ADM 3a with no horizontal scan

[dwight]

Try renewing the thermal compound.
Also, look for any really hot components on the 5V
lines. Tantalums don't always smoke.
A lot of older circuits also used a shunt resistor across
the regulator to share part of the load. These were usually
the square wire wound resisters. These often fail because
of internal corrosion. When open the regulators carry the
full load.
Dwight