Help modifying a DigiTech powersupply

[jwhmca]

I'm working on the internal power supply for a digitech Genesis 3.

I wished I had the schematic to post , but I can't find it anywhere...

Here is the issue. The unit seems to reset randomly. It most definitely seems worse when running from a generator (like diesel, I tour abroad a lot)

I took it apart and found a 3.3 volt regulator (BA033T) that runs really hot (can't leave finger on it)... Now here is where I'm at. The 3.3reg spec sheet says it should be "bypassed" duh. It says a 22uf tant is ideal. Digi is using a 10uf aluminum elec... Tant for heat stability I'm guessing?

They also recommend a .33uf on the input to ground which digi did not install. The heat sink is a joke.

Here is the deal I need help with. Of course, if any power Brains can think right away the solution or already know of this... fine But, I need to do as much as possible before my next show cause I have no way to test it here.

Does adding the input bypass cap protect against what a deisle generator might put out etc...

 

[JohnRoberts]

If the VR is running really hot but putting out clean 3.3V perhaps look nearby for a problem. Perhaps something the VR is powering is drawing excessive current, or the un-reg feeding the 3.3VR is higher V than designed for (uncommon but worth looking at).

I had a tiny SMD 3.3 VR running too hot to touch in a prototype and it was because the dumb design engineer (me) didn't properly account for power dissipation.

JR

 

[jwhmca]

John,

Do you think that running it off from "generator power" could cause an issue in not having the input to the regulator bypassed?

 

[JohnRoberts]

no..  but it is probably worth metering the generator voltage for high line when lightly loaded. 

JR