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Fosi BT20A pro - Lower voltage on 1 channel

Jun 30, 2023
Houston, TX
I have a Fosi BT20A pro that is measuring significantly lower voltage on one channel. With a 1kHz test tone, I’m seeing about 10v less on one channel. With a 60Hz tone, I’m seeing 24.2v on one channel and 1.3v on the other channel. I’m still fairly new to this, but given its worse with lower frequencies. Is this a capacitor issue? If so, which capacitors should I be focusing on? I see several near the potentiometers and larger ones near the outputs.

To be fair to Fosi, the amp has done well for how I use and abuse it. I use it in a mobile build and it drives the hell out of 2 x Deaf Bonce Arnold 6.5 and 2 x Pioneer 4” TS-B400PRO all mounted in an ammo can on the rear rack of my e-bike for several hours. I removed the amp board from the case and installed a proper heat sink and fan. I am basically using it as a board amp at this point. The amp has never shut down due to thermal overload. The unit runs off of a 48v lithium pack I built to fit the space. The pack is capable of 30amps continuous. I use it on a weekly party bike ride here in Houston and it is the loudest and cleanest mobile speaker on the ride. It drowns out other larger builds with multiple speakers mounted on trailers being pulled behind a bike.
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