Help Troubleshooting a Tonmann Paramix

[Freekmagnet]

Hi,

I assembled a Guitar PCB Paramix board and mounted it in the box.

Here's the schematic:
http://www.guitarpcb.com/PDF%20Files/ParaMix%20v4.pdf

Bypass works, the effect doesn't. The LED doesn't even light up.

I was pretty careful when I populated the board. I looked at each joint through a magnifying loop, they all seemed good. The wires going into the board are secure and none of the wires seem to be crossed. I tested the stomp switch and it seems to be OK.

I pulled out the IC, and the LED lit up.

What would be my best line of troubleshooting attack from here?

Audio probe? Multimeter to trace continuity from the battery?

Any suggestions appreciated. Thanks.

Jeremy

[bluebunny]

Check out the sticky DEBUGGING thread at the top of this forum.

[samhay]

Looks like the IC is shorting your V+ to ground. Did you have it the right way round and can you try another?
Take voltages with AND without the IC socketed.

[Freekmagnet]

I will take some voltages and post them later today. Thanks.

I think I do have another IC floating around somewhere. The IC on the board is socketed and I'm pretty sure it's pointing in the right direction. I already tried flipping it around last night and there was no change.

[Freekmagnet]

Here's a question - should I try another IC first or wait until I take voltages? Say there's something wrong my wiring, would I risk damaging the IC?

J

[Freekmagnet]

I'll have the voltages shortly.

[Freekmagnet]

Voltage from the wall wart into the board: 9v

IC 1 -

1: 4.4v
2: 4.2v
3: 4.1v
4: 9v
5: 4.1v
6: 4.4v
7: 4.4v
8: 4.4v
9: 3v
10: 1v
11: 0v
12: .75v
13: .75v
14: 8v

With the IC Removed:

1: 0v
2: 0v
3: 4.4v
4: 9v
5: 4.4v
6: 0v
7: 0v
8: .25v
9: .25v
10: .25v
11: 0v
12: .25v
13: 0v
14: 0v

[mth5044]

Am I missing where the build doc even says what IC1 is? Seems very sloppy, but I'm assuming you are using a TL074. Your power rails look good on pins 4 and 11. Check all the voltages where VB connects (on R13/14/2/6) and also triple check the values of R2 and 6.

[Freekmagnet]

Am I missing where the build doc even says what IC1 is? Seems very sloppy, but I'm assuming you are using a TL074. Your power rails look good on pins 4 and 11. Check all the voltages where VB connects (on R13/14/2/6) and also triple check the values of R2 and 6.

You raise a good point - I don't see anything about the IC in the documentation either. It is a TL074. I must have read it somewhere, 'cuz I'm not smart enough to make something like that up. I'll look again.

I'll take a look at those VB connects and resistor values.

[Freekmagnet]

Am I missing where the build doc even says what IC1 is? Seems very sloppy, but I'm assuming you are using a TL074. Your power rails look good on pins 4 and 11. Check all the voltages where VB connects (on R13/14/2/6) and also triple check the values of R2 and 6.

You raise a good point - I don't see anything about the IC in the documentation either. It is a TL074. I must have read it somewhere, 'cuz I'm not smart enough to make something like that up. I'll look again.

I'll take a look at those VB connects and resistor values.

Here it is - TL074

http://www.guitarpcb.com/apps/forums/topics/show/8230446-paramix-by-tomann

[samhay]

There is something wrong with your VB supply - it looks ok at pin 3, but is getting loaded down badly elsewhere. Check resistor values and the orientation of your electrolytic capacitors.
If that all checks out, take a look at the wiring to your switch too.

[Freekmagnet]

Am I missing where the build doc even says what IC1 is? Seems very sloppy, but I'm assuming you are using a TL074. Your power rails look good on pins 4 and 11. Check all the voltages where VB connects (on R13/14/2/6) and also triple check the values of R2 and 6.

Am I missing where the build doc even says what IC1 is? Seems very sloppy, but I'm assuming you are using a TL074. Your power rails look good on pins 4 and 11. Check all the voltages where VB connects (on R13/14/2/6) and also triple check the values of R2 and 6.

OK I checked those voltages. I took two measurements - one on each side of the resistor. The first number is the side going closest to the IC.

R13: 4.4v / 9v
R14: 4.4v / 0v
R2: .25v / 4.4v
R6: 4.4v / .25v

R2 and R6 appear to be the correct values at 1M.

[Freekmagnet]

There is something wrong with your VB supply - it looks ok at pin 3, but is getting loaded down badly elsewhere. Check resistor values and the orientation of your electrolytic capacitors.
If that all checks out, take a look at the wiring to your switch too.

I'll take a look at this next.

[jimilee]

One of the resistors was listed as a 100k, but was suppose to be a 10k. I had an issue with one also. Search the tech forum over there.

[mth5044]

You're getting the VB on the correct side of resistors, but a 4.15V drop across the 1M resistor seems... not right.

[Freekmagnet]

Well, I followed some advice I found from elsewhere. I reflowed all of the joints and even replaced a few wires. I swapped out the IC with another.

No change. The pedal is dead. Voltages on the IC are roughly the same (within an couple decimals).

I searched all over the Tonmann forum and couldn't fine any reference to a 100K vs 10K resistor.

Anyone else? Any suggestions?

Thanks,

Jeremy

[duck_arse]

any Ic, ALL IC's, only go one way, socket or solder. mark the IC you tried both ways, and put it somewhere you can't reach.

pins 8 and 9 are connected on the circuit, so they must show the same voltage at all times. with the IC removed, and power off, use your ohms/continuity range on dmm to check the resistance between each of pins 8, 9, 10 and ground. and pin 12, for both sw1 positions.