A customer has brought in an EH Digital Delay pedal, looks like late 1970’s. No Output. Signal is good to and from digital section. signal stops in analog output section at a chip whose markings have been removed. A schematic would help. Or any suggestions as to what the unmraked chip may be – I don’t think it is the compander as I have identified another unmarked chip as the NE57x. To be precise, this is the EH Digital Dealy with Magna Storage and Echo Chorus