Tremulous Bear Build Report and Need Help Troubleshooting.

[studiostud]

Hey guys,

I finished all the wiring for the tremulous bear tremolo pedal from smallbear.  Need some help with the troubleshooting now.  Thanks in advance for any ideas. 

Here's what I've got for now...

Name of Circuit: Tremulous Bear

Source: http://www.smallbearelec.com/Projects/TremBear/TremBear.html

What does it do/not do?
* LED indicator is not functional
* No sound in output.  All I get is a very faint buzz that does seemed to change when adjusting the level pot but never gets very loud. 
* No audible "sweeping" sound when adjusting the speed and depth pots.

Modifications to the circuit?  I have made no modifications to the original schematic.  I bought this as a kit and assembled per directions.

Parts Substitutions? None.  All parts necessary came with kit.

Positive/Negative Ground Circuit?  Negative Ground

Out Of Circuit Battery Voltage?  9.22V

With negative lead from dig multimeter on Ring tab of Input Jack (where black lead from battery connects) -
* Voltage at circuit board end of red battery lead:  9.20V
* Voltage at circuit board end of black battery lead: 0.0V


TRANSISTOR VOLTAGES:

IC 1: TL072P

1 - 0.0   5 - 5.45
2 - 0.01   6 - 0.01
3 - 8.73   7 - 0.01
4 - 8.73   8 - 8.74

IC 2: TS555CN

1 - 1.32   5 - 4.16
2 - 3.21   6 - 4.37
3 - 4.17   7 - 4.37
4 - 0.0   8 - 4.37


Q1: 2N7000

D - 0.01
G - 0.01
S - 0.01

Q2: 2N2222A

E - 0.57
B - 1.19
C - 0.58

Q3: MPSA14

E - 0.0
B - 0.08
C - 0.58


DIODE VOLTAGES:

D1: 1N914

A - 0.01
K - 0.01

D2: 1N914

A - 1.69
K - 1.19

D3: 1N4001

A - 9.20
K - 8.16


THINGS I FOUND ODD:

* Well first of all, my transistors are obviously pretty messed up.  I'm guessing the Q1 is bad, but I'm wondering if maybe it's another part of the circuit that's not getting voltage to it.  Same idea with D1.  I actually did a diode test on D1 and it tested fine. 

* The pedal seems to draw power from the battery unusually quick.  After maybe 15 min of testing, the battery has dropped around .2 or .3 volts.  Is this natural to be draining the battery this quick?  I would imagine in a live music setting, it would drain the pedal battery to death before the show was even over. 

* This is my first pad-2-pad PCB wiring job so I wouldn't be surprised if something is incorrect with the connections.  Everything seems to check out ok with the continuity test but that's also pending everything is connected to the right place.  Has anyone done this pedal and has a photo of their PCB wiring?

[QSQCaito]

There's something looking odd in almost every voltage. In the TL072 you should be getting something similar to(in most of the cases its like this, hope i'm not wrong)
1- 4.5
2- 4.5
3- 4.5
4- 0
5- 4.5
6- 4.5
7- 4.5
8- 9

You're getting 9v in pins 3 and 4 which should not be happening. I would check your power source, and specially for diode bridges, and cold solder joints. There's voltage where it shouldnt. Check your power supply area. Maybe you've got something between R20 and R22, If i'm not wrong you should be getting 4.5v from there.


Well. As you may see my knowledge is very limited. But I can tell that you're voltages are wayy wrong. I would check to see that you haven't done any solder bridges, mis solders.

EDIT:If the LED doesn't flash, it's time to break out the multimeter. Remember that the battery voltage is switched by the input jack, so you have to have a plug in J1 when you take measurements. First, make sure that pin 8 of the 555 has about 8.5 volts on it (presuming that your battery is actually 9 volts.) If you don't see this, review all of the power connections and test the continuity of the associated board traces. When you have the power straightened out, start testing the continuity of every joint and trace in this part of the circuit. Once the oscillator is working, try the effect again.

If there are problems with the sound, first check the supply voltages on the modulator side. You need to have +8.5 volts at pin 8 of the chip and +4.25 on pin 3 and pin 5. If the voltages are there, see if you can narrow the trouble to one stage by using the guitar amp as a signal tracer. Again, you may have to check each PC board trace and connection with an ohmmeter.

I would check pin 8 of the 555 first. Which is not getting correct voltage, and between the battery and pin 8 theres only one resistance. If it's not getting correct voltage maybe you've got somethign wrong with the wiring :S
From the web you posted.

[smallbearelec]

From the voltages, it looks like there are wiring errors. QSQCaito is right that you should see about half the supply voltage at pin 3 and pin 5 of the op-amp, for example. Try doing the troubleshooting as I suggest in the article: Start with blank copies of the schem and layout. Use you meter to verify that you have continuity between things that are supposed to be connected, and nothing shorted. Mark off the connections with a highlighter as you work. You will find your mistakes this way, and the pedal will work when you get All the mistakes out.

Regards
SD

[studiostud]

SD,

could you possible send me a photo of the wiring on one of the Tremulous Bears that you've done?  That would come as great help.  Let me know.  Thanks.

Jeff

[smallbearelec]

If you haven't already, please write me at smallbearelec@ix.netcom.com. I will do my best to get you going with the troubleshooting.

[BingsMcnasty]

Hello DIYers. I am new to the community and figured now is as good a time as any to get into the swing of things.

Sooooo... I have built this version of the Tremulous Bear and am having the same issue. Different Voltages in the IC's but I also have no sound (except for a crackling that seems to change with the adjustment of R25 ) Ive already gone through this with the continuity tester and everything checked out. Ive been going over the wiring again and again and am in need of some assistance at this point.
I wasn't sure about the orientation of the two toggle switches but I would think I would still get some sound even with those backwards.
and I am also getting some serious noise touching the dpdt switch at all.

Here are my voltages.

IC1

1 4.76
2 4.5
3 4.36
4 0
5 9
6 4.51
7 4.5
8 4.39

IC2

1 0
2 .9
3 9
4 9
5 .47
6 .39
7 .08
8 9

Q1

s .74
g .5
d .39

Q2

c .67
b .68
e .4

Q3

c .4
b 0
e 0

Thanks in advance for the help.

[studiostud]

you know it's funny... it's been 3 years and 30-40 pedals (including several tremulus lunes and an EA trem) since I gave up on that circuit and to this day, that I still the only circuit that I have yet to get working....

However, I don't want to leave you with just that....  here are some things to look at.  Your IC1 is pretty normal.  IC2 however is not.  I can't remember what IC2 is but if my memory serves me correctly, I think it's some sort of opamp.  If that is the case then on most opamps and dual opamps, pin 4 is connected to GND and thus should be 0V.  Since your IC2 Pin 4 is registered at the input voltage, that leads me to believe that there is either a solder bridge somewhere or something is connecting to GND where it shouldn't be.  My first advice would be to grab your multimeter and check all your GND connections and make sure they are at 0V and have continuity with the GND path.  Then check any connections that are near the ground path and make sure that they don't having any continuity with the GND path.  If that doesn't yield any positive results, then just check and recheck over your wiring for solder bridges and cold joints.  That's one thing I've learned over the years.  It's a Murphy's Law, really.... no matter how many times you look it over, only after the circuit breaks your spirit will you look it over once more just for kicks and find the hairline solder bridge...

Good luck, man.

Jeff