Acorn BBC Master 128, Руководство по обслуживанию

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Master Series Service Manual
LK13 PCB track, made West: A to D converter reference select.
Two position link.
As shipped, this link is a track on the bottom of the PCB causing the
A to D converter reference voltage input to be 1.8V.
If the LK13 track is cut then the voltage reference must be applied
between analogue ground and Vref on the external connector.
If the LK13 track is cut and LK13 made East with a wire link, a
precision reference can be fitted in the position PR1 shown on the
circuit diagram.
LK14 PCB track, made: Serial data clock
reference. One position link.
As shipped, this link is a track on the PCB connecting the CHROMA chip
1.23MHz output to the Serial Processor. This link is provided for
production purposes and should not be modified.
LK15 PCB track, made West: PAL/NTSC
select. Two position link.
As shipped in the UK, this link is a track on the bottom of the PCB
causing the CHROMA chip to encode colour information on to the
television output in PAL format. If the track is cut and a wire link
used to make the other side of the link, then colour information will
be encoded in NTSC. In general, televisions within the UK can only
accept the PAL format.
LK16 wire link, not fitted: Chrominance information luma trap
bypass. One position link.
This link is not normally fitted. It is provided for those
applications where filtering of the luminance information from the
chrominance part of the television signal is not required.
LK17 : Not present.
LK18 plug, made West: Paged ROM/RAM
Select. Two position link.
When fitted in the West position, this link causes 16Kbyte of RAM to
appear in each of the "sideways" memory "slots" 6 and 7.
When fitted in the East position, a 32Kbyte ROM occupying slots 6 and
7 may be plugged into socket labelled 1C41.
10 Issue 1