Bad wiring

[kevbot]

Hi I'm having trouble navigating this forum so please forgive me if this is the wrong area for newb questions.

I've started a project (tonepad.com) EH style pulsar. I tested it last night with a good 9v battery and found it not working. When turned on I get a low signal, off it goes back up in volume and the battery got very hot. I then pulled the battery and got the same results. There is one thing I should also mention.The offboard wiring I used two switch craft mono jacks because it's all I had on hand. I found a GGG wiring diagram for true bypass DPDT and changed the negative lead of the battery clip from the input ring to the input sleeve since the rest of the ground goes there and mono jacks have no ring. Please understand this is my first electronics project and I honestly don't understand most of it (which means I probably botched the whole thing up!)

Please feel free to ask any ??s and assume I'm an idiot with electronics.

[artifus]

the battery getting hot would indicate a direct short between + and -. do you have a continuity tester or audio probe?

[.Mike]

Yikes. That's quite complex for your first project.

If your battery is getting hot, something is pulling too much current. In short, you most likely have a short.

I personally would recommend an easy project as your first build-- something with a much better chance of success, like a single transistor booster.

Otherwise, find and fix the short. If it doesn't work after that, head over to the Debugging Topic and follow the procedure.

Mike

[kevbot]

the battery getting hot would indicate a direct short between + and -. do you have a continuity tester or audio probe?

No I haven't built these yet. I'm sure I will soon!

Yikes. That's quite complex for your first project.

If your battery is getting hot, something is pulling too much current. In short, you most likely have a short.

I personally would recommend an easy project as your first build-- something with a much better chance of success, like a single transistor booster.

Otherwise, find and fix the short. If it doesn't work after that, head over to the Debugging Topic and follow the procedure.

Mike

Ok, I'll look for a short. Yeah this project was a bit complicated for a first timer... I'll look into that procedure as well.

Thanks for the help!

[kevbot]

Looks like I had the ground and 9v+ to board mixed up. No the battery stays cool. The circuit is still not doing what it should do. I've started gathering voltages but won't be able to finish until later. So far the polarized caps are mounted correctly but I'm finding that the voltage at S2 is 0 no matter what I do. I still get low volume when turned on, battery or not. I'll check into it more tonight!

[kevbot]

OOOOOOOOOOkay, so here's my procedural debugging result. I hope this makes sense!
EH Pulsar by Tonepad.com

Diagram: http://www.tonepad.com/project.asp?id=14
Offboard wiring: http://www.generalguitargadgets.com/pdf/ggg_sw_dpdt_tb_gi.pdf

I used a 2x2 perfboard with .1" holes, point to point wiring (very sloppy..) I followed the wiring very closely, just ran the wires (and jumpers) around like spaghetti. The jumper from Q2 to ground is moved on the board but not changed in the circuit. As for the offboard wiring I followed very close but I used two mono switch craft jacks so there's no "ring" connection on the input. Instead I used the sleeve (the same as the ground.)

The only parts I subbed were the transistors. All 3 2N5088 were subbed with NTE123AP. I don't understand what the pinout means but I assumed it meant which lead is the E,B,C, so I just matched the schematic. Most resistors are 1/4 watt 2%, a few are 1/2 watt 2%.

The power is a standard negative center 2.1 barrel and 9v battery clip

The pedal is a Tremolo clone but when used produces only a quiet guitar signal. The change happens whether or not the battery is hooked up!

• Effect on, powered: quiet guitar.
• Effect off, powered : normal guitar.
• Effect on, no power: quiet guitar.
• Effect off, no power: normal guitar.

!! Also R15 (Rate) increases and decreases volume. !!

Here are the results from the voltmeter on the circuit: First I tested the caps to double check I didn't put one in reverse. There are 4 polarized (electrolytic) caps, here are the values with the 9v at 8.53v:
C2: +8.52 -0;
C3: +4.48 -0;
C4: +4.48 -4.48; (is that right?)
C5: +4.42 -0

Later I tested the transistors and OP Amp, 9v at 8.21: (subbed from 2N5088 to NTE123AP)
Q1: 0,0,0
Q2: 0,0,0
Q3: 0,0,0
At this point I double checked I had these in correctly but acording to the data sheet they were fine...

The single OP Amp was functioning:
1: 4.32
2: 4.32
3: 4.10
4: 0
5: 0 (both 4 and 5 are wired to ground)
6: 7.62
7: 7.62 (6 and 7 jumped, tested on ic, not solder)
8: 8.21

Notes: I did some poking around with the voltmeter and noticed the onboard switch S2 had no signal neither did R12 or R13 which come from Q1's emitter.

Here come the pics! Sorry about the quality. I can't find my camera so I used the webcam.

[Pyr0]

If all 3 transistors have 0v on each pin something is not wired right. Start checking the voltages at both ends of each of these resistors - R17, R18, R19, R20, the end with the little triangle from the schematic should all be 9v.

[kevbot]

I've tested the 4 resistors. Here's what I got:
Battery: 8.41
R18: 8.4
R17: 7.56
R19: 7.72
R20: 8.31
I noticed that R18 was slowly gaining voltage and had stopped at 8.4 so I tested the battery again and got 8.31v - just like R20. It seems a part of the circuit is draining voltage. Make any sense?

[kevbot]

I've retested the wiring and see that all four resistors are reading 9v on the positive side (there'd be something very wrong if they didn't right?) but two resistors (R 17 &19) are a bit low on the negative side towards the transistors. Does that make sense to anyone? I don't understand electronics well but since these four are the first components in the circuit and wired parallel shouldn't the be the same voltage on both sides? Sorry I'm so green about all this!

[PRR]

> two resistors (R 17 &19) are a bit low on the negative side towards the transistors.

What means "a bit low"?? 8.9V? 7V? 0.6V?

[kevbot]

Sorry, I really meant to post those! I've disassembled the board and recreated it. I etched a PC copper board because my point to point wiring was pretty crappy looking. I'll have info tomorrow on that. As for the original circuit for anyone interested: with the battery at 8.35 R17 was 7.59v R19 was 7.74v on the negative side.

[kevbot]

I have rebuilt the circuit and got the same results! This time it is on a homemade PCB. All copper tracks are conductive. I plug everything in (correctly) and with the pedal off I get a strong signal-with it off I get a lower but very much audible signal. I've found that R10 (depth) is acting like a volume pot! R15 seems to have no effect. Every lead is getting power including the transistors. I double checked the polarized caps.

At this point I'm guessing I'm overlooking something. Not sure what measurements to take to help here but this is what I've got: (9v battery now @ 8.25)
R17 & R 19 has the same dip in voltage as before around .70 & .5v respectively.
R10 (now acting as volume) has 8.15v on first two leads, second changes when turned clockwise from 7.5 to 8.15v
R15 constant 8.21v on all leads regardless
Input @Tip 4.13 (half of battery) @Sleeve 8.25v
Output @Tip 7.86 @Sleeve 8.25
I'm using a DPDT switch, top left and right are jumped, middle goto input and output and read 8.25v and 0 if off, bottom goto board in and out.
Also I have two ground pads at the top corners of the circuit and wasn't sure what to do so I jumped them as well. Is that right?

Is there something else I should test or does any of this look wrong? Thanks for looking.

[Pyr0]

It sounds like it's the wiring to/from the board that might be your problem. There is no way you should be getting those voltages on the tip and sleeve.
There shouldn't be any DC voltage on the input and output.
Where are you putting the ground connection of your DMM for the measurements ?
With a new board it might be worth posting new pics, both sides of the board and offboard wiring.

[kevbot]

With my DMM I'm using the ground probe to test each part (ie black probe on the tip, or on the sleeve, or on a lead) and positive probe on the DC jack positive lead.

[kevbot]

I've resoldered the input jack with a switchcraft stereo jack hoping to eliminate the problem. No dice. I also watched some youtube vids on how to use a multimeter since the question came up. Apparently I'm using mine backward. I tested after the new input jack was added. The pots are still acting the same where R10 acts as volume and R15 does nothing. Here are the results:
Battery @ 8.37v
Q1:
C 8.13
B 5.75
E 8.05

Q2;
C 8.12
B 8.32
E 7.96

Q3:
C 8.13
B 6.27
E 8.13-8.11 (it was changing back and forth alot)

U1:
1 7.55
2 7.79
3 7.89
4 8.15
5 8.15
6 7.75
7 7.75
8 8.34

R10: full clockwise
1,2,3: 8.10
counter clockwise
1,2: 8.04
3: 7.89

R15: full CW
1,2,3: 8.15
CCW
1,2,3: 8.10

S2
1 0
2 6.68
3 6.69
Sound doesn't change when switched so I didn't test it after switching.

As for the first 4 reasistors in question I retested them with COM probe grounded got similar results
NEGATIVE SIDE
R18 8.32
R17 8.31
R19 6.26
R20 815
POSITIVE SIDE
All 8.35

I can take a pic if it really helps. Is there anything in particular that I should focus on? I followed the diagram exactly and used the recommended http://www.tonepad.com/project.asp?id=35 'offboard wiring #2' method from the website. The schematicd doesn't show what to do with two ground pads but I just jumped the two as mentioned earlier.

[PRR]

Nothing seems to be at ZERO volts.

You expect some things at +9V, some things at Zero, and many things in-between.

In particular, Q2 Q3 Emitters are shown grounded, which should put them at dead-nuts Zero.

Find the missing connection that's not letting -9V (zero) into the circuits.