Service manual

H/Z-100 Service Bulletins
FSB-Z100-047: CP/M Won't Boot Properly
The 12H6 PAL IC (HE 444-128) at U186 on the motherboard has frequently caused
the CP/M booting problems.
On the motherboard (HE 85-2653-1), check Y101 (10 MHz crystal, HE 404-645), for
proper frequency and output. Also, check U210 (8085 CPU, HE 443-1010) for poor
socket contact or defective IC.
FSB-Z100-048: "Interrupt Circuit Error - U208" Displayed on Power Up
or Appears Intermittently
On the motherboard, check the foil lead going to U114, pin 10. This foil is cut as a
modification, but may not have been completely removed. A small piece of this foil
might be touching U114, pin 7, causing the interrupt error.
FSB-Z100-049: "Timer Error - U160" Displayed on Power Up
or Appears Intermittently
On the motherboard, check U191 (4.00 MHz oscillator module, HE 150-132) for
proper frequency and output.
FSB-Z100-050: Z-120 Low Video Brightness
A defective U337 (HAL14H4, HE 444-115) or U329 (74SL174, HE 443-1053) on the
video board may cause this problem.
FSB-Z100-051: Z-120 Video Board Loads Motherboard
A defective U369 (82S129), HE 444-103), U370 (TBP18S22, HE 444-127), or U371
(82S129, HE 444-102) on the Z-120 video board may load down the motherboard.
FSB-Z100-052: Drive Cross-Reference
Most Z-100 computers used a generic number for the drives installed. In later
models, to ease identification of the drive(s) in each unit, a label was applied to the
computer rear panel showing the last three digits of the drive part number, with the
Winchester digits first.
"Drive Type 163" indicates an HE 150-163 drive is installed, while "Drive Type
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