Eggtimer Quasar not working - Short somewhere

[PhxRocketeer]

I got my Rx put together and it booted fine. Just finished putting together my Quasar and it isn't booting. Running it off of a power supply (6.5V, 0.5A limit) and it's got a short. Voltage drops to 2.25V at 0.5A. I did a thorough inspection and I can't see anything obvious. Probed most capacitors/resistors to make sure they weren't the culprits and all read high resistance. Can some better eyes take a look at these pictures and see if they can find an error? I thought I did quite a careful job so I'm confused.
-Shawn

 

[Voyager1]

I would start by checking for a short between the +V power input and GND (the -V power input) with a multimeter. If there is a short there, then you might need to remove the 3-pin rectifier. Check between the output of the 3.3V regulator and GND. Proceed around the board to check for shorts from power and signal tracks to GND. Recheck all your solder joints with a magnifier. You might have a solder bridge under one of the components.

 

[Tractionengines]

Did you put the cut off index card (or something else) as a spacer under the WiFi module. You can't have that module tight against main board.

 

[Voyager1]

Did you put the cut off index card (or something else) as a spacer under the WiFi module. You can't have that module tight against main board.

Good point!

 

[jgarbus]

Did you put the cut off index card (or something else) as a spacer under the WiFi module. You can't have that module tight against main board.

There is nothing noted in any of the manuals about adding an insulator at this location.

I'm mobile so it's difficult to confirm orientation. Have you tried a battery vs the current limited power supply?

 

[g.pitts]

Disclaimer that I've never built a Quasar, but I took a quick look at Cris' build instructions and there is one thing of note. In his build instructions, the PCA9536 shows the NXP logo rotated 180 degrees from what's I'm seeing with in your build. Can you verify that pin 1 on the PCA9536 matches pin 1 on the silkscreen of the PCB?

 

[PhxRocketeer]

Thanks for suggestions.
1) I have a healthy gap under the wifi module.
2) Power +/- Have 1900ohm, but I'm looking for ~40-50Ohm to explain the 500mA/2.5V
3) LDO Output to GND is 440Ohm
4) Yes, I tried a 9V alkaline. I know it's not intended for real use, but it ought to be able to boot up the buzzer. I don't want to put my power supply any higher and burn something up. Wish I had a thermal camera to see where the power is burning. If I can't find it, I'll do that next week with a friend

I'll do some more probing and find a magnifier. My biggest fear is that it's some little strand or trimmed part that snuck under somewhere. Any other ideas are welcomed.

 

[cerving]

It might be the PCA9536 I/O chip... do you have a clearer picture of the writing? I can't tell from these...

 

[PhxRocketeer]

g.Pitts I think you found it!

 

[PhxRocketeer]

Locate the spot for the PCA9536, it’s next to the .1 uF capacitor that you just mounted. Remove the PCA9536 from its package, it’s marked “PCA9536”; make sure you have the right one, there are others that look very similar! Pin 1 on the PCA9536 isn’t marked, so you’ll need to make sure that the writing is upside-up, on the side of the PC board with the Pin 1 marking square; it’s going to be the same as the 24C512 EEPROM that you mounted earlier.

These were the instructions. I may have misunderstood what they meant. To me this meant put the upside-up with pin 1 them same DIRECTION as the nearby pin 1. But you're right the picture is reversed.

Sweet. Thanks all!

 

[PhxRocketeer]

"You'll need to make sure the writing is upside-up in the same orientation as the EEPROM next to it and upside down versus the silkscreen."

This is what you mean I guess. I thought it meant 'same pin 1 orientation as EEPROM'

 

[VAXman]

Disclaimer that I've never built a Quasar, but I took a quick look at Cris' build instructions and there is one thing of note. In his build instructions, the PCA9536 shows the NXP logo rotated 180 degrees from what's I'm seeing with in your build. Can you verify that pin 1 on the PCA9536 matches pin 1 on the silkscreen of the PCB?


View attachment 665308View attachment 665310

Good catch!

He'll need a solder sucker and some desoldering wick to get that off. I'd wager that the best way would be to get small cutter and cut the leads away, and then use tweezers to remove the leads from the board's pads with a little soldering iron heat. Get a replacement I/O expander chip and resolder to the board. Cris *may* provide you with one or you can order one. The PCA9536 is available via Amazon and several other electronics parts suppliers (Mouser, DigiKey).

 

[PhxRocketeer]

Thanks for the help all! We got it flipped around and it’s functional now. I’ll find a way to test the I/O and confirm the part wasn’t damaged. Appreciate the help.

 

[g.pitts]

Thanks for the help all! We got it flipped around and it’s functional now. I’ll find a way to test the I/O and confirm the part wasn’t damaged. Appreciate the help.

Great to hear! Congrats on getting it working.

 

[PhxRocketeer]

Welp....this beautiful piece of machinery lasted a whopping 2 flights :-( On the second one it went up on a G80, flew beautifully to 3041ft (last GPS reading I got), but failed to eject (separate post on that). The rocket was built strong, but not "nose dive from 3,000ft" strong. RIP Eggtimer. Time to re-do.

 

[g.pitts]

Welp....this beautiful piece of machinery lasted a whopping 2 flights :-( On the second one it went up on a G80, flew beautifully to 3041ft (last GPS reading I got), but failed to eject (separate post on that). The rocket was built strong, but not "nose dive from 3,000ft" strong. RIP Eggtimer. Time to re-do.

Did you fly it with the original part that was rotated 180 degrees? If so, it is possible that the component failed (a "walking wounded" phenomenon).

 

[PhxRocketeer]

Oh, this was a motor ejection. The Quasar played no role in the failure.