Small Stone debug

[deadspeaker]

Finished Tonepad's Small Stone last week. I checked orientations, traced through the schematic with a highlighter, and checked the voltages. I'm probably missing something obvious. IC5 seems kind of off. I swapped it with another and got the same results. Please help me interpret these voltages.

Battery was 8.22 volts at the start of it all.
IC1
1= 0
2= 0.8
3= 0.6
4= 0
5= 0.6
6= 0.07
7= 5.5
8= 0

IC2
1= 0
2= .8
3= .6
4= 0
5= .6
6= .06
7= 5.5
8= 0

IC3
1= 0
2= .8
3= .6
4= 0
5= .6
6= .06
7= 5.5
8= 0

IC4
1= 0
2= .7
3= .6
4= 0
5= .5
6= .1
7= 5.5
8=0

IC5
1= 0
2= 1.2
3= 1.5
4= 0
5= 0
6= 0
7= 5.5
8= 0

Transistors:

Q1
E= 4.6
B= .01
C= 1.6

Q2
E= 3
B= 4.4
C= 5.2

Q3
E= 2.7
B= .03
C= 2.6

Q4
E= 5.5
B= 2.5
C= 2.4

Q5
E= 2.1
B= .09
C= 2.6

Q6
E= 5.5
B= 2.7
C= 2.5

Q7
E= 2.7
B= .02
C= 2.6

Q8
E= 5.5
B= 2.6
C= 2.4

Q9
E= 5.5
B= 0.2
C= 2.6

Q10
E= 5.5
B= 2.6
C= 2.4

Q11
E= .5
B= 1.2
C= 1.2

Q12
E= 1.3
B= 1.1
C= 1.6

Q13
E= 2.3
B= 0
C= 0

Q14
E= 1.4
B= 1.9
C= .6

[Kerly]

No sound at all? or something specific
If its no sound you might want to check your offboard wiring

[deadspeaker]

it bypasses fine. The effect is sort of a far away cop car siren. When the pot is turned all the away one direction there is sort of a super fast pacman noise.  No guitar gets through or at least it is too quite to hear.

[oskar]

http://www.tonepad.com/getFile.asp?id=7

IC5 seems kind of off. I swapped it with another and got the same results. Please help me interpret these voltages.

Battery was 8.22 volts at the start of it all.

IC5
1= 0
2= 1.2
3= 1.5
4= 0
5= 0
6= 0
7= 5.5
8= 0

IC5, Pin 5 should be ~0.7v
I'ld start checking the R21,R22, R23.
If you have a voltage at their junction then lift IC5 and go hunting underneath...

[deadspeaker]

The junction of R21, R22, and R23 measures at about .3 volts. For a second pin 5 of IC5 had .3 volts before I realized that the pot was turned all the way open.

If you have a voltage at their junction then lift IC5 and go hunting underneath...

Should there not be a voltage here? Pin 5 on the data sheet is referred to as "amplifier bias input." I guess being an input, it should not put out any voltage, but receive voltage from the bias. Am I on the right track?

[Sody54]

Not to derail this, but would these readings be the same on an original EH stone?  Would give me a new starting place for debugging mine.  Haven't had any luck so far

[oskar]

Ok. Incidentally I've got a russian small stone disassembled and I just pulled it out and lended a battery from the
fire alarm     :-)
This machine has the original 3094 ic's. What voltages do you want?

Vbat unloaded 8.84
Vbat in circuit 8.81

IC 1-4 ( filter )
pin
1     4.2 - 4.6
2     3.51
3     3.49
4     0
5     0.60 - 0.65 ( changing while sweaping )
6     ~3.5
7     8.6
8     8.6 ( pin 7 and 8 connected )

IC 5 ( LFO )
1     1.7 -1.9
2     4.5 - 7.0
3     4.5 - 7.0
4     0     
6     0.54 - 0.65
6     0.6 - 0.7
7     4.5 - 7.0
8     8.6

divider feeding rate potentiometer 1.8V

[deadspeaker]

Well I went over it again and still can't find anything wrong. Are you sure pin 5 of IC 5 should be more than zero on the tonepad version?

[oskar]

Are you sure pin 5 of IC 5 should be more than zero on the tonepad version?

Yes. This don't differ between the 3080 and the 3094.
If you have 0V you either have an open connection inside the chip ( it's deader than dead ) or you're feeding it nothing.
In you're case chip 1-4 are reading allright and chip 5 is not. The rate pot has two wires going to it. One should read the same as pin 5 and the other ~1.5-2v... Also something is sucking on the powerline. 5.5 is a bit low.

[deadspeaker]

Well like I said, the one lug on the pot is getting .3 volts, while the other two that are connect to pin 5 are at zero. Also I rotated chips, so IC5 is not dead. So you think that maybe some thing that is not suppose to be connected to power is?

[oskar]

The difference between the voltage over the battery poles in and out of the circuit is because the battery has an intrnal resistance and the heavier the load the more the voltage will sink. Basic voltage division. ( When the battery is dying the internal resistance increases and thus the voltage output will go down ).
On the Small Stone there is a 470R resistor In series with Ri (the battery's internal resistance).
If the 9 volt battery is drawn down to 5.5V which is ~60%...
Then from the 470R resistor to ground you have a load somewhere around 1k...
Now there is the mysterious 0.3 volts on the divider... the divider is fed 5.5V Right? So either of the resistors are wrong or
you measured with the pot completely open and pin 5 is shorted to ground ( or both and little trolls have moved into the capacitors )
Remove the battery and meassure the resistors around the divider. Also remove IC5 and measure resistance to ground from all pins.

Good night....     
skar

[deadspeaker]

I've only done part of what you said. I lifted the resistors to make sure they are who they say they are. They are. I won't be able to work on it again until probably Friday, but when I get the chance, I'll do the tests you suggested, and re-debug with a fresh battery. Thanks for all the help.

P.S. The pot I'm using is a B1M. I read that real Small Stones require reverse audio pots. Will this affect mine's ability to operate? 

[oskar]

I've only done part of what you said. I lifted the resistors to make sure they are who they say they are. They are.

Ok. Probably a dead end. I think if you'ld measure the divider once more ,making sure the pot was on full resistance, you would
get a higher reading.

P.S. The pot I'm using is a B1M. I read that real Small Stones require reverse audio pots. Will this affect mine's ability to operate? 

When you turn the pot from ccw to full on, you will notice that it will respond less in the beginning ( or the end, depending on how it's wired ).
That's why the pot is made to skip the boring parts... If you find this to be an issue for you ( later on, make it work first...       ) there are way's to hook up a linear pot for a nonlinear response..

[deadspeaker]

Sharped the soldering iron tip and reworked some joints. I had all the chips and transistors out at the time. I put them back in and used a fresh battery. I works now! Thanks for the help

Now I need to fix the volume issue and maybe convert the linear pot to audio.