GGG PT-80 Troubleshooting

[trocker767]

Hi there, the PT-80 is the second DIY guitar pedal i have made. (The BSIAB2 being my first )

Anyways, i plugged all the chips in and the transistors into the sockets i made for them and nothing happened.
No sound or anything, even when i turned all the pots.
I can click the switch and the bypass works fine.

Every thing's stock, except i used a 17v charge pump so i can use a 9v power supply and I built it WITH the millennium parts included.
I used an NTE199 instead of a 2N5088, but i made sure I made the pin-out correct.
I used an NTE451 instead of a 2N5485 in the millennium circuit.
I used an NTE977 instead of a 78L05 +5v regulator.

The voltage going in and out of the charge pump are fine. (9 coming in and 16 coming out)

I measured all the voltages as follows:

+5 V Regulator Output: 5.1 V
+12 V Regulator Output: 12.2 V

2N5088(NTE199)
Emitter: 5.4 V
Base: 5.3 V
Collector: 12.2 V

PT2399
Pin 1: 5.1 V
Pin 2: 2.5 V
Pin 3: 0 V
Pin 4: 0 V
Pin 5: 0.7 V
Pin 6: 2.4 V
Pin 7: 0.7 V
Pin 8: 0.8 V

Pin 9 to Pin 16: 2.5 V

NE570
Pin 1: 0.9 V
Pin 2: 3.5 V
Pin 3: 3.5 V
Pin 4: 0 V
Pin 5: 3.2 V
Pin 6: 11.4 V
Pin 7: 11.4 V
Pin 8: 3.9 V
Pin 9: 11.3 V
Pin 10: 11.3 V
Pin 11: 3.2 V
Pin 12: 3.2 V
Pin 13: 12.2 V
Pin 14: 2.4 V
Pin 15: 2.4 V
Pin 16: 1.7 V

TL072CP
Pin 1: 6.1 V
Pin 2: 6.1 V
Pin 3: 6.1 V
Pin 4: 0 V
Pin 5: 3.1 V
Pin 6: 6.1 V
Pin 7: 6.1 V
Pin 8: 12.2 V


I've checked some other threads about the PT-80, but decided to post my own voltages etc. and the problem, from what ive researched here, is in the NE570 and TL072CP. But i realyl have no clue which is why im ehre to begin with

[bdevlin]

If you don't get steered in the right direction here by someone I'd be willing to cross check my voltage readings on my working unit against yours.

[trocker767]

aight, thanks man

[stankyfish]

Hi there, the PT-80 is the second DIY guitar pedal i have made. (The BSIAB2 being my first )

Anyways, i plugged all the chips in and the transistors into the sockets i made for them and nothing happened.
No sound or anything, even when i turned all the pots.
I can click the switch and the bypass works fine.

....

I've checked some other threads about the PT-80, but decided to post my own voltages etc. and the problem, from what ive researched here, is in the NE570 and TL072CP. But i realyl have no clue which is why im ehre to begin with

Did you try probing it?  I had the same symptom with my PT-80, only mine worked until I put it in the case and as soon as I did, it stopped working.  Turned out to be a component shorting when I screwed the cover on.  Probe helped me figure it out.

[trocker767]

Probing, like audio probing? If you could point me in the direction of a schematic that i could prefboard up or sumthin that would be great

[zjokka]

Audio probing is just taking the output and connecting it to the input with a big cap to protect your speaker.
Otherwise touch output wire to input. Does that give you any sound?


zj

I must have my PT-80 voltages around somewhere I hope..

[oldschoolanalog]

Probing, like audio probing? If you could point me in the direction of a schematic that i could prefboard up or sumthin that would be great

Go to GEO, click on "tech tips". It's in there.

[phil]

Probing, like audio probing? If you could point me in the direction of a schematic that i could prefboard up or sumthin that would be great

Try these urls:

http://www.geofex.com/FX_images/audioprb.gif

http://www.diystompboxes.com/pedals/debug.html

I find the Audio Probe extremely useful - Besides debugging it also gives you an idea of what happens at each stage ...

Hook up a sound source to the input of your circuit and start probing from there. When the sound stops, you've found the general area of the problem. Also, if you aren't getting the gain you are expecting or if the effect doesn't sound right, you may want to double check the circuit in this area as well.

[trocker767]

Well i made an audio probe and went through and got to the NE570 and realized that one of the end pins was bent and didn't go into the socket.

So I fixed that and went through the rest with the probe and now it works

But when i put it all in the box it shorts out sometimes so i gotta find that and i'm all good

Thanks everyone for ur help

[phil]

So I fixed that and went through the rest with the probe and now it works

Congratulations on getting your second pedal working! You gotta feel good about that!   

[trocker767]

Yeah, sure does

But i etched and made all my boards in my electronics class in highschool and the class is over now so i gotta find another way to make my PCB's

And I'm not too sure what i want to undertake next.....What exactly does a compressor do?

[stankyfish]

And I'm not too sure what i want to undertake next.....What exactly does a compressor do?

It decreases the dynamic range of your guitar signal.  It takes the input signal and decreases the ouput level of the signal when it crosses a given threshold.  2:1 compression at -3dB, for example, says that when your guitar signal exceeds -3dB, the compressor will give you 1dB of output for every 2dB that went in.

The effect is that levels are kept more consistent and it gives the guitar "punch".  It's kind of hard to describe -- you have to hear it.  Think the rhythm guitar in "Under the Bridge" by the Chili Peppers.

If you're going to build one, I'd suggest starting with an Orange Squeezer clone -- simple and very nice sounding compressor.