Datasheet for the 79MXX series of medium-current negative fixed voltage regulators, a 162 KB PDF. The last digits of the part number give the output, for example -5 V, -12 V or -15 V, and the series is rated around 500 mA. The document lists pinout, input range and recommended capacitors. Take care during repair: the pin order of negative 79-series regulators differs from positive 78-series parts, so ground and input are not where you may expect them, and misplacement on a board will damage the replacement.
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