Eachine EV100: no audio problem — cause, fix, and technical background — UPDATE

Some days ago I published a post on how to fix the totally broken audio on the $99 Eachine EV100 FPV goggles. As it turned out the inbuilt receiver module, a Sinopine SP338RX, is missing “some” components that generate the audio output.

Some people are lucky as their modules are only missing the 6.5MHz filter. The “blue pill” standard filter is easy to mount but will require drilling some holes into the goggles case as it is so big that the top plate will no longer fit. I think I will try to get my hands on a tiny SMD version of this filter (TPSKA6M50B00-R3).

Others, including myself, are not that lucky: In addition to the missing filter, their receivers are also missing all the audio circuity (C1, C2, C3, R1, R2):

In my previous post I recommended getting a cheap RX5808 module in order to obtain the matching parts as I did not have a schematic or the application note with the correct part values.

Lucky for all EV100 owners I got the required RTC6715 datasheet and application note from Richwave! I did a small sketch of the circuit that is missing in my receiver module:

Looks like I was quite close with the values I measured. In order to fix the EV100 receiver module without sacrificing a RX5808 module you can now go shopping at your favorite SMD component supplier to buy the following spares:

I updated the original post accordingly. As the PCB has a solid ground plane and is also soldered to the EV100 a lot of energy is required to heat the solder pads. If you own a hot air gun I would strongly recommend using it. If you are brave enough you can do it with the PCB mounted into the goggles (which I did) but I would recommend to remove the PCB before soldering.

If you do not own a hot air gun you might help yourself by using a hair dryer to preheat the PCB before you do the soldering with a soldering iron. Professionals sometimes use a pre-heating oven below the PCB on multilayer boards that are hard to solder as well.

That’s all for now. Happy soldering! A list of previous and newer posts regarding the EV100 can be found in this list:

• Eachine EV100 component analysis: Display module supplier and technical data — UPDATE (12/3/2017)
• Eachine EV100: no audio problem — cause, fix, and technical background — UPDATE (10/24/2017)
• Eachine EV100: no audio problem — cause, fix, and technical background (10/20/2017)
• Eachine EV100 component analysis: Video receiver module identified — Sinopine SP338RX (10/12/2017)
• Eachine EV100: gray bar & distorted image problem — cause, fix, and technical background (10/11/2017)
• Eachine EV100 component analysis: Video decoder chipset identified — MST706 (9/27/2017)
• Eachine EV100 diversity: to be, or not to be, that is the question! (9/22/2017)
• Eachine EV100 component analysis: Display module supplier and technical data (9/20/2017)
• Eachine EV100 $99 FPV goggle — Disassembly, Components & PCB pictures (9/18/2017)