GGG PT80 no effect help!

[mmaatt25]

Hi,

I've just complete a GGG PT80 using one of their RTS boards. I haven't substituted any of the components, they are as the list of materials.

I get my bypass signal crystal clear (so we know I can wire a 3pdt switch!)  when I engage the effect the LED lights up, but my signal is exactly the same and the 3 pots have no effect on the signal at all?  Where's my delay!!!

Power is from a 9v 200ma Boss effects PSU putting out 8.93v

TL072 voltage

pin1  5.97
pin2  5.97
pin3  5.96
pin4  0
pin5  5.42
pin6  5.96
pin7  5.97
pin8  11.97

MAX1044 voltage

pin1  8.87
pin2  4.31
pin3  0.01
pin4  0.17
pin5  0.36
pin6  4.38
pin7  6.58
pin8  8.87

PT2399 voltage

pin1   5.06
pin2   2.53
pin3   0.01
pin4   0.01
pin5   2.89
pin6   2.52
pin7   0.54
pin8   0.56
pin9   2.53
pin10 2.53
pin11 2.53
pin12 2.53
pin13 2.53
pin14 2.53
pin15 2.53
pin16 2.53

NE571 voltages

pin1   0.01
pin2   1.82
pin3   1.82
pin4   0
pin5   0
pin6   0.91
pin7   0.91
pin8   1.83
pin9   reading kept decreasing
pin10 reading kept decreasing
pin11 reading kept decreasing
pin12 reading kept decreasing
pin13 11.97
pin14 1.82
pin15 1.82
pin16 0

78L05 voltages

5.06
0.1
14.79

78L12 voltages

11.95
0.1
14.79

2N5088 voltages

5.18
5.72
11.97

The only thing that i did do was power it up without the 2N5088, (i socketed all the IC's, 78L's  & 2N5088) i forgot to put it in, i don't think this would have damaged anything??

I had a probe around with my audio probe and only got hiss from pin of the PT2399, normal signal from pins 2, 3, 8, 11, 12, 13, 14 & 15 of the NE571 and normal signal from the TL072

Anyway I'm out of my depth now so could with a little help. I know there's a steep learning curve coming up, I'm just not sure where to start.

Many thanks

Matt

[KazooMan]

I have built three PT80's based on the GGG layout.  Two (mine) with boards I made and components I purchased and one from the kit that I bought for the son of some friends and helped him assemble the pedal. All three work fine.

I just opened up one of my working pedals and took some voltages.  I did this with a regulated 9.0V supply, with no input or output connected to the pedal.  All pots at half mast.  

Here's how my readings compare to yours.

TL072 - identical within tolerance

MAX 1044 - identical within tolerance

78L05 - identical within tolerance

78L12 - identical within tolerance  

PT2399 - all agree with yours except:  pins 7 and 8 are at 0.86 and 0.82

NE571 - pin 1 is at 1.06, pins 6 and 7 are at 6.52, and pin 16 is at 1.20

I am not knowledgeable enough to know just what these readings mean, but at least they should point you to the right parts of the circuit.

Note that both my PT2399 and NE571 have an embossed dot on one end AND a half-moon notch at the other end.  The notch is the indicator for the IC.  Make certain that your chips are in the correct way.  

Hope this helps.

[mmaatt25]

Thanks KazooMan, the pins on the PT2399 where my voltage is different both go to caps (104's) to ground, so is the voltage in the PT2399 the problem?

I've cleaned the whole board, there were a couple of potential bridges, not solder, is rosin?? anyway i cleaned them all up and now can't see any bridges.

Could the a bridge have damaged the PT2399?

I used my audio probe and get no signal from all the pins on the PT2399 except pin 5 where theres a hiss.  Also I'm not getting any signal on pins 2&3 of the NE571n, these are the input i think?

It looks like the problem is the PT2399 or around that area.

I've tried to trace the audio path from GGG's parts layout (basically a labelled PCB) here http://www.generalguitargadgets.com/pdf/ggg_pt80_lo1.pdf but can't find any signal to the PT2399!!

Any help appreciated.

Many thanks
Matt

[MmmPedals]

check the ne571 pins 1 and 16 for shorts to ground.
Now check again.

[mmaatt25]

Hi MmmPedals, checked the ne571 the only pin going to ground is pin4, checked pins 1 and 16 for ground, all ok.

Thanks again

Matt

[KazooMan]

It's a bit easier to follow the signal path on the schematic and compare it to the layout.  The input signal comes in and goes through a .047 uf cap and into pin 5 of the 072.  That pin is also connected to the 12 V supply through a 1 M resistor.  The signal comes out of this section of the 072 and heads to pin 11 of the 571.  It's here where your voltages start going bonkers, so I would look very carefully at all of the connections to components.  Also be certain that there are no shorts between adjacent pins on the 571 socket. 

The signal exits the 571 at pin 10 and goes to pins 15 and 16 of the 2399.  Do you have a signal at pin 10?  If so, check all of the components between there and the 2399. 

I really think (as does MmmPedals) that you problem is centered on the 571.  You can also check the pins of the socket for continuity to the pcb traces leading to them to make certain you don't have a bad solder joint.

Keep trying and keep us posted.  This is a great pedal once you get it working!

[mmaatt25]

Thanks for your help KazooMan,

Checked there's no signal at pin 10 of the Ne571?

Checked as suggested for NE571 socket for continuity to PCB, every pin is OK?

Does this mean that the NE571 is damaged?

Thanks again

Matt

[KazooMan]

Well, a fried IC is a possibility, but I would still do more troubleshooting on the board and components. 

Check extra carefully, one more time, for any solder bridges.  Good lighting and a magnifier helps.  Reheat all of the solder joints to eliminate the possibility of a cold joint.  Check the value of every component one more time versus the layout just to be sure.  Once you are certain that all of these issues are OK, then you may need to try another IC.  You want to be certain that everything is proper before trying another chip.  If there is an underlying problem that fried the first one, you may fry the second one as well.  Still, sometimes you just get a bad IC. 

The GGG PCBs are really first rate, so I wouldn't anticipate any problem there.  If you have etched your own board I would have some concerns.  I have etched what looked like perfect boards and then couldn't get the pedal to work no matter what I tried.  I then etched another board and moved the components over one at a time and had instant joy.

[mmaatt25]

Update!

As suggested reflowed the whole board, every joint.
Checked all my pinouts when i put them all back again.
Checked all component values.
Still no signal from NE571 pin10.

I've ordered another NE571, i think i must of damaged it. it's socketed, so i didn't cook it, i did find a couple of possible bridges may be they were the cause.

I'll update when I try a new NE571

Thanks

Matt

[mmaatt25]

Update!!

Put new NE571 in and still no signal (audio probe) from pin 10 or pins. Pin 10 is the feed to the PT2399.

I've got signal at pins 11 & 12 so I know signal is getting to NE571.

I'm lost, don't know what to check next.

Help

Matt

[KazooMan]

Matt:

Sorry to hear that the IC didn't solve the problem.

Can you get a decent digital camera (not a cell phone) and take several pictures of both sides of the board and your wiring?  That might help a second and third pair of eyes see something.  If you have no other way to post pics, you can upload them to tinypics.com for free and embed the link in your message. 

[mmaatt25]

Hi,

Here's the link for the photos

http://www3.truprint.co.uk/thumbnailshare/AlbumID=3772168011/a=3797017011_3797017011/otsc=SHR/otsi=SALBlink/COBRAND_NAME=truprint/

Matt

[KazooMan]

Matt:

I had a look at the photos.  Very nice build.  Now if it would only work!

At first glance I thought that the stomp switch was wired incorrectly.  The wiring is different that that shown in the documentation you can download from the GGG site.  However, from the way the switch is wired it looks like it will perform the identical function.  I have no idea why they would change this in teh kit instructions.

Is there a chance that the board could short out to the backs of the pots when the board is in place?  It looks very close.  I assume that you have tried the pedal with the board up in the air and not down hard on the mounting posts. 

Other than that I haven't seen anything yet.  Cap, transistor, IC, and diode polarity is correct.  I will have a harder look at the components and soldering.

[mmaatt25]

Hi KazooMan,

I have tried it out (although there is enough clearance) just in case of that very problem.

The issue as far as I understand is the lack of signal from pin 10, but I cant work out why? I've got signal going in via pin 11!

Many thanks

Matt

[KazooMan]

Matt:

It is hard to see some of the colors in the pictures well.  What are the bands on all of the 22K resistors?  

[mmaatt25]

22k are red red black red brown (metal film 1%)

[mmaatt25]

Update!!!

Rechecked all my IC voltages after replacing NE571. MAX1044, TL072 & PT2399 all as reported earlier, however the new NE571 now reads:

Pin1   0.5v was reading 0.01v this is still wrong should be 1v
Pin2   1.78v
Pin3   1.78v
Pin4   0.002v
Pin5   1.79v
Pin6   6.49v was reading 0.91v
Pin7   6.49v was reading 0.91v
Pin8   1.78v
Pin9   1.78v was unable to get steady reading
Pin10 1.32v was unable to get steady reading. This is still wrong should be 6v
Pin11 7.36v was unable to get steady reading. This is still wrong should be 1.8v
Pin12 3.97v was unable to get steady reading. This is still wrong should be 1.8v
Pin13 11.99v
Pin14 1.78v
Pin15 1.78v
Pin16 0.005v

So it appears the NE571 was part of the problem. I took the PT2399 and measured the voltages on the NE571no difference! I'm still waiting for another PT2399 to arrive.

Thanks

Matt

[thedefog]

Hey Matt,

Have you tried using an audio probe on the signal path yet? I always have a mini alligator clip handy and going to my output jack when debugging.

Check your polarized components again too and make sure the orientation is correct.

Also, In my experience, 98% of my problems just come from improper wiring, and not from faulty components or bridging. I've yet to come across a bad component in the 50+ projects I've built. Frying them, however, is a different story 

[mmaatt25]

Sorry to resurrect this, but it's still not working

I've had my audio probe out and I'm stuck.

My set up is RG's quick and dirty audio test oscillator feeding a signal to the input of the PT80 and my audio probes connect to my ruby amp, set up works well.
I'm using this layout from GGG http://www.generalguitargadgets.com/pdf/ggg_pt80_lo1.pdf
And this schematic for reference http://www.generalguitargadgets.com/diagrams/pt80schem.pdf

I get signal to Pin11 of the NE571.
I get signal at Pin12, through the 22k resisitor and 1uf cap to the repeats pot.
I'm not getting any signal after the 36k resistor which connects to pin12 NE571 and am not getting any signal from pin14&15 NE571?
I'm not getting any signal at pin10 NE571?

I've haven't probed any further as there seems little point as pin10 Ne571 seems to me to feed signal to the PT2399.

As stated above I have changed the NE571, which resulted in the voltage changes i listed. I can only assume i damaged the first one?

Any help appreciated as always


Many thanks

Matt

[robertreynisson]

Did you get the new PT2399? I've had several problems with my build. One was because I wired the pots incorrectly, and the other was because of a solder bridge. I also had a compander chip die on me. I tried everything after that. I got a now compander and I could get some delays happening but they were distorted... Tried changing all the caps and nothing... Still distorting. I ended up edging another board and repopulated it with the same parts except for the caps to get it working for me.

This is a relatively tight layout and every time I do some soldering on this I end up having problems with bridges. Go over EVERY tight spots with a multimeter and test for connectivity and compare it to your layout. I use press and peal and it's a great help to keep the blue paper with the layout after you edge it and compare it to the board, cause you can look through it from the front and behind. It's a bitch but it pays of when this sucker works! Good luck