GGG PT80 no effect help!

[KazooMan]

Hi again Matt:

It certainly appears that you are losing your signal to a short to ground.  I looked again at your pictures and I cannot see any obvious solder bridges, but them again pictures are not as good as looking at the real board. 

I can't recall if I mentioned it in any of the replies I have posted, but I have also run up against the wall as the last poster stated and had to etch a new board.  Moving the components over one at a time gave a working pedal.  Never did find the problem. 

One thought I had that I cannot check from the photos.  The GGG board has through plated holes.  These are great to work with.  I do see several places where quite a bit of solder has come through the holes to the component side of the board.  I'll post a picture highlighting some.  You will need to check for solder bridges on the component side of the board, especially under the IC sockets and large components.  You can check the sockets for bridges between adjacent pins with a continuity checker or DMM.  Just be aware that some of the adjacent pins are supposed to be connected.  I know that you checked all of the pins for shorts to ground, but it may be more subtle than that with a short to an adjacent pin.

[mmaatt25]

Hi,

Yeah I did get a new PT2399, but i'm reluctant to put in.  

I'm not not getting any signal to the PT2399.

This build is on a GGG RTS board, so I dont think thats the problem.

I've reflowed every joint and checked for bridges visually and with meter???

You can see my frustration!!!!!!!!!!


Many thanks

Matt

[mmaatt25]

Cheers KazooMan,

I'll have a look at those.

Thanks for sticking with me on this, believe me I'm as bored of this subject as I am frustrated.

You see posts for help sometimes which go on and on, I got alot more sympathy/empathy now!

Thanks

Matt

[mmaatt25]

Hi,

I've had my audio probe out and I'm still none the wiser!!

http://www3.truprint.co.uk/thumbnailshare/AlbumID=3944808011/a=3797017011_3797017011/otsc=SHR/otsi=SALBlink/COBRAND_NAME=truprint/

The link shows two photos, one of the schematic with my attempt to trace the signal path and the other the actual layout tracing the signal path.

Orange is where I have an audible signal with my probe and blue is no signal at all!

Sorry to keep boring everyone!!

Matt

[mmaatt25]

If the PT2399 was dead would this effect the output of the NE571??

Many thanks

Matt

[mmaatt25]

Update!!!!

Tried a new PT2399, still nothing?

Can anyone who has a working version have a look at diagram showing signal with my audio probe. This must be a simple problem, cap not working etc?

Anyone who has the time help will be very appreciated.

Many thanks

Matt

[mmaatt25]

Think I'm getting somewhere with this.

1. I'm not getting any signal at NE571N pins 10, 14&15 additionally no signal at PT2399 pins 15&16.

2. If bend pin 10 NE571N so no contact with socket still no signal at pin10.

3. If I short out NE571N pin 11 (input signal) and pin 10  signal at pin14&15 and signal at PT2399 15 but not 16? (and vice versa shorting 14,15&11 NE571N).

If I take PT2399 out of socket and test as 3. I get signal at PT2399 pins 15&16?

I've tested the above with two NE571N's and two PT2399, same results. So it looks like two bad NE571N's??
I'm going to get a couple more NE571N's from a different supplier and try them.

Matt

[mmaatt25]

Too close things off, I put another (purchased from different vendor) NE571 and it lives!!

So the build was good just bad parts.

I changed the 22k feedback resistor on the NE571 to 8K2 in series with 10K and 15nf cap at junction to two resistors to ground and didn't really notice much difference, it still self oscillates when the repeats pot is past 3/4 (of full on)? Sounds very good anywhere below this, so it's not really an issue.

Many thanks

Matt

[j_wyatt]

This thread has been of great interest to me because I'm having an identical problem with a PT-80 build.  The thing is, though, I have one I built over a year ago that I've used at every gig since I built it so I was able to swap the 2399 and the 571 to see if that was the issue and they worked perfectly in my working pedal but not in the new build.    That was the first thing I did five days ago and I've been confounded since.  I also have a strange problem with the 914 adjacent to the indicator FET that feeds voltage backwards...I replaced it but the problem persists.

Think I might start a thread about it too. Ugh! here we go again...

Glad to hear you got yours going.

[KazooMan]

Great news!  I am glad that you finally solved the mystery.  Enjoy your pedal.  The PT-80 is a great delay.

[mmaatt25]

Audio probe really is the most useful tool for debugging.
Looking back now it was clear the NE571 was the problem. Signal entered the NE571, but didn't come out. I got too hung up thinking that the probability of two bad NE571's (from different vendors) was so low that the problem must lie elsewhere when all the evidence, especially the audio probe was telling that was the problem.
Also noting down results of checks as you go is a must, otherwise you have no idea of whats what!

Hope this helps others.

Matt