Odd PropBoard Behavior


Hi @Joecool,

I don’t know Li/FeS2 batteries. If I have to try one of these, I would choose the Li-ion ones.

I always try my best to help, and what’s recommended has been discussed already, but please understand I cannot guarantee for every battery manufacturer or do research for all kind of batteries. For your special case (AAA or AA Li-ion) I can give some advice or opinion, but I can’t tell you to blindly buy something I don’t know or I have not tested. On paper it might work, but what would happen if I tell you to buy those batteries, that at the end are not good enough because [insert unforeseen reason here]?


Oh, absolutely! I totally understand. Electrical engineering just isn’t quite my forte, so I’m just looking for a second set of eyes to make sure I haven’t missed anything obvious. For example, the current draw requirement you mentioned.

I’ll give a few things a try and see what happens. Thanks for the guidance!


Finally getting back to this project after a few months.

I’ve started using two 18650 batteries, 3.6V each. They’ve solved most of the odd behavior I was experiencing. (Hurray!!) There are two problems remaining:

  1. The sound is still quiet and “vibrates”, i.e. cuts in and out at a high rate per second
  2. The board is overheating when I keep the batteries connected.

RE #1: I’ve tried different speakers to no avail, and checked the volume in the program. (It’s set to 7.) No idea what the problem is there. Any suggestions would be helpful.

#2 is almost certainly related to that diode I had to re-solder, because it’s no longer on the board. :sob: (No way to find it either. I’ve moved this project a couple of times in the last couple months, so the part could have fallen anywhere.) Any idea which diode that one is on the schematics? (If I know that, I can refer to the hardware list and possibly find an equivalent replacement.)


Hi @Joecool,

The diode is a BAT60JFILM.

Regarding sound problems:

  1. Are you still using the lightsaber demo, or PBSaber, or a program you wrote?
  2. Can you try with another SD. Perhaps this is too slow to read from.
  3. Has it ever worked? Or it did worked but after the hardware issues it started to sound bad?

About the temperature problem, it’s hard to say what could be. You can check if when you soldered the diode or when it broke, the pads were left joined somehow.


Thanks, Ivan!

  1. I’m using the older lightsaber demo code.
  2. (and 3.) It used to work just fine with the same SD card.

I don’t see any solder where the diode was; I think the pads lifted off with it. (Been looking into PCB pad repair online.)

Here’s a link to a few photos of the board, if that helps. (Apologies for the quality. I don’t own a macro lens. Could get some really close up shots through my work though, if needed.)


Hi @Joecool,

The board is in a pretty bad condition. It may be a shortcircuit somewhere, but at this point I cannot precisely tell what’s going on

Regarding the diode, if the pads were lifted off, I cannot see how you could re-solder it.


Hey Ivan,

There are ways to repair a lifted/removed pad, but it takes specific equipment. Pretty sure my work has this equipment somewhere, so there is some hope.

Yea, I’m not happy with the condition of the board, either. It’s entirely my fault, of course. Soldering over and over again with old solder heads did this. I’ve bought new solder heads to prevent additional damage, and in the future, I’ll solder wire connectors to the board so I don’t end up toasting the thing like I did on this project. Live and learn, I guess. (This was a really good learning experience for me, so that’s something.)


Update: After finding the time to speak with a PCB specialist at my office, I’ve done some work overhauling this thing. The reason the board was so toasted is that I was using a silver solder, which has a high melting temperature. I’m now using a lead solder (in a fume hood) which has a much lower melting point.

I’ve also bought and secured a new diode to replace the one was that ripped off the board. (The PCB specialist helped me make a new connecting terminal! :slight_smile:)

As for the problems I was having, I disconnected the LEDs to make sure they weren’t causing any problems, and secured screw terminals to the board to prevent further heat damage. I’ve also replaced the speaker and wires connecting to it.

Here’s a video showing the audio problem I’m having. I’m using the audio files recommended in the tutorial (the ones here). As I mentioned previously, the sound “vibrates” and is quiet. The current speaker is Digikey p/n 433-1147-ND, though I’ve tried a few others as well that I bought for this project.

Things I’ve tried:
-Replacing the speaker and wires (currently 24 AWG multi-strand wires)
-Replacing the audio files
-Changing the audio volume in the program
-Disconnecting the LEDs (to prevent excess power drain from the two 18650 3.6V batteries)
-Resoldering speaker / wire connections
-Resoldering the screw terminals to the speaker
-Resoldering the screw terminals to the batteries

Any ideas what might be happening?


Hi @Joecool,

Thank you for posting the video.
A PropBoard sounding like that is something we haven’t seen before. Probably a damaged codec or amplifier, o some of the passive components around them. It’s really difficult to diagnose it. If you feel like, you can replace the amp first and then the codec, but they are such tiny components (specially the amp) that’s probably quite difficult to do it without the right tools.


Thanks, Ivan! I looked at the amp under a microscope at my office, and it looks fine–no visible damage to any of the pins coming off of it, or to the ‘box’ itself. Here’s a picture of it. (I’m not sure where the white scratches to the upper left came from, but they’re only surface-level. I examined it from multiple angles.)

Is the “codec” the component identified in the schematics as “U3” and “WM8523GEDT”? If so, I don’t have a pic of it yet (I can get one if it’ll help!), though it looks fine to the naked eye, at least.

Could the problems be inside the black casing of the components, hidden from view? (If that’s the case, I can definitely give it a try to buy replacement parts.)



Yes, and this is mostly what could be happening, or some passive component around them (like capacitors, etc.).

Would be difficult to diagnose without an oscilloscope and some knowledge on general electronics. I can’t assure you that changing components will bring back the board.