Cave Dweller only noise repeats

[Liustucru]

Hello,
I've been lucky since now because I always managed to debug my non working board alone.
A friend came on tuesday to build its Cave Dweller.

I ordered all components as usual from Banzai and Mouser except for the PT2399 IC which is from eBay (http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=160635992207&ssPageName=ADME:L:OC:FR:3160)

We triple checked all components.
It was very tricky to make the Panasonic 1µF cap fit.
I ordered 1/4W resistors so they are all standing.
The board will be boxed up in a 1590B so I needn't bother saving space.

He soldered all components and we tested the board with my test rig.
Here's the problem:
- totally clean signal with echo and dwell pots all the way down
- whatever the position of time pot, we only hear noise repeats when turning either echo or dwell pots

We tried several PT2399 (all coming from the same eBay supplier)
We socketed C3 to try different values

No change !!!

I took some photos of the board:









I included an audio probe to my test rig but never used it yet. Honnestly I don't know where to probe.

Any help will be very welcome.

THANK YOU

[jkokura]

When you say noise repeats, do you mean that it's not repeating your guitar signal, or that it's noiser than you expected it to be?

This delay's repeats are a little noisy by nature...

Maybe some audio clips would help us out some.

Jacob

[Liustucru]

I know the delay's repeats can be noisy but there is only noise.
I cannot record some audio clips right now but I will try later.

Can it come from bad PT2399s ?
I ordered 10 pieces from eBay and all of them give the same result.
I also tested different 78L05 regulators.

Any idea ?

[Liustucru]

Has anybody already experienced only noise (not noisy) repeats with bad PT2399s ?

[gtr2]

It's most likely not your PT2399's.  If you have another circuit handy that uses the PT2399 you could always double check.

I'd reflow all your solder joints.  A couple of them look suspect of being cold joints.  Take out the pt2399 and transistor first 

Also what is you voltage on pin 1?

Josh

[midwayfair]

Has anybody already experienced only noise (not noisy) repeats with bad PT2399s ?

IME, this came from some pins not making proper contact. This is a problem with larger sockets I've found.

[Liustucru]

Hello,
I made a video with my phone.
I hope it will help to debug this Cave Dweller: http://youtu.be/iHJoCcVhnP0

I reflowed or re-soldered all solder joints (without the ICs of course).
I also measured the voltages on the PT2399 pins:
1: 5.03          16: 2.48
2: 2.50          15: 2.51         
3: 0              14: 2.51
4: 0              13: 2.51
5: 1.17          12: 2.51
6: 2.48          11: 2.51
7: 2.74          10: 1.42
8: 3.07          9: 2.51

It's most likely not your PT2399's.  If you have another circuit handy that uses the PT2399 you could always double check.

This is my first delay 

Thank you for your help !!!!!!!!!!!!

[alanp]

I was having a similar problem with my Dub edition CD.

Problem turned out to be a section of the groundplane being cut off from ground due to a break in a track. Coax a solder bridge over it, and bobs yer uncle.

[Liustucru]

I was having a similar problem with my Dub edition CD.

Problem turned out to be a section of the groundplane being cut off from ground due to a break in a track. Coax a solder bridge over it, and bobs yer uncle.

Thank you for the info.
But it may be harder to trace with a fabbed board  

[Liustucru]

Any idea where the problem may come from ?

Thank you.

Hello,
I made a video with my phone.
I hope it will help to debug this Cave Dweller: http://youtu.be/iHJoCcVhnP0

I reflowed or re-soldered all solder joints (without the ICs of course).
I also measured the voltages on the PT2399 pins:
1: 5.03          16: 2.48
2: 2.50          15: 2.51         
3: 0              14: 2.51
4: 0              13: 2.51
5: 1.17          12: 2.51
6: 2.48          11: 2.51
7: 2.74          10: 1.42
8: 3.07          9: 2.51

It's most likely not your PT2399's.  If you have another circuit handy that uses the PT2399 you could always double check.

This is my first delay 

Thank you for your help !!!!!!!!!!!!

[gtr2]

7 and 8 look too high and 10 should be around 2.5V

[Liustucru]

7 and 8 look too high and 10 should be around 2.5V

Can you tell me which components to check or replace ?
I've checked all resistors with my DMM before soldering but I may have made a mistake.
I've also checked all caps' labels and I never had any issue with panasonic caps.

THANK YOU

[gtr2]

Well..I wasn't thinking... 7 and 8's voltage would be dependent on the delay time pot setting...

Use your audio probe and check pins 12, 14, 15 tell me what you find at each pin.  Set the dwell and echo at min settings.

Josh

[Liustucru]

Well..I wasn't thinking... 7 and 8's voltage would be dependent on the delay time pot setting...

Use your audio probe and check pins 12, 14, 15 tell me what you find at each pin.  Set the dwell and echo at min settings.

Josh

Hello Josh !
here is the new voltage reading with the dwell and echo pots at min settings :
1: 5.02                 16: 2.50
2: 2.50                 15: 2.50         
3: 0                     14: 2.50
4: 0                     13: 2.51
5: 2.37                 12: 2.51
6: 2.50                 11: 2.50
7: 2.85-3.35          10: 1.35-1.50
8: 3.30-3.40          9: 2.50

where there are 2 values, it means its oscillates between the 2 values.

With the audio probe, here's what I hear (same pot settings):
pin 14 & 15 : clean signal with some background noise
pin 12 : noise with some background clean signal

THANK YOU FOR YOUR HELP !!!

[gtr2]

Pin 12 should have the delayed signal.  14 and 15 seem ok

Check the continuity between ground and Pin 3 and also ground and pin 4.

It's almost like the PT2399's are locking up