tblo163
New Member
I`ve bought a couple of these from ebay,180W+180W Stereo amplifier,for MP3 Playback.After 5 minutes of use,they both failed.The units have Volume,Bass &Trebble pots(47K).They use a TDA7057AQ Amp & a NJR4558D J-FET for the Pre-Amp.The units are not drawing any current(apart from 0.03amps for the rainbow LED)The Amp IC is getting 12v & all Grnd connections are o.k.The Pre-Amp is getting 12v@pin8,Grnd@pin4, 5.53v@pin1, 6.64@pin2, 7.46v@pin3, 5.34v@pin5, 6.56v@pin6, & 5.42v@pin7.The TDA7057 is getting 1volt@pins1&7=VCI&VC2-DC-VOL-CONTROL,so the amp should not be in mute mode,The voltage to Vol-inputs 1&2(pins#3&5,look suspect,reading 0.19 & 0.09 respectively.I`m sure they should be more like 1.2v.That`s as far as I`ve got,I`m looking to find out what controls the Input voltges & which component is likely to have failed.The circuit boards look pretty well built,but I should have known better than to buy cheap products from CHINA.Thanks for any suggestions Terry,
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