221/Repairs
Common Problems
Failing PSU
The 221 has a switching power supply. It has
a transformer coupled trigger circuit which produces
a DC level base trigger. It gets fried when the battery
gets old and draws too much current.
More often than not, the T633 Transformer (part number 120-0876-00)
is the thing to fail.
Failed capacitors
justanotherelectronicsblog@YouTube found C714 short when fixing his 221