After electrify, check the preamplifier integrated piece of U2 (KA2220) pin voltage, in addition to the first (7), (8) feet of 0 v, the rest of the pin voltage is within the normal range. Shut off the power supply first (7), (8) feet of no short circuit phenomenon, but the first foot (8), (9) between positive and negative resistance to close up. KA2220 (8), (9) foot inside has a resistance, the resistance to an internal load in the collector of a transistor. Try a 2.2 k Ω, 1/8 w resistor and received the first (8), (9) foot, connected to the power supply, the machine work record and playback are back to normal, troubleshooting.Pvfservice manual download site