PT80 Charge Pump overheating

[distinctlyamerican]

Hi folks. Having some weird issues with my PT80 Delay from GGG. I built this guy at least a year ago, has been working great until recently. I get bypass signal, i turn the pedal on and still get unaffected slightly colored signal. No delay though. I pulled the pcb out to inspect and the 1044 max charge pump was on fire. Once I let it cool down, I plugged the pedal in again. Within the seconds the charge pump was smoking hot. I'm a little confused as to how this is happening after a year. Possible I need to replace it? If anyone has any insight it'd be greatly appreciated. Here's a schematic/project file link: http://www.generalguitargadgets.com/projects/20-modulationecho/125-pt-80-delay

[R.G.]

OK, I'll try to remember what I said last time, before we lost the last week of posts.

It is very likely that the charge pump is being overloaded. Pull out both the 12V and 5V regulators. Power the pedal and measure the voltage across the 10uF and 1N914 diode just after the charge pump and before the regulators. It it's about 16-17V, the charge pump is operating. Let it operate for a while and see if it gets hot.

If not, turn it off, put in the 12V regulator. Fire it up. Does the input to the 12V regulator have 16-17V on it? And if so, does it make 12V on the output?

If so, turn it off, put in the 5V regulator. This or the PT2399 is what I really think is wrong, but the other stuff had to be checked first. Turn the power on. Still have 16-17V on the input to the 12V and 5V regulator? If so, do you have 12V on the output of the 12V regulator and 5V on the output of the 5V regulator?

Successful electronic debugging nearly always starts with verifying whether the power supply is functioning right or not.

[distinctlyamerican]

Great, thanks so much. Yeah sorry, I didn't realize posts were erased weekly, i had to go out of town last minute and didn't get a chance to follow through with the last post before it was deleted. I'll do these tests and get right back to ya.

[mistahead]

Actually its every three or four days (as selected by an RG designed pseudo-randomiser).

Hop to the debug buddy - no time to lose!

[distinctlyamerican]

It's looking like i'm only getting about 9v after taking out the regulators. Still gets burnin hot too.

[distinctlyamerican]

Huh. Reinstalled the regulators. Getting the same situation (led powering up, bypass signal, noneffected signal) but the charge pump no longer overheats.

[Govmnt_Lacky]

Helpful suggestion...

Dump the MAX1044 and replace it with an TC1044. Voltage tolerance is MUCH better 

[distinctlyamerican]

Noted!

[armdnrdy]

Make sure that it's a "TC" and not a "LTC"

The LTC states that it guarantees 9 volt operation. The TC goes to 12 volts.

That's one more than eleven isn't it!

[R.G.]

It's looking like i'm only getting about 9v after taking out the regulators. Still gets burnin hot too.

That means the charge pump is dead. Time for a new one, as noted.

[rogerinIowa]

it is unlikely, due to the fact that the unit HAD been working well in the past, but I had an issue with a charge pump getting hot a couple of years ago. The 10uF electro caps I had used in all my other builds were rated too low for the voltage, I switched to 25v 10UF caps and bingo, it worked without excessive heat. My guess is this isnt the issue, so just file this under a friendly non-sequitir remembrance intruding on present day time