!!

really appreciated!!