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8.
PRINTER TIMER
The printer timer which is located on the underside of the top cover is responsible for setting up the timing
to the printhead. This is dependent upon the paper speed and the millivolts per division.
This adjustment needs to be done
if
the printhead adjustment did not help the light printing or
if
there are
dashes in the ECG.
8.1
Board Replacement
Remove the top cover and lay
it so
you are looking at the underside. Remove the two screws holding
down the Printer Timer Board. Refer
to
Figure 3 for locations. Disconnect ST1 0 from the printhead and
remove the board. Replace and secure
it
back down with the two screws.
8.2
Adjustment
1.
Locate the Printer Timer Board (see Figure 3) and solder wire to R4 (see Figure 5).
2. Disconnect STlO from the thermal printhead.
3. Connect a 30kOhm resistor between pins 3a and 4b on ST1 0 as shown in Figure 5.
4. Insert a wire into pin 2b of ST10 and another wire into 6b, 7b or 8b for GND connection. Refer to
Figure 5 for location.
5.
Put top cover back on unit and connect all cables, but the cable to the LCD. Refer to Figure
1,
This will
allow you to raise the cover to make your adjustments.
6. Connect your ground lead to the wire connected to either pin 6b, 7b or 8b and the positive to the wire
connected to R4.
CAUTION:
Ensure that the wire going to pin 2b is not shorting to anything
7.
Turn V2 fully counterclockwise. See Figure 5 for location. Turn the unit on (the LCD will not come on
-
it
is disconnected).
8. Press key
1
(25mWs) and key 4
(+lo) to
put the unit into 2.5mWs. Then press key M to put the unit
into Manual mode.
9. Press the START key and set charge time for C4 to 0.62ms by adjusting VR1. See Figure 6, diagram
1.
1O.Press the STOP key and connect the probe to the wire in pin 2b of ST1 0.
11
.Press the START key and adjust VR2 for the correct pulse width per Table
2
below. Refer to Figure
3
for the location of the resistance label on the printhead. Refer to Figure 6, diagram 2 for example.
When adjustment is set, turn the unit off and remove the cover. Disconnect all wires that were installed
and connect ST1 0 back to the printhead.
Put the top cover back on, connecting all cables and ensure that the unit is operating correctly.
8-1
2
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