This machine is a M17 machine, a small signal processing circuit for TA8880. Observation that often appear in a horizontal line, shaking the antenna when HERSHEY'S bad.E88service manual download site
In accordance with general repair experience, should be a IC output.E88service manual download site
This machine is of a few small circuit board inserted in the two block of the circuit board, connected by the connector and cable. Field output circuit in the X board, with a small adjacent small intervals, to remove maintenance, field output IC452 (LA7833), X3 and its peripheral devices have the socket weld. In order to insurance, the author carefully cleaning, repair welding again.E88service manual download site
Replace the X board is energized, the fault is still. It seems that only by experience not, I took the self-made "Stethoscope" -- with earplugs do signal tracing device (see chart 1) "to" the signal correlation point. The X board is inserted in the socket D9 D board, D9 V.TRIG (field in the foot end trigger), normal when you can hear the sound of the frame rate, but this can not hear the sound, the fault point before. Search circuit (Fig. 2 field trigger pulse and the feet to the A3 the feet for cable. Listen to D3 and feet along the circuit fault state of the silent, A3 foot fault state sound, shows the breakdown between these two points. Look carefully, see there is a small crack around the A3 of the foot, repair welding after troubleshooting.E88service manual download site
Maintenance of D9, D3, found in the socket of A3 solder joint is poor, and the one one welding. In order to insurance, and in the R401 back end (A point below) between D9 and the feet and a cross line.E88service manual download site
Summary: the maintenance of earplug gradually compression fault coverage, quickly find the fault point. Hindsight, maintenance or take a small detour, the original rocking antenna HERSHEY'S bad, in fact, have suggested that the fault point is located on the A tuner, still according to formulary thinking from the field output circuit of maintenance.E88service manual download site