Service manual

H/Z-100 Service Bulletins
permit machine insertion of the part.
FSB-Z100-057: Z-100/RS-232 Modification
A situation may occasionally be experienced with ZW-110/120 models that requires
a modification to the RS-232 portion of the Main Board as follows:
- Symptom: Ports J1 and J2 do not function if modem is powered up prior to the Z-
100 being powered up.
- Analysis: Some modems have been found to place a negative voltage on the +12
V line from U228 on the motherboard. This keeps the +12v regulator from turning
on and the DTR line is in a transition state between On and Off.
- Solution: Install a diode, P/N HE 56-89, across C203 on Main Board. Note: The S-
100 card cage should be removed prior to the installation of the diode. It is
recommended to install the diode on the component side. The diode was installed in
production models as of August 1, 1983.
(Surprisingly, my newer motherboards, HE 181-5743, stamped 85-2806-1 in the
center, did not have this modification, but I have no idea as to their date of
manufacture - ed.)
Some other miscellaneous Field Service Bulletins that may be of interest:
FSB-DK-024: Z-207-41/42 8" Drive Configuration
Some confusion has arisen on the proper positioning of the MT/SR jumper on the 8"
floppy disk drives. When using the disk system with ZDS computers, make sure the
jumper is in the MT position. Also make sure the software you are using meets this
criteria: Z-DOS BIOS version 1.10, Format version 1.6 or higher, and/or CP/M
2.2.101 or higher. The use of older software will cause incompatibility with the disk
drive jumpering and BDOS and/or Format errors will result.
FSB-DK-025: H/Z-207 Erratic Write Operation
Circuit board #85-2807 for the H/Z-207 included base resistors for Q2 and Q3 to
eliminate any write irregularities. On older boards, if replacing Q2 and Q3 (#417-
937) does not correct the problem, install a 100 ohm resistor in series with the base
lead of Q2 and Q3. Install the resistors only when needed.
FSB-DK-027: Z-207 Controller Errors
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