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12. ADDITIONAL INFORMATION
Service position of the decoder panel
Decoder panels that are NOT provided with service PCBs may
NOT be placed in the horizontal service position (as given on page
5-3). These PCBs make closure in horizontal service position.
Stabilizer panel on the decoder panel
A stabilizer panel is mounted on the decoder panel for ERCO ICs
that function to provide a supply voltage of 6V.
The ICs that operate on 6V are labeled "6V" or "6V and 12V".
The stabilizer panel is given on page 8-3-1.
The bias resistor must be set so that the voltage between points 10
and 20 of the ERCO IC is +6 V ± 20 mV.
µP in the servo circuit
On servo panels with stamping A03 and higher, the bridge wire 67-
70 (in coordinate box F04 of the PCB drawing) has been replaced
by a resistor of 1kΩ.
This resistor is added to protect the µP against static charge.
DEMOD IC
On decoder boards stamped A02 and above, resistor 3515 has
been changed from 1Ω (1E) to 1kΩ.
This resistor has been modified to protect the DEMOD IC against
static charge.
Connector A12 on PRE-AMP + LASER PCB
During production, focus coils were temporarily used with the
winding direction reversed.
In this case, connector A12 on the PRE-AMP + LASER PCB is
rotated 180° in relation to the PCB drawing. The focus coils
supplied for service all have the same winding direction.
If a lens unit or PRE-AMP + LASER PCB has to be replaced,
attention must be paid to the position of connector A12.
When the connector is rotated 180° compared to the drawing in the
manual, the following measures must be taken.
• If the lens unit is replaced, assemble
connector A12 as given in the PCB drawing.
• If the PR E-AMPL + LASER PCB is replaced, rotate connector
A12 180° on the service-supplied PCB.
Changed motor control / Replaced MAB8420 by MAB8440
Servo-µP
If the servo µP MAB8420 is replaced by the MAB8440 it is
desirable to make the following changes.
Change C2217 to 3.3uF
Change C2218 to 15nF
Change R3255 to 22k
Change R3257 to 27k
Change R3260 to 56k
Change R3261 to 56k
D6253: BZX79/C7V5 added.
Pre-amplifier board + light pen (POS. VOLT. SH.)
With effect from version number A06, the PCB layout of the pre-amplifier
print has been changed and a new light pen is used in combination with
this.
The new light pen can be recognized by some red paint on the laser
mounting PCB.
Consequently, during repair, you may now be faced with the following
possibilities.
A1. Devices equipped with a preamplifier board with a version number
lower than A06 and a light pen not marked with paint.
If the preamplifier board is replaced by a version higher than A05,
the following change must be made:
Fit a 470ohms resistor between A111 and A113.
Before switching on the device, turn R3180 all the way to the right.
After switching on, carefully adjust the laser current with R3180.
A2. A light pen without a paint mark must be replaced with a light pen
with a paint mark.
No change necessary, however, before switching on R3180 must
be turned clockwise as far as possible.
After switching on, carefully adjust the laser current with R3180
B1. Devices equipped with a pre-amplifier with a performance number
A06 and above together with a marked light pen.
If the preamplifier board is replaced by one with a lower version
number than A06, R3180 must be turned all the way clockwise
before switching on the device. After switching on, the laser
current can then be carefully set with R3180.
B2. When replacing the light pen with a light pen without a paint mark,
the following change must be made.
Fit a 470Ω resistor between A111 and A113.
Turn R3180 fully clockwise before switching on and carefully
adjust the laser current with R3180 after switching on.
The new light pen will be delivered under the old order number.
To prevent unwanted high failure rates of light pens, it is used in a
number of devices. where positive supply voltage lasers are used the
laser current setting is increased to 800 mV (measured across R3308).
this in contrast to its current value (575 mV ± 75 mV).
With this type of laser, this increase has no consequences on the
expected service life.
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