Editing Macintosh SE/30 Troubleshooting (section)

== Single Vertical Line — Horizontal Sweep Collapse ==

A picture that has collapsed to a '''single vertical line''' is a failure of the '''horizontal''' sweep. This is common on both the [[Macintosh SE]] and the SE/30, which share an analogue board.<ref name="ssse30" />

'''Switch the machine off the moment you see it.''' A concentrated line will burn the phosphor permanently within minutes.

The culprits, in the order worth checking:

# '''Cracked joints at the yoke connector (P1 / J1).''' Thermal cycling over decades fatigues these joints, and this is by a wide margin the most common analogue-board fault on a compact Mac. Reflow all four pins with fresh solder while the connector halves are still mated, or the heat will distort the plastic and you will not get them back together.<ref name="cmrn" /> Pina also notes the plug itself is often burned by this stage and may need replacing.<ref name="dms" />
# '''C15.''' The non-polarised high-frequency capacitor in the horizontal circuit, 3.9&nbsp;µF 35&nbsp;V bipolar low-ESR.<ref name="c5147" /> Pina specifies it as 3.9&nbsp;µF NP 25/35&nbsp;V HF and recommends replacing it with a '''3.9&nbsp;µF NP 100&nbsp;V HF''' part. Its failure shows first as poor horizontal linearity — items on the left wider than items on the right — then as a bright vertical line, then as smoke.<ref name="dms" />
# '''R19.''' 220&nbsp;Ω, ½&nbsp;W, 5&nbsp;%. When it burns out the machine chimes normally but shows a relatively dim vertical line. Pina adds that linearity coil '''L3''' should be vacuum-desoldered and resoldered with fresh solder at the same time, or the fault returns.<ref name="dms" />

A '''single horizontal line''' is the opposite fault — a collapse of the '''vertical''' sweep, a different circuit. Apple adopted the TDA1170 vertical deflection IC on the compact Macs after the Plus, and that is where to look.<ref name="cmrn" />