Service manual

you wish to sample the system, a limited version of the database is maintained as a Viewdata system and
available on Cambridge [phone]. This contains a response frame allowing you to request information
on a full SID subscription.
SID has an electronic mail facility, allowing for messages to be passed between users. Mailboxes are
included for requests for return of goods, enquiries on 6502 and ARM based producs, MS-DOS, Econet
queries etc. SID subscribers can access a list of mailboxes for this purpose.
Acorn is dedicating considerable resources to providing these support routes. It is our belief that reinforcing
links between customers and local dealers has practical and commercial benefits for all concerned. Please
make use of both SID and the hot-line in answering customer enquiries. Customers should not be directed to
Acorn as we can only support authorised dealers and ASCs, although customers will be allowed to use SID.
Common problems section
External Second Processor Unit - Tube ULA
There has been instances where problems are experienced when an external 2nd Proc. is connected to the
TUBE port of a Master 128. This is due to timing problems present within the Ferranti Tube ULA situated in
the 2nd Processor which can be rectified by carrying out a small modification. This modification would only
be helpful when a second processor is known to work on a BBC 'B' and not on a Master 128, and the Master
128 will work with other second processors.
The Ferranti Tube ULA can be replaced by a Bipolar Tube Emulator PCB which eliminates the timing
difficulties experienced with Z80,6502,32016.
The new CMOS tube chip should be used for internal Master second processors - the Turbo and the 512
boards. It is not directly pin for pin compatible with the older Ferranti chip, and cannot be used directly in
external second processors.
Ferranti Tube ULAs should still be used for Acorn Cambridge Workstations.
the Acorn Part Nos are as follows:
CMOS Tube ULA 2201,266
Bipolar Tube Emulator PCB 0359,400
Ferranti ULA 0201,605
Doc. 999,0031 December 1987 -7- Acorn Engineering News