Ballast Junior

[azrael]

I have a Ballast Junior here where sometimes there is no chorus effect occurring.
Now, I think this is related to the "lockup" issue of the PT2399. When I power it with a bench power supply, i noticed that it is drawing an unusual amount of current. around 135-140. But when I probe with a multimeter Pin 2 to see what's happening, the current draw drops and the effect begins working again. And the voltage at Pin 2 looks normal after this (around 2.5V)

Currently toying with the "anti-lockup" circuit (Q2 and its neighbors) but nothing yet. I tried the older value of 47 ohms for R24 just to see, with no luck.

One difference is that I have TL072s in both positions, as I didn't have a TL022. Will be trying a TL062 for IC3 tomorrow.

Should I also try swapping PT2399s? Any other fix ideas?

[madbean]

Something is sinking a whole lot of current but I'm not sure if it's your particular PT2399 or the anti-latch circuit. Using the TL072 for the other is fine - shouldn't have any effect.

Try removing the two TL072 and check the current draw again on power up and see if you get the same result. Check for any pins on the PT2399 having continuity with ground that shouldn't (on pins 3 and 4 should).

One other idea: try powering it up with IC3 removed to see if you have the same issue. Maybe let us know if the LFO is causing an issue.

Pic of the top of the board, too, please. And, report any other voltages that are out of line with the build doc.

[azrael]

Something is sinking a whole lot of current but I'm not sure if it's your particular PT2399 or the anti-latch circuit. Using the TL072 for the other is fine - shouldn't have any effect.

Try removing the two TL072 and check the current draw again on power up and see if you get the same result. Check for any pins on the PT2399 having continuity with ground that shouldn't (on pins 3 and 4 should).

One other idea: try powering it up with IC3 removed to see if you have the same issue. Maybe let us know if the LFO is causing an issue.

Pic of the top of the board, too, please. And, report any other voltages that are out of line with the build doc.

to be clear, when I probe pin 2, the current draw drops back to 40-50mA, and I can get chorus tones out of it again. So that's why I think the current draw may be related to the lockup issue. Only pins 3 and 4 are connected ground, as we would expect.

This is something my coworker built, his first pedal, so I'm helping him debug it. I've attached a photo

[azrael]

An update, I put in another PT2399 and the high current draw state has been fixed. Current draw is 37 mA when it is working properly.
However there are still issues where the chorus effect does not happen. I'm going to revert R24 back to 100 ohms.

[madbean]

An update, I put in another PT2399 and the high current draw state has been fixed. Current draw is 37 mA when it is working properly.
However there are still issues where the chorus effect does not happen. I'm going to revert R24 back to 100 ohms.

Interesting. Alternatively you can increase R25 to 100k. This will increase the charge up time on the anti lock circuit. So, at power up pin6 will see the 2k2 to ground then as the transistor switch is powered it will reduce to the total resistance to its minimum.

[azrael]

Interesting. Alternatively you can increase R25 to 100k. This will increase the charge up time on the anti lock circuit. So, at power up pin6 will see the 2k2 to ground then as the transistor switch is powered it will reduce to the total resistance to its minimum.

Okay, will take note. After changing back to 100 ohms, I was unable to make the lockup state occur again after multiple power disconnect/reconnects with discharge time in between. But I will probably do this if it occurs again, that sounds like an easy fix to make that boot up time happy.

I think that one PT2399 was definitely unhappy in the circuit, but maybe the TL062 also helped? In any case, my coworker seems happy as his first pedal works now!