Debugging help for String Ringer v1.3 needed!!!!!

[njkmonty]

I have completed The string ringer v 1.3, but think i have voltage problems

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47423

My build includes the Use of VTL5C3 Vactrols, incorprating the 5K trim and 680ohm R39
My Transistors, bc549c come from smallbear

I have bypassed the LFO Depth Jack, by connecting the purple lead to the grey lead (on the jack)
and simply left the VCO wires unconnected.
all the pots appear to work, however
the optional "rate" indicator doesnt work and the led connect to r39 (680 ohm) doesnt work!!!
BUT...
when i connect a led and limiting resistor connecting to the purple wire ( (just below the rate pot)  the "optional  rate indicator  then flashes as it should and can be adjusted with the rate pot
when playing guitar the lfo led coming off R39 begins to respond to strumming. the only problem is the sound doesnt sound right.
my thoughts are that the extra led is reducing the voltage to a more operating level but not ideal

Vref 1  (where R7 & R8 meet measures 3.495 v

Voltages
input voltages 8.95v
IC 1 (TL074)

1  3.5v
2  3.5v
3  3.5v
4  8.2v
5  4.1v
6  4.1v
7  4.1v
8  3.5v
9  3.5v
10  2.7v
11  ground
12  3.4v
13  3.5v
14  3.5v

IC 2 (TL074)

1  8.0v
2  6.8v
3  7.5v
4  8.95v
5  7.4v
6  8.2v
7  1.4v
8  8.0v
9  6.7v
10  7.5v
11  ground
12  7.5v
13  7.5v
14  7.5v

IC 3 (TL074)

1  7.4v
2  7.5v
3  7.9v
4  8.95v
5  230 millivolts
6  7.5v
7  7.5v
8  1.8v
9  7.5v
10  6.3v
11  ground
12  7.5v
13  3.8v
14  8.3v

IC 4 (Ne5532)

1  3.5v
2  3.5v
3  3.5v
4  ground
5  1.5v
6  1.5v
7  1.2v
8  8.2v

Transistor 1 BC549C
C    7.3v
B    8.0v
E    7.3v

Transistor 2 BC549C
C    8.9v
B    7.5v
E    7.5v

Transistor 3 BC549C
C    8.4v
B    7.3v
E    6.8v

Transistor 4 BC549C
C    6.8v
B    7.5v
E    6.8v

Transistor 5 BC549C
C    8.0v
B    1.4v
E    6.8v

[slacker]

Something is wrong with your Vref2, pins 5, 6 and 7 of IC3 should all be about half the supply voltage. I'd start checking round there, remove IC3 and measure the voltage at the junction of R29 and R30 you should get half the supply, if not check for a wrong component value, a bad connection or a short to ground.

[digi2t]

Don't forget to ensure that your LFO Depth jack should not be grounded to the circuit in any way. This will kill your LFO. Problem I've seen with a couple of builds where people forgot to use insulating washers (or insulated jacks) when mounting the jack into the enclosure.

[njkmonty]

will do that now, but one quick question,
on the scehmatic top left is the power component,
i can see Vref 1, V+, V+1,,, but where does Vref2 originate from?
i can see it at various llocations around schematic but where is its origin?

[slacker]

Bottom left of the schematic, R29 and R30 make a voltage divider to get half the supply, this is then buffered by IC3/2.

[njkmonty]

"emove IC3 and measure the voltage at the junction of R29 and R30 you should get half the supply"

with ic3 removed i get 8.95V!

[slacker]

There's your problem then Check all the connections to R29 and R30 and make sure J13 is connected to ground. Also check to see if you have anything shorting pin 5 of IC3 to pin 4.

[njkmonty]

i reslodered the joint and it appears to be voltage dividing properly now, replaced all tl074 just in case
leds etc working as suppose to plugged it in appears to be working, thanks, but volume and blend pot behaving a little strange
will post new voltages

[njkmonty]

New voltages
Voltages
input voltages 8.95v
IC 1 (TL074)

1  3.9v
2  3.9v
3  3.9v
4  8.12v
5  4.1v
6  4.1v
7  4.1v
8  3.9v
9  3.9v
10  3.1v
11  ground
12  3.8v
13  3.9v
14  3.9v

IC 2 (TL074)

1  4.4v
2  4.4v
3  4.4v
4  8.95v
5  4.1v
6  6.7v
7  1.4v
8  7.4v
9  4.4v
10  4.4v
11  ground
12  4.4v
13  4.4v
14  4.4v

IC 3 (TL074)

1  4.5v
2  4.4v
3  4.4v
4  8.95v
5  4.4v
6  4.4v
7  4.4v
8  4.4v
9  4.4v
10  4.5v
11  ground
12  4.4v
13  4.4v
14  4.4v

IC 4 (Ne5532)

1  3.9v
2  3.9v
3  3.9v
4  ground
5  3.4v
6  3.4v
7  530millivolts when volume on full, 1.7v when volume on zero  ?
8  8.1v

Transistor 1 BC549C
C    6.7v
B    7.4v
E    6.7v

Transistor 2 BC549C
C    4.4v
B    5.1v
E    4.4v

Transistor 3 BC549C
C    4.9v
B    4.6v
E    4.0v

Transistor 4 BC549C
C    4.4v
B    4.4v
E    4.0v

Transistor 5 BC549C
C    4.4v
B    5.0v
E    4.4v

[njkmonty]

i think ive got it working, it does all sorts of weird stuff!
the only initial thing is ive found the blend and volume potentiometers behave differently to conventionally blends and volume?
the volume on some settings appear greater when volume is at its minimum and blend is full clockwise, when i turn blend back down to hear the raw guitar it appears to be a lot quieter when some of the highs rolled off?
what are others experiences with these pots?

[LaceSensor]

volume was an extra addition
its useless. It goes from unity to crazy loud. I always keep it totally backed off.

Blend should mix in your straight signal with the ring-mod'd signal.
it should sound just like your straight sound in bypass when you have blend fully counter-clockwise

good luck

[slacker]

You've got some sort of problem with IC4, pin 7 should be about the same voltage as pins 5 and 6 and it shouldn't change with different volume pot positions.

[LaceSensor]

There is a resistor in the build doc that says between 100k and 1m

What value did you use?

[njkmonty]

ok , I feel that im close...
I connected my guitar lead from my amp, to the "Blend" pot
apparently the original doesnt have a volume pot.
now when i connected the guitar lead to lug 1 of "Blend" Pot i get full clean dry  signal
and  on lug 3 a full wet signal
when i connect the guitar lead to the middle of the blend pot, it appears to have the right volume when blending it from dry to wet on the pot.
Now from the middle lug on wards things start to go a little funny.

my updated voltages for IC 4 ( NE5532) are

1) 4.35v
2) 4.35v
3) 4.35v
4) ground
5) 5.9v
6) 5.9v
7) 7.08v
8.1v

now Ive swapped over NE5532  with several others just incase its stuffed, but from what I understand pins 5,6,7 need to be all the same?



"There is a resistor in the build doc that says between 100k and 1m"

What value did you use?
i think i used 1m resistor

[LaceSensor]

Try 100k... Might not fix your issue but it's what I use there and mine are sounding legit....

[njkmonty]

will give it a go , do you think that that could have an effect on pin 7 of IC4?

changed the 1Meg resistor to 100K , it made no difference to the IC4 voltages
Isnt R64 mainly for polarity protection?

ive swapped over heaps of NE5532, even tried lm833  no change, Im getting a little  
my updated voltages for IC 4 ( NE5532) are

5) 5.9v
6) 5.9v
7) 7.08v

also did you find your trim pot on the transformers baby board did much for you?  


Ive been stuffing around with this for past couple of hours, resoldering the ic4 post blend section removing caps and resistors and remeasuring and no change.

so i noticed the original version by Lovetone never even had a volume pot. and ended with 460 ohm resisto/10uf cap/22k to ground
so i searched around and found this...


i aligator clipped the centre lug of my blend pot and connected it to a breadboard with a 100K log pot  and the 2 resistors and electrolytic.
it seemed to work great and the voulme worked just like a volume normally does.
is there a reason not to do this, and if not why didnt anyone do this before?

[njkmonty]

anyone???

[njkmonty]

PPLLLEEEAASSEE?!!!!!!

[slacker]

Do the same as for your other problem, remove the opamp and then measure the voltages on pins 5, 6 and 7 of the socket.  You should get about vref1 on all of them. If not check for wrong components, dodgy connections or shorts.