PROBLEM DESCRIPTION: When the DWP is turned on, the printwheel spins
at high speeds or the carriage jams to the right or left side of the
printer.
CAUSE:
1. The drive circuits in the printwheel servo or the carriage servo have blown.
2. If it's an old logic PCB, one of the buses may have broken connection with
the PCB.
There are 4 revs of DWP Main Logic PCBs (A1,A2, B, and C). The older
rev PCBs (A1, A2, and B), have very fragile busses which are light
colored strips mounted lengthwise along the component side of the PCB.
If the PCB is flexed lengthwise (even slightly), pins on this bus will
break from contact with the PCB. Most often this break is invisible
to casual inspection.
One of the most common problems a break on the bus can cause is to
prevent a power supply voltage from getting to the encoder PCB.
This will cause the encoder PCB to output an error voltage to the
servo loop. If it's the printwheel servo loop the printwheel will
spin in one direction. If it's the carriage servo, the carriage
will slam to one side.
Since it is so easy to break these buses, many well intentioned
techs have accidently damaged PCBs before installing them causing
the same symptoms to occur after replacement as were there before.
CURE: "Carefully" replace the logic PCB.
If the above cure doesn't fix the problem, refer to the Tech
Procedures to obtain the general troubleshooting for this product.