21
Index Everest Servicemanual v 3.0
BOX 155 • S-954 23 GAMMELSTAD • SWEDEN • PHONE +46-(0)920 203080 • T46-(0)920 203085 • E-MAIL [email protected] • http://www.indexbraille.com
Logic to test faulty hammer or driving electronic
Hammer
The forming hammers, 6 positive and 7 negative, are of similar type as used for daisy wheel printers.
They have an expected life time of 200.000.000 strokes and the hammer tip is based hardened steel to ensure
maximum life time. Voltage 40 V, Current 4-6 Amps, Resistans cold solenoid 1,9-2,0 Ohm, maximum
temperature 130º Celcius, Plunger stroke 3.8 mm.
Driving electronics
The driving electronic of the Everest is of a very stable and ruff design. In most cases when electronic driving
problem occurs, it is a result of a hammer with chort circuit (0 Ohm) or bad handling of the main board/cables.
Handle the Main Electronic Board of the Everest with the respect that a six layers SMD CPU board with CMOS
components require. Always use antistatics packing components and make sure that you and your work place is
properly grounded.
The thirteen hammers and the stepper motor for the printing head are controlled by a pulse flow from a FIFO
memory. The stepper motor pulses drives direct the two stepper motor driving circuit RIFA 3770.
The puls flow used to drive hammers are created in the FIFO memory, passing a buffer step (74AC834) and
controls the seven driving circuits (U35-41) for constant current regulation to the hammers via the power
transistors T3-T15.
Test hammers and driving electronic
Make a test printout, POWER ON + ON LINE. (Picture A) Evaluate the test printout and check which hammer
that cause the problem. Make sure that the printer is set for 42 characters per line interpoint mode, standard on
set-up C after system reset. If not, it can happen that a fault will not be displayed on the test printout.
Evaluate if there is a hammer or a electronics fault.
If, for example, there is no print on block 6, (Picture B) test it in the following way;
a) Open the front glass, take out the printing head and switch the connector cables between hammer 5 and 6.
(Picture C) When you have the printing head separate check the resistance on each hammer.
Shall be 1,9-2.0 Ohm, measure it on the printing head board.
b) Insert the printing head again and make a new test printout, POWER ON + ON LINE. (Picture A)
If the missed block (no 6) stays on the same side of the paper. It indicates that there is a mechanical problem
on the hammer, no 6 in our example. If the missed block (no 6) moves to the other side of the paper, it is an
electronic problem on main board or cable.
Note that the printout looks strange after switching hammers, so make sure that you understand the changed
printout before starting to work with the printing head.
Hammer-test
Summary of Contents for EVEREST
Page 2: ......
Page 56: ...D dokument index servicemanual smanev PM65 990903 ...
