"Little Angel" - Super Simple PT2399 Mini Chorus

[EBK]

Have we touched upon the possibility of counterfeit PT2399 chips yet?

[jfrabat]

2 sources both counterfit?

Sent from my EVA-L19 using Tapatalk

[anotherjim]

Well, underspec/faulty/fake goods get out by the backdoor and sold as legitimate somewhere - to some distributors as well as in small quantities via e-bay, alibaba et al.  I would not expect devices from "knowledgeable" dealers like SmallBear and the bigger traders (Mouser et al) to be suspicious as they likely either chose to, or have to buy from official sources.

If you assume they are first quality goods and should be ok, then you have to ask why aren't they now?

Static damage is the first suspect.

Are you still discharging the chips before use?

Low humidity where you are? This greatly increases the generation of static charge. I seldom have to worry about this -  we've only had 3 low humidity days so far this winter and there's none in the forecast ahead.

Insulated flooring/clothing/work surface? Same effect.

Leaky soldering iron (the tip is not grounded)? Can damage circuits if the chips are in the sockets while soldering.

Incorrect packaging? IC's should either be in an anti-static plastic tube, pressed into anti-static foam or a piece of polystyrene WITH a metal foil surface. If anything came packaged differently - loose in an ordinary bag (anti-static bags ok -  but the pins get bent) or on a plain piece of polystyrene then the supplier is very naughty indeed.

[jfrabat]

Incorrect packaging? IC's should either be in an anti-static plastic tube, pressed into anti-static foam or a piece of polystyrene WITH a metal foil surface. If anything came packaged differently - loose in an ordinary bag (anti-static bags ok -  but the pins get bent) or on a plain piece of polystyrene then the supplier is very naughty indeed.

The local dealer just gives you the IC.  No packaging.  The ones from amazon came in polysterene, no metal...  So I guess I need to order new ones?

[anotherjim]

In that case, I would definitely suspect those you have and order from another source.

[duck_arse]

I've just seen something in another thread, made me think - jfrabat - are you using the same pots as from your first angel build? I don't think we've ever seen them in any photos, is there a chance we might see them, with their wires and solders?

and while I'm grasping at straws, can you put your meter across the pot connection ON THE BOARD (power off, as we are measuring ohms) and turn the pot shaft - does the resistance actually change? what range of reading do you get?

[jfrabat]

I've just seen something in another thread, made me think - jfrabat - are you using the same pots as from your first angel build? I don't think we've ever seen them in any photos, is there a chance we might see them, with their wires and solders?

and while I'm grasping at straws, can you put your meter across the pot connection ON THE BOARD (power off, as we are measuring ohms) and turn the pot shaft - does the resistance actually change? what range of reading do you get?

Yes, they are the same pots.  I will take some pictures and readings tonight.

[jfrabat]

500k pot goes from 0.6 ohms to 482K ohms

100k pot goes from 7.0 ohms to 89.8k ohms

I think I got both on backwars, though, as 0 is at full clockwise turn.  Changing them is simplybreplacing pin 1 for pin 3, right?

[duck_arse]

IF those pot resistance measures are at the board, then the pot wires and the pots are ok. and yes, swap 1 for 3 if they work backwards [but log (A /audio taper) pots will feel odd, bunched one end when reversed].

and now your pots - those rivet/eyelets holding the solder tag against the carbon track/pot wafer are not for our use! don't be poking wires and solder thru them, cause if they expand or loosen or wiggle, the pot is shot. (or that connection is shot, anyway.) and poor solder connections that close to the pot body cause many a crying builder. so wrap the wire around the lug/pin and solder, or cut a very small piece of vero or perf, solder that to the pins, and then wires into the board.

[EBK]

To add to what Stephen said: In the future, do not solder pots that way, but don't unsolder these now or you run the risk of destroying them.

[jfrabat]

I took the readings at the pots themselves; I will retake the readings tonight (or tomorrow night, as I have a business dinner tonight) at the board to be sure.  As for the rivet, I think I now understand why I damaged so many pedals on my last build...  I just thought they were poor quality!  Live and learn, I guess... 

[jfrabat]

New PT's on the way (Smallbear).  It should take some time for them to get here, though, considering the season and the i ternational shipping.

[jfrabat]

Well, guys, I am officially stomped!  New PT's arrived, but no change in behavior from the pedal!  AAAARRRHHHGGG!!!

[EBK]

I understand your frustration.  Could you post some updated pics, including all the off-board wiring?  On the (somewhat) bright side, the fact that new PTs didn't change anything does narrow our focus a bit.

[jfrabat]

I'll trouble shoot it (AGAIN!) tonight, and take some new pictures.  I plan to:

1. Verify that all resistors and capacitors values are what they should be
2. That all IC's are connected the right way (yeah, I have done that before!)
3. Will most likely replace the pots (I got some new better ones from Small Bear and Mammoth to replace the cheap ones I have been using; but this I am leaving for last, as the ones I got were working last time I checked)

Anything else I should look for?

[jfrabat]

OK, this is what I have so far:

I bought this pcb from jmkpcbs.com

Here's the build instructions:



And this is how mine is looking as of today:





And the pots:



Changes from the plan are basically replacing the TL072 for a TL082.

Voltages are:

PT2399:
Pin 1      5.03V
Pin 2      2.51V
Pin 3      0V
Pin 4      0V
Pin 5      2.93V
Pin 6      2.42V
Pin 7      0.683V
Pin 8      0.696V
Pin 9 through 16    2.51V (Some movement when you first connected)

TL082
Pin 1      4.55V
Pin 2      4.55V
Pin 3      4.41V
Pin 4      0V
Pin 5      2.86 to 2.94V
Pin 6      3.00 to 3.04V
Pin 7      2.75 to 3.30V
Pin 8      9.04V

78L05
Vin      9.03V
Gnd     0V
Vout    5.03V

2N3904
C          2.42V
B          0.447V
E          0V

I will use the photo above to go through the resistance values to make sure I did not use the wrong ones.  I will also check the caps, but later on, as I have to do some stuff now...  For everyone's reference, this is also stated in the instructions:

L is the + connection of the LED
I is PCB Input
G is the ground for the switch (mine is soldered to the jack)
O is the PCB Output
+ is 9V in
- is ground for DC jack
GND is extra ground for 1/4" jack

[EBK]

Could you post a pic of the jacks (I/O and DC) and stomp switch?

[stallik]

phone's too small to look it up but will the replacement of the TL072 with at the TL082 make any odds?

[EBK]

phone's too small to look it up but will the replacement of the TL072 with at the TL082 make any odds?

It's compatible, but has better noise performance than the TL072, if I recall correctly.  Shouldn't cause any problems here.

[jfrabat]

Could you post a pic of the jacks (I/O and DC) and stomp switch?

Sure, I will post them tonight.  But I am pretty sure the problem is not there, because I get the bypass signal just fine and when I activate the effect, the dry signal goes through (if I lift the resistor, the dry signal goes away).  I will post them anyway, though, just in case.

phone's too small to look it up but will the replacement of the TL072 with at the TL082 make any odds?

It's compatible, but has better noise performance than the TL072, if I recall correctly.  Shouldn't cause any problems here.

I think I have some Tl072 in the OpAmp kit I bought; I could change them and see what happens...