It worked! and then it didn't.... (Unison Double Tracker/Pythagoras v3)

[Yroc006]

Was so proud of my first FV-1 solder job until I did something stupid. Had the board on my testing rig, and was taking the power and ground lines off. I usually unplug the rig before doing this, but I was excited and up way past my bed time. Wasn't thinking. So, i pulled the power and ground off and the power slipped out of my fingers and made contact with the board, which is also the same time I remembered I had not unplugged my rig first. Plugged it all back in and the wet side was absent.

Started taking voltages and noticed that the schematic calls for 3.3v coming from the pin 1 of the L78L33. I was getting a reading of .36v on pin 1voltage out and 9.09 incoming voltage on pin 3. (In my head) Cool, might may not have fried the FV-1 and wasted 30 some odd bucks. All of the rest of the Vrefs are reading 4.5, which seems normal, cool. So, I swap out the L78L33 (several times). {PSA those things get HOLY$&%T hot} Voltage remains between .35 and .5 on the 4 new ones I tried.

This next part is to be expected, I just felt that I should measure for the sake of due diligence.

Took readings at the power in pins of the FV-1
pin 6 - .35
pin 8 - .35
pin 13 - .34
pin 16 - .35

24LC32A EEPROM
pin 8 - .35

Mostly i'm try to figure out if there is something I can fix, or if this is headed for the bin of shame. Seems like something is going on with the L78L33 given the voltages i'm getting, but i'm not sure what it would be since the incoming voltage seems correct and i've tried several different L78L33s. Just a bummer to lose a board to such a boneheaded mistake.

 

[Yroc006]

Wanted to try one more time. Still unclear why i'm not getting 3.3v out of the L78L33 (I'm making an assumption that is what I should be getting). Removed/Replaced the socket and tried a 5th L78L33 just to see if that might be the issue. I don't know if a fried FV-1 would cause these readings or not, but i'm guessing since the voltage issue upstream of the IC, it's not necessarily a fried FV-1, but i'm stumped. Any thoughts or ideas would be appreciated. Thank you!

 

[slubtle]

Did you end up getting to the bottom of this, mate? I have a sneaky suspicion that I'm in a similar boat with my build.

 

[PJS]

If you try and pull too much current from a regulator it will lose regulation (and get hot). An easy was to pull too much current is a short. I am thinking that it is likely that the FV-1 or the eeprom is broken and drawing too much current. If the eeprom is socketed that is easy to remove and then check. Also, use a multimeter and visual inspection to check and make sure no pins are shorted where they are not supposed to be.

 

[Yroc006]

Did you end up getting to the bottom of this, mate? I have a sneaky suspicion that I'm in a similar boat with my build.

I ended up buying another board and starting over. On the plus side, The second board works as it should.