How to fix a Numark TTXUSB spinning backwards?
I want to repair this turntable without buying a new motor PCB or control PCB. In the beginnin it spins normally and then suddenly spins backwards or not at all. After spinning the turntable manually or letting the turntable get warm, it works normally. Thus my guesses are broken diodes (for spinning backwards) and capacitors (because it works after it got warm or stayed on for some time). Internet research said to exchange the motor pcb. I could not locate any diodes on the motor and exchanging the three big capacitors did not resolve the problem. Does anyone have experience with this device? I already asked for a datasheet here Does anyone have the service manual for the Numark TTXUSB? , but it seems that it is an older version of the device, because the numberings of the parts don’t comply with the PCB.
In DJ forums people say to exchange the Toshiba TA7259P IC http://pdf.datasheetcatalog.com/datashee... , which breaks often due to overheating. The PCB in this device, doesn not have this chip, but six complementary 2SB1340 ⁄ 2SD1889 transistors attached to a big heat sink, which apparently do the same job as the Toshiba IC. I could also try to exchange these transistors, but I have no explanation how a broken transistor could result in the platter spinning backwards. I assume that they are used as an amplifying circuit. Please correct my if I am wrong!