Help MK-312BT no Power

[VirusHD]

Hello everyone,

I recently bought a Mk-312BT.
When I tested it for the first time, I noticed that the performance of the device doesn't even come close to the 2B & my DIY device. Unfortunately, I don't know what this could be at the moment and I'm hoping I might get a helpful answer here.

If I don't set the MK-312 to at least 80% in medium power mode, nothing is noticeable. What could be the reason? With the 2B I can't even get above 40% in the LOW.

Did I buy some junk?! I have already opened the device and it looks neatly soldered and wired. Visually I can't see any problem.

I am grateful for every tip.

Best regards

[edger477]

Normally 312 won't pass self-test at start if the voltage and mosfets aren't correct (it is rather sensitive).

Have you tried different modes? Do leds indicate operation when used? Have you tried adjusting MA knob?

[VirusHD]

The self-test returns ok F005.

Yes, I also tried different modes and the result is the same.

Yes, I also tried the MA button but it only does very little. The LEDs also flash corresponding to the pulses. I can also hear the device working (the up and down pulse)

This is what the device looks like after switching on. Adjust radio lights up constantly, is this normal?

[edger477]

Yes, radio light is normal, unit probably has bluetooth module, that is why it is on.

You tested both outputs? (L/R)? What electrodes? I recommend just sticky pads to ensure that it works normally and get a feel of the sensation. Try leaving MA somewhere at middle and try increasing the volumes. I built several of these and there was never unit that started up fine and did not work, only thing that could be there is that solder for the 3.5mm jack is not good, but very improbable that both l and r channels are affected.
Also if you hear the unit, that is probably transformers, they produce sound, so that means unit is working fine, and only thing between transformers and cable are those 3.5mm jacks.